Gerald F. Fletcher, M.D., received his M.D. degree and completed his residency and cardiology fellowship at Emory University in Atlanta, Georgia. Dr. Fletcher is currently Professor of Medicine (Cardiology) and Chairman of the Department of Rehabilitation Medicine at Emory. His primary research interest is exercise training and testing in cardiac rehabilitation. 146

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CURRENT STATUS OF CARDIAC l3EWABILITATION

Cardiac rehabilitation has become a very important modality in the current management of patients with cardiovascular disease. Patients who have cardiovascular events, particularly those with corona.ry artery disease, are often functional in society and employed prior to a cardiac event, and frequently require only “reentry” into their former life “pattern.” Therefore, rehabilitation must focus on this process of appropriate reentry, emphasizing all aspects of secondary prevention, including proper modification of coronary risk factors. Cardiac rehabilitation began primarily after infarction, but has evolved over the last 3 decades to begin after coronary artery bypass surgery or coronary angioplasty. Even patients with stable coronary artery disease with known coronary anatomy have undergone cardiac rehabilitation. The cardiac rehabilitative process involves many health professionals, led and directed by the physician. Nurses, physician assistants, exercise scientists, physical and occupational therapists, dieticians, psychologists, technologists, and oI.hers provide daily, compl.ete rehabilitative care. Cardiac rehabilitation and secondary prevention should lead to primary prevention in many patients’ families, particularly those with a strong family history and other risk factors for coronary artery disease. The incorporation of primary prevention in the overall rehabilitative process, and the involvement of the family of the patient with coronary artery disease, has become quite important. Such primary prevention involves the “hygienic” measures of weight control and physical activity, but more important, the evaluation of the level of blood lipids, particularly serum cholesterol. This single risk factor is probably the most influential in the development and progression of coronary artery disease. Substantial data show that control of blood lipid levels is imperative for c,ardiac rehabilitation and primary prevention to be successfuL1 Because the current hospitalization time for cardiac patients is slhort, only limited inpatient rehabilitation can be done. Basic patient and family education and early ambulation are begun; the majority of rehabilitation is done on an outpatient basis. Therefore, this Curr

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monograph will review the current status of outpatient cardiac rehabilitation, beginning with a description of the comprehensive nature of the rehabilitative process. An important section on exercise testing and its role in cardiac rehabilitation will be followed by exercise training programs, with a review of exercise training in supervised groups at home, and in the workplace. Also included are sections on the various types of training modalities used in aerobic and isometric activity, blood lipid control, which is a major thrust in the cardiac rehabilitative process, and other coronary risk factors that are addressed and modified in the cardiac rehabilitative process. Lastly, special populations will be addressed: patients on beta blockade, the physically handicapped, patients with heart failure, ventricular arrhythmias, peripheral vascular disease, and diabetes mellitus, and the elderly. All of these patient categories are frequently seen in cardiac rehabilitation programs and often need collaborative medical follow-up by a physiatrist, general internist, peripheral vascular specialist, endocrinologist, gerontologist, or other specialists of medicine involved in the care of these patients.

COMPREHENSIVE

CARDIAC

BEHABILITATION

Over the last 2 decades, cardiac rehabilitation, or secondary prevention, has evolved into a comprehensive management strategy. Originally focusing on exercise training, these programs have evolved to emphasize overall risk factor and behavioral modification, and to include the family and significant others as part of the total approach. Successful cardiac rehabilitation requires overall care of the patient by the cardiac rehabilitation health professionals, along wit.h the referring primary physician and the cardiologist or cardiovascular surgeon who have been treating the patient, Comprehensive cardiac rehabilitation specifically entails the modification of coronary risk factors, particularly the control of abnormal blood lipids levels (blood cholesterol). It is important for the dietician to assist patients in weight loss and provide dietary guidelines. The input of the physician and well-trained nurse in the daily, longterm care of patients’ other medical problems, such as musculoskeleta1 diseases, arthritis, peripheral vascular disease, diabetes mellitus, reaction to medications, and problems with aging, is also important because these are all components of the comprehensive approach addressed by health professionals. Back-to-work status and vocational rehabilitation are very important components of cardiac rehabilitation programs and these factors must be addressed by the primary physician. Patients in such programs are seen regularly by the cardiac rehabilitation team and, therefore, often relate much better to the health care professional in 148

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this setting than with their private physician. The overall impact of patient care is much more effective, in many instances, in the cardiac rehabilitative setting. ‘The comprehensive nature of this management has made it a very important area of care for the patient’s family. In cases of genetically induced lipid abnormalities, children and other family members needing entry into the health care system may initially be seen through the cardiac rehabilitation program in which a family member is involved. Therefore, the entire family often becomes involved with areas of prevention in health care for the first time when a family member enters a cardiac rehabilitation program. Thus, the comprehensive approach in cardiac rehabilitation is state of the art. As patients live longer and develop more medical complications related to their cardiovascular disease, comprehensive care will have an increasing impact to our health care system in the future. EXERCISE

TESTING

IN CARDIAC

REHABILITATION

The exercise test in cardiac rehabilitation is a vital component of the overall rehabilitative process. It provides continuous follow-up in a noninvasive manner and adds information to the overall physical evaluation. In general, testing is performed before entering the cardiac rehabilitation exercise program, usually 3 to 6 months after the initial test and the initial part of the training program, and at least every year thereafter. The test provides information on diagnosis of changes in “cardiac status,” prognosis, exercise capacity, and evidence of training effect-valuable information for both the health professional and the patient. The exercise test is usually done without echocardiographic, nuclear, or other additional studies:. The hemodynamic and electrocardiographic indices, with the functional indices in the form of oxygen consumption measurements, provide a sound basis for patient follow-up, are relatively inexpensive and noninvasive, can be done on an outpatient basis, and are time-efficient. TESTING PROCEDURES The Physician’s Role Exercise testing should only be conducted by well-trained personnel with a basic knowledge of exercise physiology. Physicians and other health professionals (especially nurses) familiar with normal and abnormal responses during exercise are most qualified. Equipment and medications for cardiopulmonary resuscitation (CPRI must be readily available. Although exercise testing is considered Curr

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safe, there are some reports of acute infarctions and deaths related to the procedure. Several surveys confirm that up to 10 myocardial infarctions, deaths, or both can be expected per 10,000 tests. Risk is greater in the postmyocardial infarction patient and in those being evaluated for high grade ventricular arrhythmias. Table 1 lists three classes of complications that may develop with exercise testing. Good clinical judgment is imperative in determining indications for and contraindications to exercise testing. Table 2 lists absolute and relative contraindications to exercise testing and Table 3 cites reasons to reschedule an exercise test. As stated in the American Heart Association (AHA) Exercise Standards,’ exercise testing should be performed under the supervision of a physician who is appropriately trained to conduct exercise tests. The physician should be responsible for ensuring that the exercise laboratory is properly equipped and that testing personnel are appropriately trained. The level or degree of immediate supervision needed during a test can be determined by the clinical status of the patient being tested. The physician or physician’s staff should ask pertinent questions about the patient’s medical history, perform a brief physical examination, and review the standard 12-lead electrocardiogram (ECG) performed immediately before testing. The physician should interpret data derived from testing, suggest further evaluation or therapy, and help provide effective and timely adTABLE 1. Complications

of Exercise Testing

Cardiac Bradyarrh”ythmias Sinus Atrioventricular junctional Ventricular Atrioventricular block Asystole ‘Tachyarrhythmias Fast supraventricular Ventricular Ventricular fibrillation Myocardial injury-infarction Congestive heart failure Hypotension and shock Noncardiac Musculoskeletal trauma Miscellaneous Dizziness Fainting General malaise and body aches Fatigue sometimes persisting for days 150

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TABLE

2.

