Pattern of Right Ventricular Pressure Fall and Its Modulation by Afterload

J. CORREIA-PINTO, T. HENRIQUES-COELHO, S. MAGALHÃES,
A. F. LEITE-MOREIRA

Department of Physiology, Faculty of Medicine, University of Porto, Portugal

Received August 30, 2002
Accepted February 25, 2003

Summary
Pattern of right ventricular pressure (RVP) fall and its afterload dependence were examined by analyzing ventricular pressure curves and corresponding pressure‑dP/dt phase planes obtained in both ventricles in the rat heart in situ. Time and value of dP/dt_min, and the time constant τ were measured at baseline and during variable RV afterload elevations, induced by beat-to-beat pulmonary trunk constrictions. RVP and left ventricular pressure (LVP) decays were divided into initial accelerative and subsequent decelerative phases separated by corresponding dP/dt_min. At baseline, LVP fall was decelerative during 4/5 of its course, whereas only 1/3 of RVP decay occurred in a decelerative fashion. During RV afterload elevations, the absolute value of RV-dP/dt_min and RV-τ increased, whilst time to RV‑dP/dt_min decreased. Concomitantly, the proportion of RVP decay following a decelerative course increased, so that in highly RV afterloaded heartbeats RVP fall became more similar to LVP fall. In conclusion, RVP and LVP decline have distinct patterns, their major portion being decelerative in the LV and accelerative in the RV. In the RV, dP/dt_min, τ and the proportional contribution of accelerative and decelerative phases for ventricular pressure fall are afterload-dependent. Consequently, τ evaluates a relatively much shorter segment of RVP than LVP fall.

Key words
Right ventricle • Ventricular pressure fall • Relaxation time constant • Rat