Physiological coupling between the right ventricle and pulmonary circulation

Abstract

The article summarizes the main characteristics of the physiological coupling between the right ventricle (RV) and the pulmonary circulation. This coupling enables protecting pulmonary capillaries based on various coordinated mechanisms including: 1) the maintenance of a low pulmonary artery pressure at rest and on exercise (low resistance/high capacitance of the pulmonary circulation); 2) the sequential contraction of the RV and the resistive function of the conus preventing the transmission of acute increases in pressure; 3) the capacitive function of the RV chamber due to its high compliance; and 4) the fact that cardiac output levels off because the vena cava collapses at 0 mmHg right atrial pressure (RAP) and below. The low RV compliance facilitates venous return by ensuring low RAP, i.e., the downstream pressure of systemic venous return. The RV systolic function is influenced by afterload (steady and pulsatile), preload, inotropy and heart rate. The RV systolic function is also influenced by respiration (thoracic pump), ventricular interdependence (involving the interventricular septum and pericardium), and tricuspid valve function. Impaired coupling between the RV and pulmonary circulation is involved in the pathophysiology of various diseases (especially pulmonary hypertension) leading to heart failure. The optimization of the coupling between patient’s respiratory status, volemic status and RV load helps limiting the deleterious hemodynamic consequences of mechanical ventilation.