Baroreflex sensitivity in men with recent myocardial infarction; impact of age

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Abstract
We investigated the effect of age on baroreflex sensitivity (BRS) in 39 male patients, who had survived their first myocardial infarction (MI) 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 significantly different in MI patients as compared with healthy controls: BRS was markedly higher and the BRS-age regression slope was significantly steeper in controls than in MI patients. As a consequence, the decrease in BRS caused by MI (ΔBRS=age-specific expected BRS—measured BRS) was related inversely to age (r=−0.66, P<0.05) i.e. ΔBRS was greatest among young MI patients. However, the relative BRS (BRS%= measured BRS divided by the age-specific expected BRS) did not correlate with age. The average BRS% of MI patients was 37% lower than that of controls. MI size and left ventricular (LV) systolic function 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) and the extent of ST-depression during exercise (r=−0.40, P<0.05), but all these correlations lost their significance after the adjustment for age. In conclusion, age is a factor that should be taken into consideration when evaluating the mechanisms of BRS impairment associated with different diseases. We suggest that, in addition to BRS, variables expressing the impairment of BRS (such as ΔBRS and BRS%) might be useful for the risk stratification of MI patients.

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