Contraindications Absolute

to Exercise Testing Relative*

Recent acute myocardial infarction or other significant change on resting electmcardiogram Unstable angina Serious cardiac arrhythmias Acute pericarditis Acl.ive endocarditis Severe aortic valvular stenosis Severe left ventricular dysfunction Acute pulmonary embolus or infarction Significant noncardiac illness Severe physical or psychological disability

Less serious noncardiac

illness

Significant arterial or pulmonary hypertension Tachyarrhythmias or bradyarrhythmias Moderate valvular or myocardial disease Drug effects or electrolyte abnormalities Left main coronary obstruction or its equivalent Obstructive cardiomyopathy Psychiatric disease

'Under certain circumstances and with appropriate precautions, subjects with relative contraindications may be tested.

vanced CPR when necessary. A defibrillator and appropriate medications should also be available. Table 4 specifies safety measures for ex.ercise testing. There is considerable difference between the body’s response to acute exercise in the supine and erect positions. In healthy persons, stroke volume and end-diastolic volume change very little during supine cycle exercise from volumes obtained at rest, whereas in the erect position, these values increase and i.hen plateau during mild wlork. In patients with intrinsic cardiac abnormalities, left ventricular filling pressure is more likely to increase during exercise while supine than while erect. When patients with angina pectoris perform identical submaximum cycle work in the supine and erect positions, heart rate is higher in the supine position. Maximum work performed, however, is lower in the supine position, and angina de&lops at a lower rate pressure product. ST segment depression is usuTABLE

3.

Reasons to Reschedule an Exercise Test 1. Subject did not fast for 2 hours before the test. 2. Subject having acute, temporary musculoskeletal problems. 3. Electrocardiogram suggests infarction of uncertain age; no other clinical data available. 4. Subject donated blood in last 24 hours. 5. Subject under influence of psychoactive medication. 6. Not all monitoring and safety equipment functioning pmperly. Cwr

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TABLE 4. Safetv Measures for Exercise Testing 1. .4 definite plan of emergency action, including clarification of the duties of each Imember of the team which, in addition to direct patient care, also includes Inotification of appropriate individuals and securing an elevator and other necessities lfor patient transfer. 2. Prearrangement for rapid admission to a critical care unit. 3. ,411members of team trained in cardiopulmonayv resuscitation. 4 Defibrillator within cable reach of treadmill, on and charged during test. IFull tube of Ielectrode paste on top of unit.l 5. Emergency drug kit stocked and maintained lantiarrh,vthmics, pressor agents, and Imiscellaneous). 6. Intravenous solutions, administration sets, needles, and yringes. 7 13rupharyngeal airways, laryngoscope, endotracheal tubes, ventilation bag, and suction machine. 8. Oxygen administration equipment. -

ally greater in the supine position because of the greater left ventricular volume; however, ST changes occur more frequently while upright than while supine. These differences must be considered if certain patients are tested in other than the usual upright treadmill position. Prc3tocols

Protocols for exercise testing should include an initial low load (warm-up), progressive, uninterrupted exercise with an adequate duration in each level, and a recovery period. For cycle ergometry, the initial power output is usually 10 or 23 W (150 kpm/minJ, normally followed by increases of 25 W every 2 or 3 minutes until symptomatic or “signomatic” end points are reached. If arm ergometry is substituted for cycle leg ergometry, a similar protocol may be used, except that initial power output and incremental increases are lower. Two-minute stages are most popular with arm ergometry.“’ 4 With arm exercise, blood pressure responses may be higher than with leg exercise, a factor that should be considered in certain patient subsets. Several treadmill protocols are in use, the most popular of which is the Bruce protocol. The advantages of the Bruce protocol include a seventh or final stage that cannot be completed by most individuals, and its use in many published studies provides extensive data for comparison. Its disadvantages include large increments in work 1oa.d that make estimation of maximal oxygen consumption (VO, max) less accurate. Some subjects are forced to stop prematurely because of musculoskeletal difficulties or inability to tolerate the high work load increments. An initial zero and one-half stage (1.7 mph at 0%, then 5% grade) may be used for some patients. Many exercise 152,

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testing labbratories currently use Balke-type protocols (e.g., Naughton, Stanford, McHenry) with metabolic equivalent (MET)41 MET equals 3.5 ml/kg/min of oxygen consumed) levels for stage advances. Regardless of the technique used, the optimum protocol should last 6 to 12 minutes and should be adjusted to the patient. Because there is strong evidence that the level of exercise required to produce ischemia is an important aspect of the exercise test result, how should the exercise test work load shall be selected? There is overwhelming agreement on use of a progressively increasing exercise protocol beginning with a stage low enough for the weakest candidate to tolerate for testing, with the highest stage being sufficiently difficult to challenge the best conditioned candidate. Each stage should last long enough for the body to reach or closely approach steady state, and the work increments from one stage to the next should be small enough to permit the desired degree of precision in estimating work capacity. The Bruce treadmill protocol (with some modification in the cardiac rehabilitation setting) is widely used (Tab1.e 51, and typical work output requirements for each stage in terms of oxygen consumption have been determined.’ To increase applicability, two easier stages may be added below stage 1 in order to accommodate virtually all ambulatory individuals.6 In order for measurements of treadmill performance, exercise time, or rate-pressure response to be directly related to the actual cardiac work involved, the subject must have reached or closely approached “steady state.” This implies that if the subject continued to exercise at this same intensity, cardiac output, heart rate, and other indices would stay TABLE 5. Schedule of Treadmill Time Pet Stage Stage Number

Exercise for the Graded Exercise Test’ Elapsed Time at End of Stage lminl

Speed km/H

(mph)

Treadmill Grade (‘%I

Slope Elevation 0 (degrees]

Zemt 3* 1.7 0 ILevell 0 ILevelJ 2.7 One-half+ 3* 1.7 5 2.7 2.8 First 3 1.7 10 5.7 2.7 6 12 Second 4.0 2.5 6.8 Third 9 5.5 3.4 14 8.0 Fourth 12 4.2 16 6.8 3.0 Fifth 15 18 8.0 5.0 10.0 18 8.9 5.5 20 11.0 Sixth Seventh 21 9.6 6.0 22 12.4 ‘From Sheffield LT: Exercise stress testing, in Fletcher GF ledi: f:,wrcise UI the Pracficc of,Wedicine. Mt Kisco, NY, Futura Publishers, 1988, p 52. Used by permission. tBegin with stage zem OPstage one-half if appearance and demeanor of subject suggest that walking capacity is severely limited. *E.xercise time in these preliminary stages is not counted when tabulating functional capacity Car-r Probl

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essentially the same until the point of fatigue. Steady state attainment requires at least 3 minutes, and perhaps longer on the treadmill, and exercise times shorter than this will not give a reliable reflection of cardiovascular capacity. Rather than assign a certain stage of exercise protocol based on age, history of exercise participation, or level of conditioning, it is preferable to require the subject to exercise progressively through the protocol until it becomes excessively uncomfortable or impossible to continue, i.e., to an end point of exhaustion unless other terminating end points occur. There are several ways of gauging whether or not the subject makes a good effort so that the exercise time is a true representation of physical capacity. The most obvious criterion is heart rate, which can be predicted with about 90% accuracy.6j ’ Perceived Exertion The subjective rating of exertion perceived by the person exercising is a good indicator of relative fatigue and has been used to subjectively quantify effort during exercise. Rather than using heart rate alone to clinically determine intensity of exercise, the 6 to 20 Borg scale of perceived exertion ’ is useful (Table 6). Special verbal and written explanations about the rating of perceived exertion are available and in use. Although some variation exists among patients in their actual rating of fatigue, they seem to rate consistently from test to test. Thus, the Borg scale can assist the clinician in judging de-

TABLE

6.

Borg Scale for Rating Perceived Exertion* IS-Grade Scale 6

7 Very very light 8

9 Very light IO 11 Fairly light 12 13 Somewhat hard 14

15 Hard 16 17 Very hard

IO-Grade Scale 0 0.5 1 z 3 4 5 6

Nothing Very very weak ljust noticeable1 Very weak Weak (lighti Moderate Somewhat strong Stmng (heayl

7 8

Very strong

9 10

Very,

Very strong lalmost maximum1

18

19 Very very hard

0

Maximum

20 ‘From Pollock ML, Wilmore JH: E,xercise tion and Rehabilitation, ed 2. Philadelphia,

154

in Health and Disease: Emluation and Prescription,for WB Saunders, 1990, p ?YO. IJsed by permission.

