BY. J. Dis.

EXERCISE D. G. GILMOUR,” Departments

of Medicine

TESTS BEFORE AND AFTER VALVE REPLACEMENT

Chest

(1976)

70, 185

HEART

S. G. SPIRO,~ M. J. RAPHAEL AND S. FREEDMANI and

Radiology,

Royal

Postgraduate

Medical

School,

London

Summary A simple progressive exercise test was performed before and after operation on five subjects undergoing mitral valve replacement and on five subjects undergoing aortic valve replacement. The responses of heart rate and ventilation were related to work rate (kilopond metres/min). The patients were also assessed clinically by the New York Heart Association grading and radiologically before each exercise test. The clinical grading was shown to be a poor guide to observed exercise tolerance, as the improvement noted in symptoms was not matched by the objective measurement of working capacity. Only two patients had normal exercise tolerance after surgery, although six of the ten patients claimed that they had no exertional dyspnoea after operation. The changes in simple ventilatory function tests before and after operation were generally small. We suggest that measurements of exercise tolerance before and after operation should be an essential part of heart valve replacement surgery.

INTRODUCTION

The results of surgical replacement of the mitral and aortic valve has been justified (Graham et al. 1971; Gonzalez-Lavin et al. 1972; Somerville et al. 1972). Assessment of the results of surgery has been based on symptoms (Fleming et al. 1969; GonzalezLavin et al. 1972; Oh et al. 1973) or on haemodynamic studies at rest (Graham et al. 1971; Somerville et al. 1972). Earlier work on patients undergoing mitral valvotomy indicated that there was often a discrepancy between assessment by symptoms and assessment by measurement (Wade et al. 1954; Bergy & Bruce 1955; Holmgren et al. 1958; Chapman et al. 1960). There is a wide interest in exercise testing of patients with coronary artery disease, both before and after surgery. There have, however, been no studies of the effects of mitral valve replacement which have included pre- and postoperative measurements of exercise tolerance, even though exertional dyspnoea is commonly an indication for surgery. In this preliminary study we have measured the responses of patients to a simple progressive exercise test before and after replacement of either the mitral or the aortic valve.

+ Present address: Matthew Thornton Medical Center, 591 W. Hollis Street, Nashua, New Hampshire 03060, USA. T Present address: Division of Respiratory Medicine KM-1 2, University of Washington, Seattle, Washington 98195, USA. 1 Present address: Chace Wing, Enfield District Hospital, Enfield, Middlesex.

186

D. G. Gilmour, S. G. Spiro, M. j? Raphael and S. Freedman Patients and Methods

We studied patients with disease of either the mitral or the aortic valve, but not those who had disease of more than one valve. We chose patients who were not too incapacitated to exercise and studied them one to two weeks before operation. Two patients were studied twice before operation and the remainder once. Twenty-two patients were studied initially but only 10 were available for postoperative study, of whom five had had mitral valve replacement and five aortic. Some anthropometric and clinical details of these 10 patients are given in Table I. Of the remaining 12 patients,

TableI. Case

Sex

Age

M

36

2

F

57

3

F

60

4 5 6

F M M

27 35 22

7

M

46

8

M

59

9 10

F M

44 36

lesion

given

details

of 10 patients

Rheumatic aortic stenosis (aortic regurgitation) Rheumatic aortic stenosis (aortic regurgitation) Rheumatic aortic stenosis (aortic regurgitation) Rheumatic aortic regurgitation ?Congenital aortic regurgitation Congenital mitral regurgitation ventricular septal defect Rheumatic mitral stenosis (mitral regurgitation) Rheumatic mitral stenosis (mitral regurgitation) Rheumatic mitral stenosis Rheumatic mitral stenosis (mitral regurgitation)

first,

Main symptoms before operation

Diagnosis*

(years)

1

* Dominant

Clinical

secondary

lesions

Angina

and

pectoris

Exertional

dyspnoea

Exertional

dyspnoea

Fatigue Exertional Exertional

on exertion dyspnoea dyspnoea

Exertional

dyspnoea

Exertional

dyspnoea

Exertional Exertional (chronic bronchitis)

dyspnoea dyspnoea

in parenthesis.

