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 relationship to autonomic function.

DESIGN

Prospective cohort study of patients with exertional ischemia.

SETTING

Medical, geriatric and cardiac outpatient clinics in two centers.

PARTICIPANTS

All subjects had ischemic heart disease as evidenced by positive treadmill stress tests and, in some, diagnostic angiography and/or documented Q wave infarction. In the first study (I), 37 older patients (range 70-82 years) and 39 younger patients (range 42-59 years) were studied. In a subsequent study (II), a further 49 patients were divided into 2 groups: those with good perception of angina (Anginal Perception Threshold < 15 seconds, group A, 26 patients) and those with no angina despite ischemia (group B, 23 patients).

MEASUREMENTS

Anginal perceptual threshold (APT), age, cardiovascular autonomic function, and blood pressure were measured. APT was defined as the time between onset of 1 mm ST depression to the onset of angina during treadmill stress testing. Autonomic function was studied using heart rate ratios before and after the valsalva maneuver, heart rate responses to deep breathing, and heart rate and blood pressure responses to standing.

RESULTS

In study I, APT in the older patients was delayed by a median value of 49 seconds [79 (range 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 independently 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 myocardial ischemia is delayed. Autonomic dysfunction may be one of the underlying mechanisms.