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gree of fatigue with testing and correlate the level of fatigue testing with that experienced during daily activities. INDICATZONS Indications from clinical Absolute

FOR TERMINATING for discontinuing experience.

during

EXERCISE TESTING an exercise

test have been derived

Indications

Drop in systolic blood pressure (persistently below baseline) despite an increase in work load. New onset of or increasing anginal chest discomfort. Central nervous system symptoms tie, ventricular such as ataxia, dizziness, or near syncopel. Evidence of poor peripheral perfusion (cyanosis or pallor). Certain arrhythmias (multiform complexes, triplets, and runs). Technical difficulties in monitoring the ECG or systolic blood pressure. Patient’s request to stop.

l

l l

l l l

l

Relative Indications l

l l

l l l

ST or QRS changes such as excessive (2 3 to 4 mm) ST displacement or marked QRS axis shift. Increasing chest discomfort. Fatigue, shortness of breath, wheezing, leg cramps, or leg claudication. General appearance. Less serious arrhythmias, including supraventricular tachycardias. Development of bundle branch block that cannot be distinguished from ventricular tachycardia.

POSTEXERCISE PERIOD Some abnormal responses occur only during recovery after exercise. If maximum sensitivity is to be achieved with an exercise test (especially in those with cardiovascular disease), patients should be supine in the postexercise period; however, many physicians prefer the sitting position for maximum patient comfort. Monitoring and recording of blood pressure and ECG results should continue for at least 6 to 8 minutes after exercise. An abnormal ECG responses occurring only in the recovery period is not unusual, and mechanical dysfunction with electrophysiologic abnormalities in the ischemic ventricle after exercise can persist from minutes to hours. Curr

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155

INTERPRETATION Clinical

OF THE EXERCISE TEST

Responses

Symptoms.-Classical ischemic chest discomfort induced by the exercise test is strongly predictive of coronary artery disease and is even more predictive with ST depression. It is important to have a careful description of the discomfort from the patient to ascertain that it is typical angina. After the subject has begun exercise, a continuing dialogue should take place between the test supervisor and the subject. Questions such as, “Do you have any unpleasant feeling in your chest? Is your breathing OK? Does anything bother you?” should be included in the conversation. When any symptom is reported for the first time, it should be entered in the exercise test record with subsequent follow-up. The test subject must be convinced that the supervisor is sincerely interested in the exercise-induced symptoms and has a receptive attitude to all questions. Questions should be asked in an encouraging voice with entries written on the work sheet. Patient’s Appearance.-General appearance is helpful in clinical assessment. A decrease in skin temperature, cool perspiration, and peripheral cyanosis during exercise may indicate poor tissue perfusion resulting from inadequate cardiac output with secondary vasoconstriction. Higher work loads should not be encouraged in such patients. Neurologic manifestations such as lightheadedness or vertigo can also indicate inadequate cardiac output. Physical Ezamination.Cardiac examination immediately after exercise can provide information about ventricular function. A precordial bulge or gallop rhythm can result from left ventricular dysfunction. A mitral regurgitant murmur suggests papillary muscle dysfunction related to transient ischemia. Exercise or Functional Capacity Maximal oxygen consumption is a measure of the functional limit of the cardiovascular system and the best index of exercise capacity. A decrease in maximum cardiac output is the major hemodynamic consequence of coronary artery disease, causing a decrease in exercise capacity. Although many patients may limit exercise because of angina1 pain, acute reduction in left ventricular output resulting in decreased stroke volume and resultant increasing pulmonary artery pressure appear to be the mechanisms limiting cardiac output. If patients with coronary artery disease reach 13 METS, their prognosis is good, regardless of other test responses. In patients with an exercise capacity of less than 5 METS, subsequent mortality is higher than in those with higher capacities. A normal exercise capacity, 156

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however, does not exclude severe cardiac impairment. Mechanisms proposed to explain a normal exercise performance in such patients include increased peripheral oxygen exuaction, preservation of ch.ronotropic reserve, ability to tolerate elevated pulmonary wedge pressures without dyspnea, and increased levels of plasma norepinephrine at rest and during exercise. HEMODMVAMIC

RESPONSES

Blood Pressure Blood pressure is related to cardiac output and peripheral resistance. Systolic blood pressure at maximum exertion is considered a chnically useful index of cardiac contractility (inotropic capacity). Although some normal subjects have a transient drop in systolic blood pressure at maximum exercise, this finding is frequently associated with severe coronary artery disease and ischemic dysfunction of the myocardium. Exercise-induced hypotension also identifies patients at increased risk for ventricular fibrillation in the exercise laboratory. Figure 1 reveals various blood pressure responses to exercise. Heart Rate A relatively rapid heart rate during submaximum exercise or recovery could be caused by vasoregulatory asthenia, decreased vascular volume or peripheral resistance, prolonged bed rest, anemia, or metabolic disorders, and thus may not reflect intrinsic cardiac disease. This finding is also relatively frequent soon after myocardial infarction or coronary artery surgery. Relatively low heart rate at any point during submaximum exercise could be caused by exercise training, enhanced stroke volume, or drugs. The common use of beta-blockers, which decrease heart rate, may complicate the interpretation of heart rate response to exercise. Conditions that affect the sinus node (usually disease of the right coronary artery) can also attenuate a normal heart rate during exercise testing. E CG RESPONSES Normal

Response

J-Junction Depression.-The J-junction is depressed in the lateral leads at maximum exercise, then gradually returns to pre-exercise values in recovery. A dramatic increase in J-junctional depression may be observed in all leads and is greatest at 1 minute into recovery. Subjects with resting J-junction elevation may develop an isoelectric J-junction with exercise, a normal finding. These changes return to pretest values later in recovery. The normal ST segment vector response both to tachycardia and exercise is a shift to the right Curr

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157

3 6 x - Normal response 13% minutes, drops of normal exercise l

9

12

15

subject able to exercise blood pressure at peak capacity.

- Abnormal - subject increases systolic pressure initially, but pressure drops early in exercise before normal exercise capacity is reached.

A- Abnormal - subject fails to rarse systolic pressure to 130 mmHg or higher,even though exercise duration may be nearly normal. FIG 1. Normal and abnormal systolic blood pressure responses to exercise tests. (From Sheffield LT: Exercise stress testing, in Fletcher GF (ed): Exercise /n the Practice of Medicme. Mt. Kisco, NY, Futura Publishers, 1988, p 75. Used by permisslon )

and upward. Considerable shift appears evident. Abnormal

biologic

variation

in the degree of this

Responses

ST Segment Changes.-The ST segment level is measured relative to the PR segment as the U-P segment is usually unclear during exercise. ST elevation is measured as the deviation from the baseline ST level, and ST depression is measured from the isoelectric PR level. If the baseline ST segment is depressed, the deviation or difference from that level to the level during exercise or recovery is considered. The point for measuring the ST level is the J-,junction, and points beyond this (60 or 80 msecl should only be used if the ST segment slope is horizontal or downsloping. Considering rapidly upsloping ST depression as abnormal increases sensitivity but decreases specificity. Many ST scores have been recommended, but in most populations, none have been validated as superior to standard “visual” 158

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19%

measurements by the experienced health professional. Exercise-induced myocardial ischemia can result in one of three ST segment displacements on the surface ECG: depression, elevation, and normalization. ST Segment Depression.-ST segment depression is the most common manifestation of exercise-induced myocardial ischemia. It usually reflects diffuse subendocardial ischemia, with vector direction determined largely by the placement of the heart in the chest. Th.e standard criterion for this abnormal response is horizontal or downsloping ST segment depression of 0.10 mV (1.0 mm) or more for 80 msec in at least three consecutive isoelectric or ‘level” complexes. However, as shown in Figure 2, other criteria have been considered. Downsloping (divergent) ST segment depression usually reflects more ischemia than horizontal depression. In the presence of baseline abnormalities (especially in patients on digitalis), exercise-induced ST segment depression is less specific for ischemia. Factors related to the probability and severity of coronary artery disease include the degree of abnormality, time of appearance, duration, persistence in recovery, and number of leads with ST segment depression. The lower the work load and double product at which the ST chlange occurs, the worse the prognosis and the more likely the presence of multivessel disease. ST Segment Elevation.-ST elevation must be judged by whether it occurs over Q waves of a previous myocardial infarction or is un-

FIG 2. Abnormal ST responses. (From Froellcher VF: Exercise and the Heart: Clinical Concepts. Chlcago, Year Book Medical Publishers, 1987, p 46 Used by permission.) Cwr

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related to Q waves. ST segment elevation has been more frequently observed in anterior leads (V, and V,) with Q waves.’

