Determinants of exercise tolerance after acute myocardial infarction in older persons

OBJECTIVES: Exercise tolerance is reduced with advancing age. Identificatio n of potentially reversible determinants of the age-related decrement in ex ercise tolerance, which remain largely unexplored in older subjects and in patients recovering from a recent myocardial infarction (MI), may have usef ul therapeutic implications. The objective of this study was to identify th e independent determinants of exercise tolerance in older patients with a r ecent MI. DESIGN, SETTING, AND PARTICIPANTS: Data is from baseline assessment of 265 post-MI patients (age range 45-85 years) enrolled in the Cardiac Rehabilita tion in Advanced Age randomized, controlled trial. Patients with major como rbidities or severe MI complications were excluded from the trial. Exercise tolerance was determined from symptom-limited exercise testing and express ed as total work capacity (TWC, kg.m) or peak oxygen consumption ((V) over dot o(2peak), mL/kg/min). The associations between both TWC and (V) over do t o(2peak) and baseline demographic, social, clinical, and neuropsychologic al variables and an index of health-related quality of life were determined with univariate and multivariate analysis. RESULTS: With univariate analysis, TWC decreased by 1285 kg.m per decade of increasing age between 45 and 85 years of age. With multivariate analysis, TWC decreased by 922 kg.m per decade. Increasing age (P < .001), female ge nder (P < .001), a small body surface area (P < .001), a low level of usual physical exercise before MI (P < .002), and the presence of post-MI depres sive symptoms (P < .024) were independently associated with a lower TWC. Th e same factors, in addition to a small arm muscle area (P < .002), were als o independently associated with a lower (V) over dot o(2peak). CONCLUSIONS: Age per se accounts for approximately 70% of the age-related d ecay in TWC or (V) over dot o(2peak) However, the inclusion of modifiable f actors such as physical exercise and depression in the prediction model rei nforces the importance of a multidimensional approach to the evaluation and treatment of older patients with a recent MI.