Effect of myocardial ischaemia on left ventricular function and adaptability to exercise training.

PURPOSE: We evaluated the possible interaction between exercise-induced myocardial ischemia and abnormalities in left ventricular function in 72 patients with coronary artery disease at entry and upon discharge from a 6-month exercise training program. METHODS: Twenty-two patients with myocardial ischemia (MIS) defined by electrocardiographic and radionuclide imaging criteria constituted our experimental group (EG). Fifty patients without MIS were assigned to the control group for exercise training (CG-ET) and 31 healthy subjects to the control group for measures of left ventricular function (CG-LV). RESULTS: Both groups EG and CG-ET showed significant and comparable increases in peak oxygen uptake (EG: 25.2 +/- 5.1 to 26.9 +/- 5.4 mL x kg(-1) x min(-1), P < 0.02; CG-ET: 25.1 +/- 0.6 to 27.4 +/- 0.7 mL x kg(-1) x min(-1), P < 0.001) after exercise training, but only CG-ET showed significant reductions in heart rate, systolic blood pressure, and rate-pressure product during submaximal exercise. A significant increase in end-diastolic volume contributed to the increase in cardiac output during exercise in patients with MIS. Heart rate or treadmill time at onset of ST segment depression failed to increase as a result of training, and stroke counts and the product of stroke counts and heart rate showed a trend toward a decrease in response to exercise, suggesting progression of disease. CONCLUSIONS: Patients with myocardial ischemia showed improvements in maximal exercise capacity but failed to elicit physiologic adaptations during submaximal exercise or to increase the threshold for ischemia after exercise training. It is possible that the main emphasis in the management of this type of patient in a cardiac rehabilitation setting should be placed more on coronary risk factor modification to slow progression of disease than on improving cardiovascular efficiency.

Physiological benefits of a prolonged moderate-intensity endurance training programme in patients with coronary artery disease.

OBJECTIVES: To assess the physiological changes that take place in patients with coronary artery disease after 6 and 18 months of moderate-intensity endurance training. DESIGN: Prospective non-randomised controlled study. SETTING: Johannesburg Cardiac Rehabilitation Centre, a community-based phase III cardiac rehabilitation programme. SUBJECTS: The 93 patients who completed 18 months of training form the experimental or 'complier' group, while the 18 patients who discontinued the programme form the comparison or 'dropout' group. OUTCOME MEASURES: Haemodynamic, electrocardiographic and metabolic measurements at rest and at submaximal and peak exercise levels on admission and after 6 and 18 months of endurance training. RESULTS: Among the compliers several significant changes took place. Resting heart rate and blood pressure decreased at 6 months (P < 0.005). Submaximal heart rate, blood pressure, rate-pressure product and ventilation decreased at 6 months (P < 0.0001, P < 0.01, P < 0.001, P < 0.01 respectively), and the rate-pressure product decreased further at 18 months (P < 0.05). Ventilatory threshold increased at 6 months (P < 0.0001). Peak oxygen uptake, heart rate and ventilation increased at 6 months (P < 0.0001, P < 0.005 and P < 0.0001, respectively), with no further changes at 18 months. Treadmill time increased at 6 months and again at 18 months (P < 0.0001). The only significant change in the dropout group was an increase in ST-segment depression on the exercise ECG from 0.2 to 0.6 mm (P < 0.05). CONCLUSION: The study confirms that cardiac rehabilitation is beneficial. Most changes occurred in the first 6 months, the longer period of 18 months serving mostly as reinforcement of these and other lifestyle changes.

Ventilatory responses to exercise in patients with asymptomatic left ventricular dysfunction.

PURPOSE: Based on reports that patients with severe left ventricular (LV) dysfunction have a greater ventilatory response to effort than healthy people, we evaluated the ventilatory responses to effort of patients with coronary artery disease and various degrees of LV impairment before and after 6 months of exercise training in a community-based cardiac rehabilitation program. METHODS: Out of 171 patients consecutively referred for cardiac rehabilitation, 102 were enrolled in the study. Fifteen patients were excluded because of lung disease and 54 because of poor adherence to the exercise program. Patients were divided into three groups according to their ejection fraction (EF): Group 1 (G1) included 63 patients with EF > or = 50%, Group 2 (G2) included 21 patients with EF > or = 35 and < 50% and group 3 (G3) included 18 patients with EF < 35%. Peak oxygen uptake, minute ventilation (V(E)), and minute carbon dioxide production (VCO2) were measured before and after training in all participants. RESULTS: All groups showed a significant increase in peak oxygen uptake and treadmill time after training (G1: P = 0.0001 and P = 0.0001; G2: P = 0.0001 and P = 0.001; G3: P = 0.01 and P = 0.01; respectively). Patients in G3 had a significantly higher V(E)/VCO2 ratio than patients in G2 and G1 at 9 min and peak exercise, before (9 min: P = 0.046 and P = 0.025, peak: P = 0.024 and P = 0.002, respectively) and after training (9 min: P = 0.011 and P = 0.005, peak: P = 0.001 and P = 0.0001, respectively). The slope of the relation V(E) to VCO2 was significantly higher in G3 patients than in those in G2 and G1 (P = 0.0001, respectively) and was not reduced by exercise training in any group. CONCLUSIONS: Patients with severe LV dysfunction had a greater ventilatory response to exercise than those with moderately impaired or normal LV function. Exercise training increased the effort tolerance of all patients irrespective of their degree of LV dysfunction but failed to reduce the higher ventilatory responses to effort of patients with EF below 35%.