ST

Segment

Elevation

Over

Q

Waves

of

Myocardial

Infarction.-Previous myocardial infarction is the most frequent cause of ST segment elevation during exercise and seems related to dyskinetic areas or ventricular aneurysms. Approximately 50% of patients with anterior and 15% with inferior myocardial infarction exhibit this finding during exercise. Patients with elevation usually have a lower ejection fraction than those without elevation over Q waves. These changes may result in reciprocal ST depression simulating ischemia in other leads. ST segment elevation and depression that develop during the same test may indicate multivessel coronary artery disease.

ST Segment Elevation Without Q Waves.-In patients without previous Q wave myocardial infarction, ST segment elevation during exercise frequently reflects severe transient ischemia resulting from significant proximal luminal disease or (in some cases) coronary spasm. In patients with variant angina, ST segment elevation usually occurs during spontaneous angina1 episodes, frequently while the patient is at rest. During exercise, ST segment elevation has been reported in about 30% of these patients and a reversible thallium-201 perfusion defect usually corresponds to the site of ST elevation. ST Segment Normalization or Absence of Change.-Another manifestation of ischemia may be normalization of or no change in the ST segment. ECG abnormalities at rest, including T wave inversion an’d ST segment depression, reportedly return to normal during attacks of angina and during exercise in some patients with myocardial ischemia. Such abnormalities, however. can also be observed in subjects with a “persistent juvenile pattern” on the resting ECG. Diagnostic Value of R Wave Changes Exercise-induced changes in R wave amplitude have not improved diagnostic accuracy despite use of several lead systems, clinical subsets of patients, and different criteria for an abnormal response. T Wave Changes.-In normals, a gradual decrease in T wave amplitude is observed in all leads during early exercise, but with maximum exercise the T wave begins to increase. At l-minute recovery, amplitude is near equivalent to resting values. T wave changes are of limited value in the diagnosis of ischemia.

I/ Wave Changes-U wave inversion may be associated with left ventricular hypertrophy, coronary artery disease, and aortic and mitral regurgitation. These conditions are associated with abnormal left ventricular function. Exercise-induced U wave inversion in pa160

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tients with a normal resting ECG appears to be a marker of myocardial ischemia and suggests left anterior descending coronary artery disease. U wave changes may, however, be too difficult to assess with exercise increases in heart rate and the resulting proximity of the T and P waves. The sensitivity and specificity of exercise-induced ST segment depression can be demonstrated by comparing the results of exercise testing and coronary angiography.” With such, the exercise test with 0.1 mV (1 mm) horizohtal or downsloping ST segment depression has approximately 84% specificity for angiographically significant coronary artery disease; that is, 84% of those without significant angiographic disease have a normal exercise test. These studies had a mean 66% sensitivity of exercise testing for significant angiographic coronary artery disease, with a range of 40% for one-vessel di,sease to 90% for three-vessel disease. P~iOGNOS’TZC USE OF THE EXERCISE TES7 Prognostic use of exercise testing is important in cardiac rehabilitation for two reasons. The first is to provide reliable answers about the probable outcome of a cardiovascular illness. The second is to identify patients in whom interventions might improve eventual outcome. Several patient groups have been studied to determine prognosis with exercise testing, including postmyocardial infarction patients, those with stable coronary artery disease (including silent ischemia), patients who become symptomatic after coronary artery bypass surgery, patients after percutaneous transluminal coronary angioplasty (PICA), and asymptomatic individuals.

Postmyocardial Infarction Patients Symptom or sign-limited end points are sometimes used 2 or 3 weeks after myocardial infarction. However, a submaximum limited test is quite appropriate. A heart rate limit of 130 to 140 beats/min and a MET level of 5 to 7 is arbitrarily used and a Borg perceived exertion level in the range of 13 to 15 can be used as a test end point, particularly for patients receiving beta-blockers. A maximum test is probably more appropriate more than 3 weeks after myocardial infarction, when the patient is ready to resume full activities and become active in a cardiac rehabilitation exercise program. One review of numerous predischarge and postmyocardial infarction exercise tests reported few serious complications: two cases of recurrent infarction and two cases of ventricular fibrillation, one fatal, representing 0.05% morbidity and 0.02% mortality.‘l In studies of exercise testing after myocardial infarction with a follow-up for cardiac end points, tested patients were consistently at lower risk than Ourr Probl Cardiol, March

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161

those not tested, regardless of criteria used for testing,” thus supporting the clinical judgment of the skilled clinician. Using general criteria, only an abnormal systolic blood pressure response or a low exercise capacity were significantly associated with poor outcome. W:hen the studies were subgrouped by whether testing was done before or after discharge from the hospital, a high proportion of predischarge test results indicated poor outcome. Submaximum testing resulted in the highest proportion of positive associations and the highest risk ratios, and abnormal responses at higher work loads were not as predictive as those at lower work loads.”

Patients With Stable Coronary Artery Disease Exercise test data of patients with stable coronary artery disease help predict angiographic findings, cardiac events in those with silent ischemia, or improved survival with coronary artery bypass surWY.

Angiographic Findings.- Numerous studies have provided evaluations to predict left main or triple-vessel disease or both.‘” Different criteria have been used with varying results. &ertional Hypotension.- In most studies, exercise-induced hypotension indicates a poor prognosis, with a predictive value of 50% for left main/triple-vessel disease.13 Exercise-induced hypotension can occur in patients with coronary artery disease, valvular heart disease, or cardiomyopathy. b D. McCall: Numerous studies have shown that symptom limited exercise testing can be carried out safely prior to hospital discharge, in the majority of patients who have sustained an acute myocardial infarction (Current Problems in Cardiology, November 19911. In this setting it is probably preferrable to use a low level exercise protocol, such as a Naughton Protocol, the symptom limited exercise testing being carried out between 7 and 10 days following the infarction. As is pointed out by the author this may have considerable psychologic benefit to the patient by demonstrating, under controlled circumstances, that he/she is capable of exercise without untoward effect. Exercise testing at this time has the added benefit of allowing patients to be separated into low and high risk subsets. This is especially true when the exercise test is accompanied by Thallium scintigraphy. By so risk stratifying patients, with a pm-discharge exercise test, it is possible to individually tailor therapy and to selectively employ coronary arteriography for those in whom it is deemed appropriate (Current Problems in Cardiology, November 1991). -

lmproved Survival After Coronary Artery Bypass Surgery.-One study suggests that patients with cardiomegaly, exercise capacity of less than 5 METS, or a maximum systolic blood pressure of less than 130 mm Hg are more responsive if treated with surgery.” In another trial, patients who had an exercise test response of 1.5 mm of ST segment depression showed enhanced survival with surgery, and im162

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proved survival also applied to those with baseline ST segment depression and those with claudication.15 In a.nother,‘” surgical benefit with regard to mortality was greatest in patients with 1 mm ST segment depression at less than 5 METS.

,Patients Who Become Symptomatic Ajler Coronary Artery Bypass Surgery.-Several studies have evaluated graft occlusion and recurrence of symptoms; however, exercise-induced ST depression does not predict prognosis after coronary artery bypass surgery. An exercise capacity of 9 METS or more, however, indicates a good prognosis, regardless of other responses,17 and these patients do very well in cardiac rehabilitation. Patients Afler PTCA.-Exercise testing may be of value in the routine (6- to 12-month) follow-up of patients who have undergone PICA, especially in the evaluation of chest discomfort and detection of restenosis. Testing is of particular benefit in the cardiac rehabilitative setting and may be more helpful in the patient with symptoms suggestive of ischemia or the patient whose progress in rehabilitation is limited.