three died after operation, four were judged unsuitable for surgery and five were unavailable for follow-up either because they refused-further tests (three patients) or lived a long way from the hospital and were being followed up locally. The operations were performed by Mr W. P. Cleland or Professor H. H. Bentall. The 10 postoperative studies were carried out 6 to 12 months after surgery. Five of the patients were also studied one to three months after surgery. All five patients with mitral valve disease and the one patient with atria1 fibrillation in addition to aortic valve disease were taking digoxin. The doses were similar before and after operation. There were some differences in the diuretic regimens before and after operation. All the patients agreed to perform the exercise test after it had been explained that it did not form part of the normal investigation or management of their disease. During the standardized progressive exercise test we measured pulmonary ventilation and heart rate. The test was performed on an electrically braked cycle ergometer (Elema) fitted with a tachometer which displayed the pedalling rate in revolutions per minute. The patients breathed through a valve with 60 ml dead space, inspired ventilation being measured with a dry gas meter (Parkinson-Cowan Limited), modified to give an electrical output which was continuously recorded on a Mingograf 81 chart recorder (Elema). ECG was recorded continuously, using one lead placed over the heart and one on the back of the chest with the indifferent electrode on the right arm. The ECG waveform was also displayed continuously on an oscilloscope with a large screen. When the patient was comfortably seated on the bicycle and was familiar with the mouthpiece

Exercise Tests and Heart Valve Replacement

187

and noseclip, the load on the ergometer was set at 100 kpm/min (equivalent to 16.7 W) and the patient instructed to pedal at 45-75 rpm, watching the tachometer in order to keep the rate as constant as possible. The load was increased by 100 kpm/min at the end of each minute until the patient was forced to stop by breathlessness, general fatigue, angina pectoris or other symptoms. The test was stopped by us if ventricular ectopic beats appeared on the ECG display. Forced expired volume in 1 set (FEVr) and vital capacity (VC) were measured using a dry spirometer (Garw Ltd). Clinical assessment of the patients was carried out before and after operation during routine visits to a clinic by a physician who was unaware of any of the results obtained during exercise. He graded the patients O-IV, according to their incapacity, using the New York Heart Association classification (1953). Haemodynamic data were obtained during routine preoperative cardiac catheterization or during the operation itself, before and after replacement of the defective valve. Chest radiographs were assessed by an author (M.J.R.) who was completely unfamiliar with the patients or with any of the other data. Films were selected (by another author) which were taken as close as possible in time to the day on which the exercise test was performed. In most cases, films taken on the same day were available. The films were all read at one session, after the completion of all the other studies. Films from each patient before and after operation were compared and the following assessed : maximum heart diameter (on PA review), upper lobe venous congestion (graded 0 to + + +), and the presence of septal lines and pulmonary oedema.

Table

Case

II.

Pre-

Haemodynamic data*

Prosthetic valve

6 7 8 9 10

postoperative

clinical

and

physiological

Maximum work load (kpmlmin)

data

FEVI ( y0 predicted)

VC predicted

Clinical

grade

(%)

Before

After

Before

After

Before

After

Before

After

III III

I 0

300 400 200 400 700

800 600 400 500 900

93 101 84 88 -

90 84 70 92 -

102 136 66 88 -

102 114 79 97 -

600 500 500 200 600

800 600 600 400 500

72 62 55 82 36

74 69 55 77 12

80 93 76 110 72

88 90 57 107 38

resting Before

No. 11 Starr No. 9 Starr No. 9 Starr Homograft No. 12 Starr

and

110

No. 3 Starr No. 4 Starr No. 4 Starr No. 3 Starr Homograft

After 0

80

0

40 0 44

0 0 12

III II II

1-t 0 0

30 28 26 33

19 22 14 26

II III III III

0 Of It Of

32

12

III

11t

* Recorded as gradient across aortic valve (mmHg) in cases 1-5; preoperative data obtained during cardiac catheterization and postoperative at the time of operation. Recorded as mean left atria1 pressure (mmHg) in Cases 6-10; both preoperative and postoperative figures obtained during operation. t Atria1 fibrillation before and after operation.

