Baroreflex sensitivity in cardiac patients with chronic congestive heart failure: towards a non invasive assessment method

Spectral analysis of RR interval and systolic arterial pressure variability was applied for the non invasive assessment of the baroreflex gain in Congestive Chronic Heart Failure (CNF). Forty-nine CHF patients were studied during rest, controlled breathing and head-up tilt. The alpha index, a noninvasive measure of the overall gain of the RR to systolic arterial pressure (SAP) relationship, and a modified version called beta, incorporating the weighted coherence function, were computed in the low (LF) and high (NF) frequency bands by spectral analysis, and compared with the phenylephrine test slope. A linear model fitted on the beta index values during rest and controlled breathing showed a high correlation (r=0.93, Standard error of the estimation=2.5 ms/mmHg) with the phenylephrine test slope. In severe CNF patients the beta index proposed, evaluated during rest and controlled breathing, may improve the baroreflex gain estimation and provide a noninvasive assessment method that might be useful in gauging prognosis.