FIJNCTIONAL.

CLASSIFICATION

OF DISABIl.ITY

Exercise testing is used to determine the degree of impairment and disability of patients with various forms of heart disease. Patients who “exaggerate” their symptoms or who have a psychological impairment can often be identified. VO, max is the best noninvasive measurement of the exercise capacity of the cardiovascular system. without signs or Inability to reach 5 METS (below 18 ml-kg-‘amin-‘1 symptoms is a criterion of disability used by the Social Security Administration. Determination of a patient’s exercise capacity affords an objective measurement of the degree of cardiac impairment.” Such functional classification is addressed on occasion in a cardiac rehabilitation program.

C4RDlAC ARRHYTHMIAS E,xercise-Induced Ventricular Arrhythmias In patients with coronary artery disease, exercise-induced ventricular arrhythmias are not considered an independent risk factor for subsequent mortality or coronary events. However, recent data suggest that these arrhythmias add independent prognostic information to thallium-201, ST segment, and heart rate changes,lY, ” and are associated with severe coronary artery disease and wall motion abnormalities. Exercise testing in cardiac rehabilitation may be of Cm-

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163

considerable value in evaluation of drug therapy of ventricular arrhythmias, particularly in subjects with coronary artery disease. Exercise may induce cardiac arrhythmias under several conditions, especially diuretic and digitalis therapy,21-23 and recent ingestion of alcohol or caffeine may exacerbate exercise-induced arrhythmias. Because exercise increases myocardial oxygen demand, in the presence of coronary artery disease myocardial ischemia could predispose the patient to arrhythmias during exercise. Exercise-induced arrhythmias are generated by enhanced sympathetic tone, increased myocardial oxygen demand, or both. The immediate postexercise period is of particular concern because of high catecholamine levels that may be associated with a generalized vasodilation. Peripheral arteriolar dilation induced by exercise, and reduced cardiac output resulting from diminished venous return secondary to sudden termination of muscular activity may lead to a reduction in coronary perfusion while heart rate is elevated. The associated increased sympathetic tone in the myocardium may stimulate ectopic Purkinje pacemaker activity by accelerating phase 4 of the action potential, provoking spontaneous discharge and leading to increased automatic@. Exercise can, at times, suppress cardiac arrhythmias present at rest. This phenomenon has been attributed to the overdrive suppression of the ectopic impulse formation by sinus tachycardia induced by exercise-vagal withdrawal and increased s,ympathetic stimulation. Eictopic ventricular contractions are the most frequent cardiac arrhythmia occurring during exercise, followed by supraventricular arrhythmias. Their prevalence is directly related to age and cardiac abnormalities. In general, ectopic ventricular contractions are cause for concern in patients with known severe ischemia. Sinus arrhythmias, with periods of sinus bradycardia and wandering atrial pacemaker, are relatively common during exercise and the immediate recovery phase. Atria1 ectopy can occur in either normal or diseased hearts. Exercise-induced transient atrial fibrillation and flutter occur in less than 1% of individuals who undergo exercise testing.24 These arrhythmias may be induced by exercise in healthy individuals or patients with rheumatic heart disease, hyperthyroidism, pre-excitation syndromes, or cardiomyopathy. Paroxysmal atrioventricular junctional tachycardia is rarely observed during exercise. Exercise-induced supraventricular arrhythmias alone are usually not related to coronary artery disease but are more often related to pulmonary disease, recent alcohol ingestion, or excessive caffeine. In summary, the exercise test is a very thorough evaluation of the cardiovascular status of the patient in an ongoing cardiac rehabilitation program. It provides data on diagnosis and functional capacity. This information is most important in the daily evaluation and fol164

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1992

low-up of the patient, as well as in adjusting the exercise prescription for the appropriate level of exercise in the overall rehabilitative process. b GA. Beller: We almost routinely perform predischarge submaximal exercise testing after acute myocardial infarction in conjunction with myocardial perfusion imaging with either thallium-291 or T-99m sestamibi (cardiolitel. We believe that high and low risk subsets can better be separated by radionuclide and ECG stress test variables in combination compared to ECG stress testing alone. Patients with solely fixed defects confined to the infarct zone have an excellent prognosis, whereas patients demonstrating perfusion abnormalities in more th(an one vascular supply region or redistribution defects within or remote from the infarct zone have an increased cardiac event rate during follow-up. Patients with increased lung thallium-201 uptake on the post-exercise images are at significant risk for subsequent cardiac events. The exercise ECG is often nondiagnostic for ischemia because of resting ST-T abnormalities. Also, ST depression m,ay not be elicited at submaximal heart rates and workloads. EAXERCISE

TRAINING

Exercise training is useful in the management of patients with coronary artery disease because the physiologic changes that take place lessen ischemia at rest and during submaximum exercise.’ Physical activity is also associated with protection from development or progressionz5 of coronary artery disease. Although physical working capacity increases with training when heart disease is present, physiologic changes have differed somewhat from those reported in apparently healthy individuals and are outlined next. A4aximum Oxygen Uptake.-In patients with coronary artery disease, VO, max increases with training. The magnitude of the change is less in those with heart disease than observed in apparently healthy individuals, but the increase is noteworthy and the maximum heart rate may be the same or slightly greater after training in those with heart disease.26 The least increments are seen in individu,als with heart failure, but even in these patients the improvement is of great rehabilitative value for restoring the ability to perform daily activities. Cardiac Output.-The increase in maximum cardiac output is the result of an increase in both stroke volume and maximum heart rate. In patients with cardiac disease, the submaximum cardiac output may be lower with maintenance of oxygen consumption (VO,l by widening the arteriovenous oxygen difference after training.27 Such a result suggests improved overall efficiency for delivery of oxygen to the tissues. Decreased

Myocardial

cial significance Cut-r t’robl

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in individuals March

1992

Uptake.Exercise training has spewith coronary artery disease because 165

the changes promote lower myocardial oxygen uptake (MO,J. Changes associated with lower MO, are decreased heart rate, lower circulating catecholamines, and lower systolic blood pressure. The benefits of these adjustments can be demonstrated by the greater amount of work that can be done before angina or ECG-determined ST depression occurs.”

GENERAL PRINCIPLES OF PRESCRIPTlVE EXERCISE Exercise intensity should approximate 50% to 85% of VO, max based on the exercise test. The steps in this process are as fol1OlNS : 1. Prescription from the exercise test can be determined by finding the highest work load achieved on the exercise test, and considering the training heart rate for dynamic exercise as that which occurred at the work load, which was 60% to 90% of maximum heart rate, or 50% to 85% of heart rate reserve IImaximum heart rate resting heart rate1 X 50-85%) + resting heart rate. 2. Activities can be prescribed as the work intensity that achieves the training heart rate after 5 to 10 minutes at that work load (steady sta.teJ. This may be expressed as watts on an ergometer, speed on a treadmill, or in METS. 3. If an individual cannot assess intensity, then heart rate counting (manually or with a cardiotachometerl is useful. Heart rate counters are widely available and are fairly accurate for low to moderate intensity exercise. 4. Individuals can also judge the intensiv of exercise as the rating of perceived exertion, which can be equated to desirable heart rate during laboratory exercise and to their activities. The original scale is a 15grade category scale ranging from 6 to 20, with a verbal description at every odd number (see Table 6). The following rating of perceived exertion values should be considered: Cl.2 light, 40% to 50% of maximum 12 to 13 somewhat hard, 60% to 70% of maximum 14 to 16 hard, 75% to 95% of maximum 5. Activities can progress as tolerance is demonstrated. The appropriate initial intensity of training is 50% to 60% of WI, max or a rating of perceived exertion of 12 to 13 on a scale of 6 to 20. After safe activity levels have been established, duration is increased in 5-minute increments per week. Later, intensities can be increased as heart rate response to exercise decreases with conditioning. 6. tn patients with coronary artery disease, medical clearance is 166