RESULTS Details

of clinical

grade,

maximum

tolerable

work

load,

pulmonary

function

dynamic data before and after operation are given in Table II. Maximum clinical grade are compared in Fig. 1.

and

haemo-

work load and

188

D. G. G&now,

S. G. Spiro, M. J Raphael and S. Freedman

These data show, first, that the NYHA clinical grade is a poor guide to exercise tolerance, since at any one grade there are big differences in measured maximum work loads. Secondly, the maximum tolerable work load became normal after surgery in only two patients (one man 900 kpm/min and one woman 600 kpm/min). Thirdly, although all patients claimed marked subjective relief in the severity of their exertional dyspnoea, this was accompanied, in most cases, by only a modest improvement in maximum work-load. Thus, though six of the 10 patients claimed that they had no exertional dyspnoea after operation only two of these achieved a normal maximum work-load, while one patient who claimed an improvement in subjective grading, showed a diminution in measured exercise tolerance. Fourthly, with one exception, there was no suggestion that the extent of the subjective or objective improvement after operation was in any way related to the degree of incapacity before operation. The 900

r

.z -2

700

s 600 2 ,o A

500 800

I

M 0 A

MITRAL AORTIC

1

I CLINICAL

Fig. 1. The

relation

between

clinical

grade

F . ,

0

GRADE

(NYHA)

and

maximum

work-load

before

and

after

operation

exception was one patient (Case 1) with aortic stenosis whose exercise tolerance was limited before operation by angina and after operation by dyspnoea. Heart rates and pulmonary ventilation during the progressive exercise tests are given in Figs 2-5. Data from both postoperative studies are included in these figures. Each individual chart also includes the normal range ( + 1 SD) for men or women from data obtained in the Hammersmith Hospital laboratories (unpublished observations). All exercise studies before and after operation were limited by the patient stopping and complaining both of dyspnoea and general fatigue, particularly aching legs. One subject was limited before operation by angina and one after operation only by dyspnoea. No arrythmias were seen during any exercise test and no test was stopped prematurely by the observer. In the patients who had aortic valve replacement heart rates were lower after operation in two and higher in three (Fig. 4). After mitral valve replacement, heart rates were

Exercise Tests and Heart Valve Replacement

200

189

6cf

-

Preoperative

----PostoperatIve

Work

load (kpm,‘vm

1

Fig. 2. Heart rate response to progressive exercise before and after operation in patients with mitral valve disease. The stippled band represents the normal range ( f 1 SD) for normal subjects from this laboratory. The figures ‘1’ and ‘2’ refer to the first and second postoperative studies

200 Work

Fig. 3. Pre- and postoperative ventilatory valve disease. Normal range and symbols

400 load

response

600

(kpm/m,n

to

000

0

200

400

600

800

)

progressive exercise in patients with mitral

as in Fig. 2

lower in two patients, higher in two and unchanged in one (Fig. 2). The interpretation of these data is complicated by the presence of atria1 fibrillation in five of the ten patients, as further discussed below, but they do show that on the whole patients did not stop

190

D. G. Gilmour, S. G. Spiro, M. J. Raphael and S. Freedman

180

t

200

400

600

800

200

400

600

800

200

400

600

800

200

400

600

800

SO200

400

80Work

load

( kpm / rmn )

Fig. 4. Pre- and postoperative heart rate response to progressive valve disease. Normal range and symbols as &I Fig. 2 - -

60

tg-r

..:,:..

200

400

600

exercise in patients

aortic

with

2

I 200

800

z

I 200 Work

Fig. 5. Pre- and postoperative ventilatory vaIve disease. Normal range and symbols

I 400 load

I 600

I 400

I 600

I 800

I 800

(kpm/mln)

response to progressive as in Fig. 2

exercise in patients

with aortic

exercising when their heart rates reached a certain value, but that in most of them increased maximum work-load after operation was accompanied by a higher heart rate. Pulmonary ventilation during progressive exercise (Figs 3 and 5) was less after surgery

191

Exercise Tests and Heart Valve Replacement

in six patients, unchanged in three and greater in one. Again, increased maximum work-load was usually accompanied by an increased ventilation. The changes in the ventilatory response to exercise cannot be attributed to changes in ventilatory function (FEVr and VC) which were generally small, except in Case 10 whose lower exercise ventilation was probably due to his lower ventilatory capacity. Radiographic changes before and after operation are summarized in Table III. None of the patients had evidence of pulmonary oedema after operation but upper lobe pulmonary congestion persisted in five of the eight whose films were read. Heart size was not greatly reduced in any of the patients and in one (Case 10) was increased. Table

Case

1

2 3 5 6 7 8 9 10

Maximum diameter

cardiac (cm)

III.

