BAROREFLEX SENSITIVITY IN MEN WITH RECENT MYOCARDIAL-INFARCTION - IMPACT OF AGE

We investigated the effect of age on baroreflex sensitivity (BRS) in 3 9 male patients, who had survived their first myocardial infarction (M I) and in 15 age-matched controls. BRS was inversely related to age in both MI patients (r = -0.632, P<0.0001) and controls (r = -0.706, P<0 .0001). The relationship between BRS and age, however, was significant ly different in MI patients as compared with healthy controls: BRS was markedly higher and the BRS-age regression slope was significantly st eeper in controls than in MI patients. As a consequence, the decrease in BRS caused by MI (Delta BRS = age-specific expected BRS-measured BR S) was related inversely to age (r = -0.66, P<0.05) i.e. Delta BRS was greatest among young MI patients. However, the relative BRS (BRS% = m easured BRS divided by the age-specific expected BRS) did not correlat e with age. The average BRS% of MI patients was 37% lower than that of controls. MI size and left ventricular (LV) systolic funciton did not correlate with BRS. BRS correlated with variables related to cardiac diastolic function (peak late LV filling rate r = 0.43, P<0.01, ratio of peak early to peak late LV filling rate r = -0.35, P<0.05), LV wall thickness (r = -0.34, P<0.05), exercise capacity (r = 0.31, P<0.05) a nd the extent of ST-depression during exercise (r = -0.40, P<0.05), bu t all these correlations lost their significance after the adjustment for age. In conclusion, age is a factor that should be taken into cons ideration when evaluating the mechanisms of BRS impairment associated with different diseases. We suggest that, in addition to BRS, variable s expressing the impairment of BRS (such as Delta BRS and BRS%) might be useful for the risk stratification of MI patients.