Attenuation of Exercise-Induced ST Depression During Combined Isometric and Dynamic Exercise in Coronary Artery Disease Kim Bertagnoli, MS, Peter Hanson, MD, and Ann Ward, PhD ST-segment depressIon was measured during submaximal dynamic (treadmill) and combined isometric-dynamic (isodynamic) exercise at comparable rate-pressure products in 11 patients (mean age 63 years) with stable coronary artery disease who were participating in an exercise training program. Each patient completed 3 separate trials. Trial 1 (baseline) was a submaximal treadmill exercise test to determine the threshold heart rate-systolic Mood pressure (rate-pressure product) for ST-segment depression (L 1.0 mm). During trials 2 and 3, patients performed (in random order) dynamic treadmill exercise and isodynamic exercise (treadmill walking 1.5 to 2.0 mph carrying 15 to 25 kg) until threshold rate-pressure product was achieved. During trial 1, each patient showed signitlcant ST depression (mean 1.7 mm) at target rate-pressure product (mean 18,200). Subsequent dynamic exercise trials 2 and 3 showed similar mean ST depression (1 .J mm) and rate-pressure product (18,000). During isodynamic exercise trials 2 and 3, subjects showed only minimal ST depression (mean 0.4 mm) at a rate-pressure product similar to dynamic exercise (mean 18,560). Heart rates were signlftcantly lower (-lO/min) and systolic (+20 mm Hg) and diastolic (+2S mm Hg) pressure was higher during isodynamic exercise (p 50% obstructed N = nitrates: RPP = heart rate X systohc blood pressure;
CB
N N N D
CB F calcium antagonist; D = dl1 = mrd: 4 i = moderate. + = yes; 0
metabolic rate; 3.5 ml Oz/kg/min). Each subject con- ment changes L 1.O mm. The speed of the treadmill was sistently demonstrated a minimum of 1.0 mm of ST- set at a brisk walking pace (3.0 to 3.5 mph) and the segment depression at submaximal exercise intensities grade increased every 2 minutes producing +l MET within a range of &l MET of their prescribed training increases in exercise intensity.13 Blood pressure was level. None of the subjects showed ECG changes of left measured at each minute and a 1Zlead electrocardioventricular hypertrophy or ST-segment depression at gram was taken during the second minute of each stage rest, and none was taking digoxin. All subjects re- and at the test endpoint. The baseline treadmill test was mained on prescribed medications during the study. terminated when 1.0 mm of ST depression was obProtocol and measurements: Each subject was eval- served. The rate-pressure product was then calculated uated during 3 separate trials with at least 1 day of rest from heart rate and systolic blood pressure measured between each trial. During each session, heart rate and during the last minute of the test. This value was used ECG changes were monitored using a Burdick 3-chan- as a target rate-pressure product for comparison of dynel, 12-lead ECG recorder system. Blood pressure was namic and isodynamic exercise. determined at rest and during exercise by auscultation Dynamic and isodynamic exercise tests were perusing a mercury manometer and modified stethoscope formed in each of 2 subsequent trials (2 and 3). The with a standard anesthesia diaphragm held firmly over sequence of the dynamic and isodynamic exercise sesthe brachial artery by Velcro strap. Previous studies us- sions was randomly selected by each subject to avoid ing this method have shown an excellent correlation of order of performance bias. systolic pressure (r = 0.95) compared to simultaneous Dynamic exercise began with a 2-minute warmup brachial intraarterial pressure recordings.12 stage at 0% followed by 3-minute stages at the same During trial 1 (baseline), each subject performed a treadmill speed and grade attained during the trial 1 submaximal treadmill exercise test to determine the exercise test. Isodynamic exercise was performed by rate-pressure product threshold for ischemic ST-seg- walking on the treadmill at 1.5 to 2.0 mph (mean speed
q
250 225
Heart rate 0 Blood pressure
200 175
FIGURE 1. Heart rate and blood wponsestodynamkmdisodynamk
t
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exedse.Trid1Isbadinedynamii exercke.Triak2and3aredyniwnk and isodynamic exercise rateqreuure product.
at eqdvalent
Values are mean
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CB
N N N D
CB F calcium antagonist; D = dl1 = mrd: 4 i = moderate. + = yes; 0
metabolic rate; 3.5 ml Oz/kg/min). Each subject con- ment changes L 1.O mm. The speed of the treadmill was sistently demonstrated a minimum of 1.0 mm of ST- set at a brisk walking pace (3.0 to 3.5 mph) and the segment depression at submaximal exercise intensities grade increased every 2 minutes producing +l MET within a range of &l MET of their prescribed training increases in exercise intensity.13 Blood pressure was level. None of the subjects showed ECG changes of left measured at each minute and a 1Zlead electrocardioventricular hypertrophy or ST-segment depression at gram was taken during the second minute of each stage rest, and none was taking digoxin. All subjects re- and at the test endpoint. The baseline treadmill test was mained on prescribed medications during the study. terminated when 1.0 mm of ST depression was obProtocol and measurements: Each subject was eval- served. The rate-pressure product was then calculated uated during 3 separate trials with at least 1 day of rest from heart rate and systolic blood pressure measured between each trial. During each session, heart rate and during the last minute of the test. This value was used ECG changes were monitored using a Burdick 3-chan- as a target rate-pressure product for comparison of dynel, 12-lead ECG recorder system. Blood pressure was namic and isodynamic exercise. determined at rest and during exercise by auscultation Dynamic and isodynamic exercise tests were perusing a mercury manometer and modified stethoscope formed in each of 2 subsequent trials (2 and 3). The with a standard anesthesia diaphragm held firmly over sequence of the dynamic and isodynamic exercise sesthe brachial artery by Velcro strap. Previous studies us- sions was randomly selected by each subject to avoid ing this method have shown an excellent correlation of order of performance bias. systolic pressure (r = 0.95) compared to simultaneous Dynamic exercise began with a 2-minute warmup brachial intraarterial pressure recordings.12 stage at 0% followed by 3-minute stages at the same During trial 1 (baseline), each subject performed a treadmill speed and grade attained during the trial 1 submaximal treadmill exercise test to determine the exercise test. Isodynamic exercise was performed by rate-pressure product threshold for ischemic ST-seg- walking on the treadmill at 1.5 to 2.0 mph (mean speed
q
250 225
Heart rate 0 Blood pressure
200 175
FIGURE 1. Heart rate and blood wponsestodynamkmdisodynamk
t
preuure
exedse.Trid1Isbadinedynamii exercke.Triak2and3aredyniwnk and isodynamic exercise rateqreuure product.
at eqdvalent
Values are mean
flsta~de!*.*p