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mandatory prior to exercise training classified according to risk. EXERCISE

and with

this, patients

can be

PROGRAMS

TYPES OF SUPERVISED PROGRAMS Medically Supervised Group (Moderate- to High-Risk Patients) These activity programs are needed to provide close medical supervision for individuals who are at high risk for a complication associated with vigorous physical activity.’ These individuals are largely from class D (see Appendix). These classes require careful medical supervision to ensure that the activity is well tolerated. A physician should be immediately available (in the facility), although the presence of a properly trained nurse in the exercise room is acceptable if the physician is not available. Training programs should be medically supervised until low risk of activity has been established. All individuals entering these pr’ograms should be screened as described in Table 7. The program should provide appropriate staff, space, equipment, and facilities (Table 8). Medically Supervised Group (Low-Risk Patients) Low-risk patients (classes B and C in Appendix) benefit from medically supervised programs because exercise can be conducted more safely and the “group dynamics” often help patients comply with other good health habits. If medical supervision by a physician cannot be provided, the person supervising should have successfully completed an AHA-sponsored course in advanced cardiac life support and be capable of administering emergency medication. Welltrained cardiovascular nurses usually meet these criteria. All individ-

TABLE 7. Screening Process for Medically Supervised Programs for High-Risk Patients* Consent of attending physician Stable clinical course Exercise test with current medications (for prescription1 Patient’s consent to accept responsibility for higher risk and to follow instructions for Imodi&ing risk Exercise prescription with electrocardiographic monitoring at beginning and for change in activity levels to ensure activity is well tolerated and to define desirable levels of (exercise ‘From Fletcher GF. Fmelicher VF Hartley LH, et al: Exercise standards: A statement sionals fmm the American Heart Association. Circularion 1990; 62:2286-2322. Used

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for health pmfesby pemission.

167

TABLE 8. Basic Requirements Patients*

for Medically Supervised Programs for Moderate- to High-Risk

Adequately ventilated and temperature-controlled space Capability to assess patients with blood pressure and electrocardiographic analysis. Electrocardiographic monitoring during initial sessions to ascertain desirable exercise levels. Supervision by either a nurse or physician in the exercise mom If a physician is not present, one must be immediately available iin the facility1 for consultation. Medically qualified staff lcompletion of an AHAt-sponsored advanced cardiac life support course [or the equivalent] and a minimum of two staff members present who are trained in cardiopulmonary resuscitationt Appropriate drugs and equipment (emergency medications, as outlined in the AHA’s 7%,~fbook ofAdvanced Cardiac Life Support) and cardioverter/ciefibrillatorr Standard orders for the nurse if physician is not immediately available Written procedures for the following: Identification

of conditions

Management

of problems that do not Inquire hospitalization

well-tolerated

arrhythmias

needed

and

to conduct

session

neuromuscular

such as acute,

injuries

Ruling out myocardial infarction and management of problems requiring hospitalization, including postresuscitation problems MIanagement of cardiac arrest, including procedure for immediate treatment transportation to hospital ‘From Fletcher GF, Fmelicher VF, Hartley LH, et al: Exercise standards. A statement siorlals fmm the American Heart Association. Circulafion 1990; 82.2286-2322. Used tAHA = American Heart Association.

and

for health pmfesby permission.

uals entering these programs should be screened as outlined in Table 9. The program should provide the same basic requirements as for high-risk patients as detailed in Table 8.

Records Cardiac rehabilitation instructors forms, records of progress in problem

should maintain evaluation areas, daily logs, and careful

TABLE 9. Screening Process for Medically Supervised Programs for Low-Risk Patients* Permission of patient’s personal physician, who judges patient to be either NYHAt functional Exercise

class test

without

1 or

2 severe

ischemic

changes

or

high-grade

ventricular

ectopy

Wilhngness to accept responsibility for higher risk and to follow instruction for modifying risk Exercise prescription with electrocardiographic monitoring at beginning and for change in activity levels to ensure activity is well tolerated and to define desirable levels of exercise heart rates ‘From Fletcher GF. Fmelicher \T, Hartley LH, et al: Exercise standards: A statement sirmats fiwm the American Heart Association. Circulation 1990: 82:2286-2322. tlsed tNYHA = New York Heart Association.

168

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for health pmfesbv permission.

Cardiol,

March 1992

documentation of complications and hospital charts.

in much

the same way as clinic

Regular EFercise Testing Exercise testing is important in all programs and should formed at regular intervals as discussed previously.

GlJlDELINES

FOR ELECTROCARDIOGRAPHIC

be per-

MONITORING

Various recommendations exist regarding the number of ECGmonitored sessions that are necessary and reasonable in an exercise training program. Some programs use as few as six sessions, with Pro$ ression in mode and intensity of the exercise during these periods ’ (Table 10). Others have used as many as 36 sessions of ECG monitoring. The fewest possible sessions should be used, and it is TABLE

10.

Six-Level Protocol for Monitolad -

Phase II Cardiac RehabilitationV Bicycle Ergometer

Level 1

5

6

Arm Ergometer 150 rpml 40% M M 100 Turns 2 Sets 45% M M 125 Turns 2 Sets 50% M M 125 Turns 2 sets 55% M M 15o'rurns 2 Sets 60% M M 150 Turns 2 Sets

Treadmill+

m-Leg5

Leg Only11

50% M M

50% MM 8 min

60% M M

60% M M 8 min

70% M M

70% M M 8 min

75% M M

75% M M 12 min

75% M M

75% MM 15 min

50% M M 50 rpm 8 rpm 55% M M 50 rpm 8 min 60% M M 60 ‘pm 8 min 60% MM 60 rpm 4 min No resistance 50 rpm 4 min Cool-down Do last

Repeat level 5

‘From Fletcher BJ, Thiel J, Fletcher GF: Phase II intensive monitored cardiac rehabilitation for corunay artery disease and coronary risk factors: A six-session protocol. Am J Cardid 19%; 56:751-i56. Used

b!/ permission. tPrescribed workloads should yield a 50% to 75% target heart rate range. Six minutes of warn-up flexibility and light calisthenics 110 repetitions per exercisel begin each exercise session. MM = maximal MET level achieved on exercise test; turns. revolutions. MU treadmill exercise consists of 1 minute of warm-up. 12 minutes of exercise. and 1 minute of rooldown Iwarm-up and cool-down = 1.2 mph at 0% grade1 SAir-Dyne; Schwinn, Chicago, Ill. /IBodyguard; Oglaend, Sadnes, Norway.

Curr Probl Cardiol, March 1992

169

recommended that the classification suggested in Table 11 be used as a guideline for the number of follow-ups required. Individuals who are class A (apparently healthy) do not require ECG-monitored sessions, as the general guidelines are adequate. Class B individuals should be monitored and supervised until they understand their desirable activity levels (usually 6 to 12 sessions). Class C and D individuals should be medically supervised with ECG monitoring until they understand the level of activity that is safe and the medical team determines that the exercise is well tolerated and effective. Usually 6 to 12 sessions or more are needed (see Appendix).

Monitored Cardiac Rehabilitation R/lonitoring sessions should ideally be performed with continuous ECG monitoring by either hardwired apparatus or telemetry. The session should be conducted by personnel who understand the exercise principles involved and have a basic knowledge of electrocardiography. The sessions should also be supervised by either a physician or a nurse trained in emergency CPR; this capability can be demonstrated by completion of an AHA-sponsored course in advanced cardiac life support. Standing orders for management of a complication should be immediately available. Monitored sessions should also include symptom assessment by the staff, systolic blood pressure recording, rating of perceived exertion, and instructions to patients about selection and proper use of exercise equipment. The ECG-monitored sessions should include sessions on adapting to different modes and progressions of exercise. The nonmonitored supervised phase of 12 weeks or longer involves progression as noted in Table 12.

TABLE 11. Guidelines for Electrocardiographic Activity Classificationt -

Monitoring

A-Apparently healthy B-Known stable CAD, low risk for vigorous exercise C-Known stable CAD, low risk for vigorous exercise but unable to self-regulate or to understand recommended activity levels D-Moderate to high risk for cardiac complications during exercise

in Exercise Training* Monitoring Not requited Monitored and supetvised lusually 6 to 12 sessionsl Monitored and supervised iusually 6 to 12 sessions or more Monitored and supewised sessions or more

lusuatly 6 to 12

‘From Fletcher GF, Fmelicher VF, Hartley LH. et al Exercise standards: A statement 101.health prufessionak fmm the American Heart Association. Circularion 1990; 82.2286-2322. llsed by permission tCA1) = coronary artery disease.