Radiological

changes

Upper lobe venous congestion

Before

After

Before

15.5 14.0 16.5 17.0 18.0 19.0 18.0 20.0 16.5

14.0 14.0 15.5 15.0 17.5 19.0 18.0 19.0 18.0

0 0 ++ + ++ ++ +++ ++

After

Sep tal lines

Before

After

Pulmonary Before

oedema After

0 0 + 0 + + ++ +++

DISCUSSION Our results, based on a standard, simple progressive exercise test, showed that symptomatic improvement was not usually matched by the objective measurement of exercise tolerance. The question therefore arises whether our patients were comparable with those reported by previous authors in their response to valve replacement. We can compare them in three ways: symptomatic improvement, radiological changes and haemodynamic changes. All but one of our patients improved by two or more NYHA grades. This is similar to the results in larger series. Thus, Graham et al. (1971) reported that 100 out of 107 patients improved from grade III or IV to grade I or II, and Oh et al. (1973) found that 72% had improved by one or more grades. Gonzalez-Lavin et al. (1972) stated that 80% of 259 patients who underwent aortic valve replacement were symptom-free at periods ranging from 18 months to seven years after operating. Fleming et al. (1969) reported a ‘striking improvement’ in symptoms and that most of their surviving patients were leading a normal life. Previous reports which included an exercise test in the assessment of subjects undergoing heart valve surgery have been confined to those undergoing aortic valve replacement. Bjork and Cullhed (1967) measured an increased exercise capacity in only five of 18 subjects undergoing successful surgery. Other studies have used their own standards of assessment such as the ‘exercise factor’ (Andersen et al. 1971) in evaluating the

192

D. G. Gilmow, S. G. Spiro, M. 7. Raphael and 5’. Freedman

benefits of surgery. Andersen et al. (1971) showed there was no objective evidence of improvement in patients of NYHA grade III or IV who underwent surgery that was considered technically less than satisfactory. In those subjects undergoing successful operations there was in general an increased capacity to exercise; their preoperative clinical grading was not, however, stated. The radiological changes in our patients were not particularly impressive. Half of them had a decrease in heart size diameter of 1 cm or less, although there was a general tendency for vascular markings to decrease and for oedema to disappear. Somerville et al. (1972) found that 37 of their 43 patients showed a significant decrease in heart size after aortic valve replacement and those of our patients who underwent this operation did show bigger falls in cardiac diameter than those with mitral disease, in agreement with previous findings. Haemodynamic data in our subjects were obtained a few days before operation and repeated during operation. They were comparable with those of Graham et al. (1971), obtained before and after operation at rest. In each of our cases of mitral valve disease an immediate fall in pulmonary capillary or wedge pressure was recorded which would appear consistent with a good operative result, while the gradient across the aortic valve was abolished in all our patients undergoing aortic valve replacement. On the basis of these three criteria our patients appear comparable with those previously reported. The measurement of progressive exercise tolerance might have been affected by factors other than physiological ones. An improvement might have occurred on repeated testing because patients became more familiar with the surroundings and apparatus, but if this did happen, it would add emphasis to our finding of only modest improvements in measured exercise tolerance. It is also possible that the patients were trying harder after operation, but the same argument would then apply. Most of the patients stopped the exercise test because of dyspnoea and, with the exception of patients Cases 1 and 10, the limiting symptom was generally the same before and after operation. Nine of our ten patients improved subjectively to gain NYHA grade 1 or 0. Their progressive exercise tolerances were, however, much less than expected. Our findings resemble those of Bergy and Bruce (1955) who assessed the results of mitral valvotomy. They found that 29 of their 31 patients reported subjective improvement, but that only 16 had improvement in measured indices of physical fitness. In a study of exercise tolerance in patients with valvular and other types of heart disease, Patterson et al. (1972) found a rather poor correlation between the NYHA grades and peak oxygen consumption. The correlation was especially poor in NYHA grade I patients, in whom there was a very wide scatter of exercise capacity. The changes in maximum tolerable exercise load were matched by those in ventilation and pulse rate at submaximal loads’. Improvements in pulse rate were not always present after operation and when they did occur they were quite modest. In normal animals and men stroke volume increases at the start of exercise but then tends to remain fairly constant, with increasing cardiac output being achieved by increase in heart rate (Rushmer 1959; Bevegard et al. 1960). This has been found to be true in patients with mitral valve disease irrespective of the cardiac rhythm (Donald et al. 1957; Holmgren et al. 1958) so that heart rate and cardiac output on exercise must be proportional. If we assume, as seems very likely, that the cardiac output required to achieve a given work-load was unchanged by operation in our patients with mitral valve disease, or even that it was

