Spontaneous baroreflex sensitivity: Prospective validation trial of a novel technique in survivors of acute myocardial infarction

BackgroundLow baroreflex sensitivity (BRS) indicates poor prognosis after acute myocardial infarction. Noninvasive BRS assessment is complicated by nonstationarities and noise in electrocardiogram and pressure signals. Phase-rectified signal averaging is a novel signal processing technology overcoming these problems.ObjectiveTo prospectively validate a BRS measure (baroreflex sensitivity assessed by means of phase-rectified signal averaging [BRSPRSA]) based on this technology.MethodsNine hundred forty-one consecutive acute myocardial infarction survivors aged 80 years or younger in sinus rhythm were prospectively enrolled at 2 German university hospitals. All patients underwent 30-minute recordings of electrocardiogram and arterial blood pressures (Portapres; TNO-TPD Biomedical Instrumentation, Amsterdam, Netherlands) within the first 2 weeks after myocardial infarction. BRSPRSA was prospectively dichotomized at 1.58 ms/mm Hg. Primary end point was all-cause mortality at 5 years. Multivariable analyses included Global Registry of Acute Coronary Events score (dichotomized at ≥120), sex, BRSPRSA, left ventricular ejection fraction (dichotomized at ≤35%), and diabetes mellitus. BRSPRSA was compared with 3 standard noninvasive BRS measures, that is, the sequence method, the transfer function method, and the correlation method.ResultsDuring follow-up, 72 patients (7.7%) died. BRSPRSA stratified the study population into a high-risk group of 405 patients (≤1.58 ms/mm Hg) with an estimated 5-year mortality of 14.2% and a low-risk group of 536 patients (>1.58 ms/mm Hg) with a 5-year mortality of 2.8% (P <.0001). On multivariable analysis, BRSPRSA ≤ 1.58 ms/mm Hg was associated with a hazard ratio of 3.1 (confidence interval 1.7–5.6; P = .001). Predictive power of BRSPRSA ≤ 1.58 ms/mm Hg was particularly strong in patients with a Global Registry of Acute Coronary Events score of ≥120 or with a left ventricular ejection fraction of ≤35%.ConclusionBRSPRSA is a powerful and independent predictor of mortality in postinfarction patients especially when assessed in patients with a Global Registry of Acute Coronary Events score of ≥120 or a left ventricular ejection fraction of ≤35%.