Noninvasive assessment of baroreflex sensitivity in post-MI patients by an open loop parametric model of RR-systolic pressure interactions

Noninvasive evaluation of baroreflex sensitivity is considered an important goal for diagnosis and prognosis in post-MI patients. Methodological approach and physiological measure conditions may be the main causes for the differences found with respect to the standard Phenylephrine test. In this study, three linear parametric models, describing variability and mutual interactions of RR interval and systolic arterial pressure (SAP), were compared in relation to their ability to quantify baroreflex gain, using the Phenylephrine test index (PheBRS) as reference. By monovariate autoregressive (AR) model, bivariate AR model and open loop ARXAR model, specific gain indexes (αAR, α2AR, αARXAR) were calculated. Variance and regression analysis selected αARXAR first in correlation with PheBRS, demonstrating that a better agreement is achieved using the ARXAR model, specifically designed to describe the causal influences of SAP on RR interval.