Right ventricular oxygen extraction at rest is ~50% compared to ~75% in the left ventricle, with the substantial extraction reserve mobilized preferentially during exercise.
Few studies have investigated factors responsible for the O 2 demand/supply balance in the right ventricle. Resting right coronary blood flow is lower than left coronary blood flow, which Is consistent with the lesser work of the right ventricle. Because right and left coronary artery perfusion pressures are Identical, right coronary conductance is less than left coronary conductance, but the signal relating this conductance to the lower right ventricular O 2 demand has not been defined. At rest, the left ventricle extracts ~75% of the O 2 delivered by coronary blood flow, whereas right ventricular O 2 extraction Is only ~50%. As a result, resting right coronary venous PO 2 is ~30 mm Hg, whereas left coronary venous PO 2 is ~20 mm Hg. Right coronary conductance does not sufficiently restrict flow to force the right ventricle to extract the same percentage of O 2 as the left ventricle. Endogenous nitric oxide impacts the right ventricular O 2 demand/supply balance by increasing the right coronary blood flow at rest and during acute pulmonary hypertension, systemic hypoxia, norepinephrine infusion, and coronary hypoperfusion. The substantial right ventricular O 2 extraction reserve is used preferentially during exercise-induced increases in right ventricular myocardial O 2 consumption. An augmented, sympathetic-mediated vasoconstrictor tone blunts metabolically mediated dilator mechanisms during exercise and forces the right ventricle to mobilize its O 2 extraction reserve, but this tone does not limit resting right coronary flow. During exercise, right coronary vasodilation does not occur until right coronary venous PO 2 decreases to ~20 mm Hg. The mechanism responsible for right coronary vasodilation at low PO 2 has not been delineated. In the poorly autoregulating right coronary circulation, reduced coronary pressure unloads the coronary hydraulic skeleton and reduces right ventricular systolic stiffness. Thus, normal right ventricular external work and O 2 demand/supply balance can be maintained during moderate coronary hypoperfusion.
Zong et al. (Thu,) conducted a review in Right ventricular oxygen demand/supply balance. Right ventricular oxygen extraction at rest is ~50% compared to ~75% in the left ventricle, with the substantial extraction reserve mobilized preferentially during exercise.