Critical value of baroreflex sensitivity determined by spectral analysis in risk stratification after myocardial infarction

The risk of cardiac death in patients after MI is predicted by a decreased baroreflex sensitivity(BRS). The critical value of BRS based on phenylephri ne administration is 3 ms/mmHg. The aim of this study was to determine the critical value of BRS assessed by spectral analysis of spontaneous fluctuat ions in pulse intervals and blood pressure. Digital blood pressure was reco rded noninvasively (3 min, controlled breathing 0.33 Hz) in 112 patients, 8 -18 days after MI. Nine patients died during the first year after MI. BRS w ets determined as the gain between the spectrum of the variability of systo lic blood pressure and the cross-spectrum between the variability of pulse intervals and systolic blood pressure. The gain at the frequency of 0.1 Hz was taken as the measure of BRS. Sensitivity, specificity, and the positive predictive value were calculated in the range of 1-10 ms/mmHg in steps of 1 ms/mmHg. The value of BRS above which sensitivity no longer increases and specificity decreases was taken as the optimal value. The critical value o f BRS determined by spectral analysis wets 3 ms/mmHg (sensitivity 77%; spec ificity 71%). in conclusion, the spectral critical value of BRS determined by spectral analysis of spontaneous fluctuations in pulse intervals and blo od pressure corresponds to the value determined by the phenylephrine method .