Should all cardiac patients be offered the choice of cardiac rehabilitation?

OBJECTIVE: To determine whether cardiac rehabilitation services are beneficial to patients and cost-effective. DESIGN: Several recent publications are reviewed. The first of these, 'Cardiac Rehabilitation. Clinical Practice Guideline No. 17', is itself a review of original published research: 900 scientific reports were examined by a multidisciplinary panel and 334 of these were considered to be of sufficient scientific merit to be used as the references for the guideline. The other publications discussed are: The American Heart Association Consensus Panel Statement, 'Preventing heart attack and death in patients with coronary disease', the American College of Cardiology's recommendations on 'Matching the intensity of risk factor management with the hazard for coronary disease events' and Recommendations of the Task Force of the European Society of Cardiology, the European Atherosclerosis Society and European Society of Hypertension, 'Prevention of coronary heart disease in clinical practice'. RESULTS: Cardiac rehabilitation brought about substantial benefits in risk factor profiles, including improvement in exercise tolerance, blood lipids, psychosocial well-being, and reduction in cigarette smoking and stress levels. In addition there was well-documented proof of improvement of pathophysiological measures, such as relief of symptoms, less progression and greater regression of disease and a reduction in mortality. As an intervention, cardiac rehabilitation was shown to be as cost-effective as many pharmacological regimens and surgical interventions. CONCLUSIONS: The evidence in support of cardiac rehabilitation is so overwhelming that all patients should be educated about this form of treatment and have the ultimate choice of accepting or rejecting it.

Predictors of exercise capacity and adaptability to training in patients with coronary artery disease.

PURPOSE: Systolic left ventricular dysfunction is a weak predictor of exercise tolerance in patients with chronic congestive heart failure. This study aimed to determine physiologic and other predictors of effort tolerance and adaptability to training in a wide variety of patients with coronary artery disease. METHODS: One hundred seventy-one patients (group 0) with documented coronary artery disease and various degrees of left ventricular dysfunction were enrolled into a medically supervised exercise training program for 6 months. One hundred six patients had an ejection fraction greater than 50% (group 1), 38 patients between 35% and 50% (group 2), and 27 patients less than 35% (group 3). RESULTS: Resting parameters of systolic and diastolic left ventricular function did not predict the effort tolerance of patients with coronary artery disease at any level of left ventricular impairment. Noncardiac factors including age, gender, Broca index, and forced vital capacity explained 50% of the variation in peak oxygen uptake in group 0. Peak oxygen uptake, ventilatory threshold, and treadmill time to exhaustion increased significantly after training in all groups. The magnitude of the improvement in these variables was the same for all groups. CONCLUSIONS: Noncardiac factors were better predictors of the effort tolerance of patients with coronary artery disease than parameters of left ventricular function at entry to an exercise program or after 6 months of training. A similar degree of adaptation to training was seen in all patients regardless of their degree of left ventricular systolic or diastolic dysfunction.

Is severe left ventricular dysfunction a contraindication to participation in an exercise rehabilitation programme?