170

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TABLE 12. Phase I1 Nonmonitored

Exercise Training Pmtocol’t

‘Fmm Fletcher BJ, Lloyd A, Fletcher GF: Outpatient rehabilitatire training in patients with cardiovascular disease: Emohasis on training method. Heart Lune 1988: li.l99-205. Used bv oermissinn. t!ielected work ioads should yields a 75% to 85% targeT heart rate range. - 1 *MET values based on subject weighing 70 kg. SSelect work load on an individual basis with consideration given to previous activity level and patient’s cardiovascular status You may want to alternate various work loads. “15 Minutes of stretching and toning type exercises, approximately 15 to 20 repetitions per exercise. (Illsed indefinitely in long-term phase 111,nonsupenised mainrenance program.

EXERCISE TRAlNlNG

AT HOME AND IN THE WORKPlACE

These programs provide a reasonable alternative for patients who cannot attend a group-supervised program. For these types of nonmonitored programs, cardiac patients should ideally be designated as low risk and have had some initial training in a medically supervised program. For simplicity at home and at the worksite, the exercise training protocol in Table 13 incorporates only dUynamic activities of walking/jogging and bicycling. Swimming, outdoor cycling, a.nd rowing may be substituted if carefull,y done. Each exercise session should be preceded by 5 to 20 minutes of warm-up calisthenics.30 The dynamic exercise prescription should increase on a reguCurr

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171

TABLE

13.

Exercise

Training

Protocol’t

Fletcher BJ, Griffin PA, Lloyd A, et al: Cardiac rehabilitation in the workplace, c”rrz”t concepts and methods. American Associatron cfOcc~rpational Health Nurst:s Journal 19YO: 3R:WZ. L&d by permission. tERG0 = stationaT bicycle ergometer: rxp = repetitions; MET = metabolic equivalent; 1 MIX = 3.5 nd/kg/mgm of oxygen consumed. /I = MET Level, in parentheses; II = workload, in brarkrts: kp = kilipond; W = watt *MET values based on subject weighing 70 kg SSrlect workload on a” individual basis with consideration given to prrvious activity level and client’s can~iovascular status. You may want to alternate various workloads. Selected workloads should .yield a 70% to 85% target heart rate range. “5-20 minutes of stretching and toning type exercises, approximately 15 tu 20 repetitions per exercise IlLlsed indefinitely in long term maintenance program ** = Air-Dyne. Chicago. ‘From

lar basis in duration and intensity (see Table 13, Levels 1 through 6) until persons achieve their maintenance level. Frequency of the exercise prescription remains constant at 3 to 5 times per week, depending on the individual. In general, activity is increased to incorporate 45 to 60 minutes of dynamic exercise 3 to 5 times per week. Generally this consists of progressing to a total of 3 miles of either walking or slow, “careful” jogging, or a combination, and 15 minutes on a stationary cycle. Some may prefer to cycle more and walk/jog less, or vice versa. Selection of the specific intensity for each level (see Table 131 of the exercise prescription is best achieved if one knows the MET level individuals achieved on their exercise test. ‘The prescribed exercise or activity level should be 60% to 85% of the MET level achieved on the exercise test. For example, if an individual achieved a MET level 172

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of 6.0 on the exercise test, this person’s exercise prescription should begin at 3.6 METS (60% of 6 METS). According to Table 13, Level 1, this would be walking slightly less’ than a 16 minute per mile pace. The activity level on a leg-only stationary bicycle would be a speed of 60 ‘pm and resistance of slightly less than 1, or if using an arm-leg bicycle, a workload of ?4 or .75 should be achieved. Prescribing the proper MET level should result in persons achieving their target heart rate range. If not, an increase or decrease in the intensity may be needed to achieve the target heart rate range. The goal is to have the individual achieve and maintain a heart rate r,ange at 70% to 85% of that reached on the exercise test. When prescribing the home or workplace exercise training prog,ram, all six levels should be prescribed initially or at one time. This can be altered if the individuals are overachieving or underachieving their target heart rate range. Each individual should remain at each level for approximately six exercise sessions or 2 weeks before progressing to the next level. When the individual achieves Level 6, the exercise routine should be maintained. The use of transtelephonic ECG monitoring at home has been suggested as a substitute for outpatient visits to the clinic.“l’ 32 Such programs have the disadvantage of lacking immediately available emergency medical care, but the advantage of no required clinic visit. The equipment is also not generally available, but these programs would be particularly useful in following up high-risk cases in which clinics are not readily available. IJnmonitored Home Programs In the first 1 to 2 weeks after discharge from the hospital after myocardial infarction or other cardiac events, individuals may walk at a slow, regular pace with increasing duration, starting with loIminute periods and working up to 1 hour. Such activity need not be isupervised but should be maintained at low intensity.

WES

OF EXERCISE

Dynamic vs Isometric Exercise The physiologic response to increasing dynamic (isotonic) exercise in young to middle-aged persons is an increase in heart rate with an associated increase in stroke volume. In elderly patients, the increase in heart rate predominates, with little increase in stroke volume. Systolic blood pressure increases progressively with maintenance of, or slight decrease in, diastolic blood pressure. Improved oxygen extraction, aided by redistribution of blood flow to working muscles, increases the systemic arteriovenous oxygen difference. The increase in heart rate is modest with isometric exercise, is not Curr

Probl

Car&d,

March

1992

173

r&ted to the intensity of the effort, and the increase in cardiac output is slight. There may be an increase in systolic blood pressure with high-intensity isometric activity that may provoke angina, left ventricle dysfunction, and/or arrhythmias and this is the basis for limiting isometric activity in rehabilitation of patients with recent infarction. Because a pressure load causes little improvement in cardiovascular function, isolated isometric training has not been a major component of rehabilitative physical activity. Combined isotonic and isometric training, however, may produce a substantial training effect in appropriately selected coronary patients,33 and the enhanced muscle strength from isometric training often aids in dynamic endurance exercise. However, health professionals should keep in mind that wall motion abnormalities may be aggravated by isometric activity even in exercise-trained coronary patients.“’

Arm Work vs Leg Work and Training Both arm and leg exercise should be included in a training regiAfter leg men,35 as their effects are only modestly interchangeable. training, the heart rate and blood pressure responses to leg work decrease, but there is a lesser improvement in the responses to arm work. After arm training, the predominant decreases in heart rate and blood pressure response occur with arm work. In one study,36 improvement in exercise performance with the untrained limb was 50Y0 to 75% of that with the trained limb, suggesting that half of the increase in trained-limb performance is caused by generalized training effect and the other half reflects, predominantly, an improved oxygen extraction by trained skeletal muscle. A work load approximating 50% of that used for leg training is appropriate for arm trainoxygen uptake, arm work evokes a higher w+y5 At a comparable heart rate and systolic blood pressure response than does leg exercise. Because most occupational and recreational activities entail both arm and leg work and often involve predominantly arm work, spec:ific arm muscle exercises must be included in rehabilitative exercise training to improve physical performance. One review recently specifically addressed myocardial and aerobic requirements for upper body exercising. This has become quite important in patients with paraplegia, amputations, neurologic, vascular, and certain other orthopedic and musculoskeletal problems of the lower extremities. In this setting, particularly with centers where general rehabilitation programs are active, upper extremity activity is most important in patients with associated cardiovascular disease. In addition, upper extremity activity is important to consider in those whose occupational and work activity is predominantly done by arm activity. This is true in many instances because of the nature 174

Cwr

Prohl

Cardiol,

March 1992

of industrial occupational and vocational activity, which is mostly arm work.37 In addition, data are available on weight training to improve strength and maximal power output in coronary artery disease.3n In such studies, it is demonstrated that dynamic weight training, in clombination with aerobic dynamic exercise, is a more effective method in increasing muscle strength and maximal power output in conditioned patients with coronary artery disease than aerobic endurance training alone. This is important in the overall care of the patient in cardiac rehabilitation programs, and certainly adds variety for those who have interest in weight training because of previous athletic interests or current interests in a variety of training modalities. ) D. McCall: There is no doubt that exercise training results in considerable physical improvement in many patients following a myocardial infarction. Others, however, do not show this improvement and some may even demonstrate adverse effects (Prog Cardiovasc Disease 29381, 1986). Furthermore, it has recently been demonstrated (J Am Co11 Cardiol 15-974, 19901 that only about 59% of patients will so benefit. On this basis, it should be clear, that such an approach to cardiac rehabilitation must be determined on an individual basis rather than as a general prescription. It has also been shown U Am Co11 Cardiol 15:974, 19901 that it is possible to identify those likely to benefit Iiom exercise training by clinical data, data derived from exercise testing and the psychosocial profile of the individual patient.

