ADDITIVE EFFECTS OF AGE AND SILENT-MYOCARDIAL-ISCHEMIA ON THE LEFT-VENTRICULAR RESPONSE TO UPRIGHT CYCLE EXERCISE

To separate the independent effects of age and silent myocardial ischemia on the left ventricular response to aerobic exercise, maximal upright cycle ergometry was performed in three groups: 8 clinically healthy older men [76 +/- 3 (SE) yr] with ischemic electrocardiogram (ECG) and TI scan responses to prior maximal treadmill exercise (old silent ischemic subjects), 16 age-matched men with normal ECG and TI scan responses (old controls), and 21 healthy young (33 +/- 1 yr) men (young controls). Although the left ventricular ejection fraction, end-diastolic volume index, and end-systolic volume index were similar in the three groups at rest, with increasing work loads there was a progressive increase in the end-diastolic volume index and a blunted decline in end-systolic volume index in the two older groups, which was most apparent in the old silent ischemic subjects. Thus, at peak effort, end-diastolic volume index was largest in old silent ischemic subjects (101 +/- 6 ml/m2), intermediate in old controls (85 +/- 6 ml/m2), and smallest in young controls (67 +/- 3 ml/m2) (P < 0.002); conversely, left ventricular ejection fraction was highest in young controls (85 +/- 2), intermediate in old controls (76 +/- 3), and lowest in the old silent ischemic group (66 +/- 2) (P < 0.001). At exhaustion the peak systolic pressure-end-systolic volume index was significantly lower in the silent ischemic group than in young controls (6 +/- 1 vs. 25 +/- 4 mmHg . ml-1. m-2, respectively; P < 0.001) with the old controls in between (16 +/- 5 mmHg . ml-1 . m-2). Thus the diminished aerobic capacity, cardiac dilatation, and blunted ejection fraction response to upright cycle ergometry associated with normative aging are exaggerated in asymptomatic older men with exercise-induced silent myocardial ischemia.