SILENT EXERTIONAL MYOCARDIAL-ISCHEMIA IN THE ELDERLY - A QUANTITATIVE-ANALYSIS OF ANGINAL PERCEPTUAL THRESHOLD AND THE INFLUENCE OF AUTONOMIC FUNCTION

OBJECTIVE: To assess the perception of angina in the elderly and its r elationship to autonomic function. DESIGN: Prospective cohort study of patients with exertional ischemia. SETTING: Medical, geriatric and ca rdiac outpatient clinics in two centers. PARTICIPANTS: All subjects ha d ischemic heart disease as evidenced by positive treadmill stress tes ts and, in some, diagnostic angiography and/or documented Q wave infar ction. In the first study (I), 37 older patients (range 70-82 years) a nd 39 younger patients (range 42-59 years) were studied. In a subseque nt study (II), a further 49 patients were divided into 2 groups: those with good perception of angina (Anginal Perception Threshold < 15 sec onds, group A, 26 patients) and those with no angina despite ischemia (group B, 23 patients). MEASUREMENTS: Anginal perceptual threshold (AP T), age, cardiovascular autonomic function, and blood pressure were me asured. APT was defined as the time between onset of 1 mm ST depressio n to the onset of angina during treadmill stress testing. Autonomic fu nction was studied using heart rate ratios before and after the valsal va maneuver, heart rate responses to deep breathing, and heart rate an d blood pressure responses to standing. RESULTS: In study I, APT in th e older patients was delayed by a median value of 49 seconds [79 (rang e 15-188) versus 30 (-99 to 97) seconds in the younger patients, P < 0 .001]. There was no significant correlation between prolonged APT and autonomic dysfunction when younger and older groups were analyzed inde pendently or together. When, however, the high APT subgroup (APT > 30 seconds) was analyzed separately, there was a significant correlation between APT prolongation and impaired valsalva response (r = -0.4; P < 0.005). In study II, 21 of 23 patients (91.3%) with positive exercise test but with no angina (group B) had at least one abnormal autonomic function test compared with 5 of 26 (19%) patients with good anginal perception (group A). Of note, group A was significantly younger than group B [60 (53-63) years vs 66 (62-70 years, P < 0.001]. CONCLUSION: Elevation of APT in the elderly suggests that warning of critical myoc ardial ischemia is delayed. Autonomic dysfunction may be one of the un derlying mechanisms.