Exercise Tests and Heart Valve Replacement

193

slightly smaller, due to increased general fitness, then in those patients who did not have much lower heart rates after operation, forward stroke volumes were either unaffected by valve replacement or perhaps even reduced. This is not entirely an unexpected finding, In patients undergoing mitral valvotomy the clinical and physiological improvement has been found to be related to the severity of their condition before operation (Wade et al. 1954; Chapman et al. 1960). Our patients with mitral valve disease were fairly severely incapacitated and had long-standing disease, and the effects of this might not easily be reversible by correction of the mechanical abnormality. Ventilatory capacity was well preserved before operation in our patients, and more of them showed an improvement in the ventilatory response to exercise than in the heart rate response. One patient (Case 10) had severe irreversible airways obstruction which had got worse by the time of his postoperative study; in the remainder ventilatory capacity was unaffected by valve replacement. There remains a clear need for more detailed assessment of both haemodynamic and ventilatory exercise responses before and after operation to explore the apparent paradox between the subjective and objective observations. In this study we did not think it ethically defensible to measure cardiac output in patients who were submitted to other routine haemodynamic investigations, as an indwelling catheter during the exercise test would have been necessary. In future sudies this problem might be overcome by the use of arterialized ear lobe capillary blood samples (Godfrey et al. 1971; Spiro 1975) The maximum work rate achieved during the progressive exercise test has to be interpreted with caution as physical fitness, habituation and motivation may be important influences. Furthermore, measurement of maximum working capacity often causes extreme discomfort. Whilst the risks of exercise tests are small they are not negligible, especially in maximal exercise (Jokl & McClellan 1971). The interpretation of heart rate and ventilation responses to defined submaximal levels of energy expenditure (Spiro et al. 1974) is less dependent on motivation and causes less fatigue, whilst still demonstrating significant cardiorespiratory abnormality in disease (Spiro et al. 1975) and may provide a suitable alternative to maximal exercise testing. In future studies a constant work rate exercise test (steady-state together with measurement of blood gas tensions in addition to heart rate, ventilation and gas exchange, will allow calculation of cardiac output, alveolar-arterial oxygen gradient, percentage venous admixture and the dead space/tidal volume ratio. These parameters would also allow a more informative assessment of the contributions of the circulatory and ventilatory components of gas exchange on the limitation of exercise capacity in these patients. This preliminary report has indicated the obvious need for fuller, well-controlled exercise testing in patients undergoing heart valve replacement surgery. Whilst the results obtained in this study may not invalidate the subjective benefits of the operation or the effect on prognosis, they do suggest that valve replacement might better be performed earlier in the natural history of the disease.

ACKNOWLEDGEMENTS

We thank Professor J. F. Goodwin for advice and encouragement and we also thank him, Dr C. M. Oakley, Mr W. P. Cleland and Professor H. H. Bentall for permission to study patients under their care.

194 Requests for ton, Seattle,

, D. G. G&now,

S. G. Spiro, M. j? Raphael and S. Freedman

reprints to Dr S. G. Spiro, Division Washington 98195, USA.

of Respiratory

Diseases

RM-12,

University

of Washing-

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