BLOOD

LIPID

CONTROL

Of all coronary risk factors, the most important for modification in the secondary prevention and control of atherosclerotic cardiovascular disease is management of abnormal blood lipid levels. Substantial and convincing data on the importance of controlling elevated blood cholesterol after a cardiac event have been published fsince the mid-1960s.3g-47 Table 14 lists these supportive studies, and ,several others are now in progress. In managing abnormal blood lipid levels in the cardiac rehabilitative setting (as in other settings), the lipoprotein profile must be considered. The lipid profile-total cholesterol (TC), triglyceride (TGI, high density lipoproteins (HDLs), and calculated low density lipoproteins (LDLs)-should ideally be done. For TC and HDL measurements, the subject need not be fasting, but total fasting (2 hours) is required for TG measurements. The following formula

used for calculating TC -

Curr

HDL

Probl

I2 is

LDL levels:

- TG + 5 = LDL

Cardiol,

March

19%

175

TABLE 14. Clinical Trials Supporting

Benefits of Controlling

Abnormal

Blood Lipids

Oslo Study (LerenJ3Y Western Electric Studya Multiple Risk Factor Intervention Trial” Lipid Research Clinics Coronary Primary Prevention Trial”! Helsinki Heart Study43 Comnaly Drug Project* National Heart, Lung and Blood Institute Type II Stud-v” Colestipol-Niacin Therapy Study on Coronary Athemsclemsis B-ypass Grafts4” The Cholesterol Lowering Athemsclemsis Study”’

and Coronary Venous

This’ method of determining LDL levels is used in most laboratories, although direct measurement of LDL levels is available in certain research centers. A few special considerations are important in evaluating blood lipid levels, especially in secondary prevention. The non-HDL cholesterol level should be evaluated because TC includes the HDL component. The TC/HDL ratio is commonly used in patient evaluation, but the absolute values should also be considered independently. Determining the apolipoprotein values adds expense to the test, but these may be more specific in detecting and further defining underlying problems. Higher apolipoprotein A levels are consistent with a “protective” lipid effect; higher apolipoprotein B levels constitute a strong coronary risk marker. Assessment of HDL subtypes is also important. HDL, was once thought to be the only HDL that conferred a coronary protective effect; however, data from the Physicians Health Study4’ suggest that both HDL, and HDL, are beneficial if normal or elevated. HDL,, is metabolized to HDL,, so the individual subtypes may not be as important as once believed. Lastl,y, the very high HDLs deserve special attention. Preliminary observations in the program at Emory University indicate that such “very high” HDLs (2 80 mg/dl) are usually seen in healthy women and, therefore, may indicate a cardioprotective effect in this population .‘19 Lastly, a physical examination is important in determining whether the hypercholesterolemia is primary or secondary. Tuberous tendon and palmar xanthomas are associated with long-standing abnormal blood lipid levels. Xanthelasma may or may not be associated with dyslipidemia. In addition, the venous blood sample may be suggestive of abnormal lipids when the clotted serum is turbid.

176

Corr

Probl

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March 1992

L~EFINITION

OF LIPID CONTROL

A desirable mean blood TC level is 160 mg/dl; however, the current average mean blood TC level in this country is about 210 mg/dl, and these levels (or higher1 are frequently seen during cardiac rehabilitation. Based on data from the National Cholesterol Education Program (NCEP)” and the AHA, guidelines for controlling blood TC levels have been issued for health professionals. As such, the desirable TC level is 200 mg/dl or less, borderline high is 200 to 239 mg/dl, and .240 mg/dl or greater is considered high. Categories of management are usually based on these strata, and levels attained well below the 200 level are necessary in secondary prevention. Patients with high TC levels should also be evaluated for any condition that might cause secondary high TC levels, such as cliabetes mellitus, hypothyroidism, nephrotic syndrome, and use of certain drugs. MANAGEMENT

STRATEGIES

There are three basic phases that are used in managing patients with elevated blood lipid levels and have been effective in the Emory 1Jniversity cardiac rehabilitation program. These are based on NCEP and AHA guidelines that are widely accepted. Phase 1 is essentially a general improvement in health habits and involves a lifestyle change. The components of phase 1 are nutrition guidelines, weight loss, and physical activity. Phase 2 is an extension of phase 1, with the possible addition of fiber supplements and at times nicotinic acid. Phase 3 is an extension of phases 1 and 2, and includes lipid-lowering drugs, singly or in combination. It is believed that, regardless of the severity of the blood lipid abnormality, phase 1 should be instituted initially in most subjects for 4 to 6 weeks, at which time blood lipid levels should be reevaluated. The rationale for initiating management with phase 1 is clear when the mechanisms of the dietary effect on cholesterol are under#stood: 81Dietary cholesterol itself suppresses the synthesis of LDL receptors, primarily in the liver but also at peripheral sites. l Saturated fats, on the contrary, reduce the activity of the existing LDL receptors. . Obesity or excess weight stimulates overproduction of lipoproteins. DIETARY CONTROL It is important that the patient understand the major sources of dietary lipids. The primary sources of dietary cholesterol are eggs, Curr

Probl

Cardiol,

March

1992

177

dairy products, organ meats, and certain red meats. The chief sources of saturated fats are dairy products and eggs, but plant and tropical oils such as coconut and palm kernel oil are also high in saturated fats, although they do not contain cholesterol. The AHA guidelines, which are very similar to those of the NCEP, are most widely used for low cholesterol and low saturated fat diets. The characteristics of cholesterol-lowering diets are shown in Table 15. The average American currently consumes about 400 mg of cholesterol daily. The step 1 AHA diet recommends less than 300 mg per day of cholesterol (a large egg yolk contains about 250 mg). Step 2 limits daily cholesterol to 200 mg, and restricting saturated fats is also important, as outlined in Table 16. The experienced nutritionist’s role is vital in the cardiac rehabilitative setting in formulating dietary guidelines based on dietary assessment and in educating patients about how to buy foods and interpret labels. Benefits from dietary changes can be seen as early as 4 to 6 weeks afterward. Encouragement and cooperation from a spouse or significant other are important to the success of lifestyle changes, and often family involvement in the dietary change elicits a rewarding result. EXERCISE INTERVENTION Exercise, in conjunction with dietary changes, is of considerable importance in controlling lipids. Weight loss and reduced body fat are associated with decreases in TC and increases in HDL.” In addition, more recent data support benefits of physical activity for those at risk of hypertension and noninsulin dependent diabetes mellitus.52 Exercise in a phase 1 setting can be low in intensity, but should be regular, on nonconsecutive days, and of sufficient duration to impose a training effect as is done routinely in cardiac rehabilitation programs. The phase 1 approach to blood lipid control is typified by the following example. 55-.year-old man with two previous myocardial infarctions and occasional short periods of ventricular tachycardia on treatment was referred to a cardiac rehabilitation program. His initial TC level was 258 mg/dl, and HDL

A

TABLE

15.

Characteristics Constl&uent

of American Heart Association Cholesterol-bwering Current American Diet

350 to 500 Cholesterol (mg/dayJ Saturated fatty acids 14% to 18% (percent of calories) ‘AHA =. American Heart Association 178

Diets

Step 1 AHA* Diet

Step 2 AHA Diet

i 300

i 200