OBJECTIVE: To evaluate the effects of an exercise training programme on patients with chronic left ventricular dysfunction. DESIGN: Intervention, before and after the trial. SETTING: Johannesburg Cardiac Rehabilitation Centre, a phase III community-based cardiac rehabilitation facility. PATIENTS: A consecutive sample of 28 patients who were recovering from acute myocardial infarction and who had a left ventricular ejection fraction of 30% or less. Twenty two patients completed the exercise training programme. INTERVENTION: A medically supervised exercise training programme of 6 months' duration. Type of exercise: walking, jogging or cycling. Intensity: 65-85% of the patient's maximal heart rate achieved during treadmill testing. DURATION: 30-45 minutes. Frequency: 3 times a week. Patients who attended fewer than 60% of all prescribed sessions were considered drop-outs. MAIN OUTCOME MEASURES: Haemodynamic, left ventricular function and effort tolerance parameters before and after training. RESULTS: Patients who completed the exercise training programme showed a significant improvement in maximal exercise capacity and a significant reduction in their cardiovascular demands during submaximal exercise. Peak oxygen consumption was increased by 12% after training (19.4 +/- 3 v. 21.8 +/- 4.8 ml/kg/min; P < 0.05) and exercise time to exhaustion by 33% (527 +/- 171 v. 700 +/- 186 seconds; P < 0.001). The double product at the same submaximal workload was significantly reduced (214 +/- 52 v. 194 +/- 44 beats/min x mmHg x 10(2); P < 0.05). These benefits were achieved without any adverse effects on resting (25.4 +/- 5 v. 28.5 +/- 7.9%; P < 0.05) or exercise (27.3 +/- 7.7 v. 29.9 +/- 9.5%; P > 0.05) left ventricular ejection fraction. CONCLUSIONS: Our results show that patients with chronic left ventricular dysfunction can benefit from an exercise training programme and that those benefits can be achieved without risk of further deterioration in left ventricular function. Physical training constitutes another therapeutic option which could be added to the comprehensive management of these patients.

Multivariate models for compliance with phase 3 cardiac rehabilitation services in Johannesburg.

The efficacy of an exercise cardiac rehabilitation programme depends on an adequate compliance of its participants. A 50% dropout rate after 12 months has been reported by most rehabilitation programmes. Compliance with attendance and the exercise prescription are monitored daily at the Johannesburg Cardiac Rehabilitation Centre. This study evaluated the attendance of 711 patients admitted to the programme between June 1986 and March 1990 and looked at possible differences in attendance and intensity rates of compliers and dropouts prior to dropout. Multiple regression analyses were performed on all patients using different measures of exercise compliance as dependent variables and patient characteristics on admission as explanatory variables in order to establish possible associations which could identify potential dropouts at an early stage. We found that 36% of patients dropped out by 12 months and that 50% managed to complete our 18 month programme. Dropouts complied less than compliers in terms of attendance and intensity before dropping out. Significant associations were found between the measures of compliance and patient characteristics. Age, smoking, peak oxygen uptake and a measure of hostility were identified as predictive factors. With the exception of the energy expended per session the variation in the other measures of compliance was poorly explained by the explanatory variables suggesting that other factors could be related to compliance at the Johannesburg Cardiac Rehabilitation Centre and need to be further evaluated.

The Johannesburg cardiac rehabilitation programme.

Cardiac rehabilitation has become a generally accepted mode of treatment for patients suffering from coronary artery disease. The Johannesburg cardiac rehabilitation programme was started in 1982 and has rapidly grown to become one of the largest programmes in southern Africa. This paper describes the 387 patients admitted to the unit between June 1986 and July 1988 and evaluates the effects of a combined exercise training and lifestyle modification programme. The mean age on admission was 55 years for males and 58 years for females. Most patients were from social classes I and II. Myocardial infarction, coronary artery bypass graft and a combination of both were the most common reasons for admission (35.4%, 23% and 21.2% respectively). On admission 72.9% of patients were smokers, 26.3% had hypertension and 34.3% had hypercholesterolaemia. A 50% drop-out rate within 12 months of starting the programme was noted. An increase in peak oxygen uptake, weight and skinfold thickness reduction, and improvement in the lipogram were seen after 6 months in patients who complied well with the programme. Cardiac rehabilitation is a secondary preventive strategy that can complement traditional medical and surgical therapies.

Exercise-related cardiac arrest in cardiac rehabilitation. The Johannesburg experience.

Prescribed physical activity plays a major role in the rehabilitation of patients with coronary artery disease, and as with any other form of treatment its benefits must be weighed against its possible risks. This study attempted to establish the safety of cardiac rehabilitation as a medical intervention at the Johannesburg Cardiac Rehabilitation Centre from its inception in September 1982 to July 1988, and analyses the medical status of patients who suffered a cardiac arrest (CA) in order to determine possible factors predictive of sudden death. Between September 1982 and July 1988, 1,574 patients were admitted to the unit; 480,000 man-hours of exercises were accumulated with 4 episodes of CA, giving an incidence of CA of 1/120,000 patient-hours. Three of the 4 episodes were fatal, giving an incidence of fatal CA of 1/160,000 patient-hours. This incidence is acceptably low and comparable with other cardiac rehabilitation programmes, making exercise as prescribed at the Johannesburg Cardiac Rehabilitation Centre a safe form of medical intervention. Patients at risk of CA during exercise were essentially not identifiable, since they did not come from a group currently recognised as at particularly high risk. A combination of inferior infarction with occluded dominant right coronary artery, good collateralisation and asymptomatic ischaemia was present in all CA patients. The likelihood of these pathological features being predictors of exercise-related sudden death requires further investigation.