Effects of cardiac rehabilitation in diabetic patients: both cardiac and noncardiac factors determine improvement in exercise capacity

Abstract

Background: Diabetic patients have a worse prognosis than nondiabetic patients after myocardial infarction. Although exercise improves risk factors, exercise capacity, and mortality, it is still unclear if these benefits are the same as in nondiabetics. Furthermore, although exercise tolerance is predicted by systolic and diastolic dysfunction in nondiabetics, its role as a predictor of exercise capacity in diabetics remains unclear.

Hypothesis: Diabetics and nondiabetics see a similar improvement in their cardiac risk factors and exercise parameters from exercise-based cardiac rehabilitation (CR).

Methods: A series of 370 diabetics and 942 nondiabetics entered a 36-session outpatient CR program after interventions for coronary heart disease or after bypass or cardiac valve surgery. The program consisted of physical exercise, lifestyle modification, and pharmacotherapy.

Results: Quality of life, weight, blood pressure, and lipid profiles improved significantly in both groups during the 12-week program. Baseline metabolic equivalents (METs) were lower in diabetics vs nondiabetics at the start of CR (2.4 vs 2.7, P < 0.001). Although both groups increased their exercise capacity, diabetics had less improvement (change in METs 1.7 vs 2.6, P < 0.001). Significant predictors for improvement after CR included age, sex, and weight, as well as both systolic and diastolic function. After adjustment for these, diabetes remained a significant predictor of reduced improvement in exercise capacity.

Conclusions: Diabetics saw a significant benefit in quality of life, weight, exercise tolerance, and cardiac risk factors, but to a lesser extent when compared with nondiabetics. The mechanisms for poorer improvement in diabetics following CR also include noncardiac factors and require further study.

Figure 1

Mean metabolic equivalents (METs) during cardiac rehabilitation in diabetic (circles) and nondiabetic patients (diamonds). † = P < 0.01 vs baseline.

Figure 2

Mean change in metabolic equivalents (mean Δ METs) from baseline to peak in males (white bars) and females (gray bars), by diabetic status. Numbers above bars indicate mean value and range of values. † = P < 0.05 vs males; ‡ = P < 0.05 vs diabetic patients. Abbreviations: CI, confidence interval; METs, metabolic equivalents.

Figure 3

Mean change in metabolic equivalents (mean Δ METs) from baseline to peak in patients with normal (white bars) and abnormal diastolic function (gray bars), by diabetic status. Numbers above bars indicate mean value and range of values. †P < 0.05 vs normal diastolic; ‡P < 0.05 vs diabetic patients. Abbreviations: CI, confidence interval; METs, metabolic equivalents.