DETECTION AND PROGNOSIS OF SILENT MYOCARDIAL ISCHEMIA

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Among 726 apparently healthy Baltimore Longitudinal Study of Aging (BLSA) men and women who have undergone serial maximal exercise testing since 1969, the risk of future cardiac events was compared in those whose initial test was positive (Group I), those who converted from negative to positive (Group II and those who remained negative over a 6.4 year mean followup (Group III). By proportional hazards analysis, Groups I and II had a nearly identical enhanced risk of a cardiac event (RR of 2.78 and 2.72 respectively) compared to Group III subjects. Thus, in asymptomatic volunteers, serial conversion from a negative to a positive exercise ECG has a similar predictive value for a future coronary event as an initially positive ECG response. To separate the effects of age and silent myocardial ischemia (SI), on the left ventricular (LV) response to maximal upright cycle ergometry, we compared 3 groups: 8 clinically healthy older men (mean age - 76) with prior abnormal ECG and thallium scan (TS) responses to maximal treadmill exercise (OSI); 16 age-matched men with normal ECG and TS responses (OC); and 21 young (mean age = 33) controls (YC). At rest LV ejection fraction (EF), end-diastolic volume index (EDVI) and end-systolic volume index (ESVI) were similar in the 3 groups. With cycle exercise LVEF increased markedly in the YC, less in the OC and least in the OSI. In contrast, exercise-induced LV dilatation (increased (ESVI) was most pronounced in the OSI with a lesser increase in the OC; EDVI actually declined below baseline values by maximal effort in the YC. Thus, age-related cardiac dilatation and blunted EF response to upright cycling are exaggerated in older subjects with exercise-induced SI.