Right Ventricular Limitation: A Tale of Two Elastances.

Right ventricular (RV) dysfunction is a commonly considered cause of a low cardiac output in critically ill patients. Its management can be difficult and requires an understanding of how the RV limits cardiac output. We explain that RV stroke output is caught between the passive elastance of the RV walls during diastolic filling and the active elastance produced by the RV in systole. These two elastances limit RV filling and stroke volume, and consequently limit left ventricular (LV) stroke volume. We emphasize use of the term RV limitation and argue that limitation of RV filling is the primary pathophysiological process by which the RV causes hemodynamic instability. Importantly, RV limitation even can be present when RV function is normal. We use the term RV dysfunction to indicate that RV end-systolic elastance is depressed or diastolic elastance is increased. When RV dysfunction is present, RV limitation occurs at lower pulmonary valve opening pressures and lower stroke volume, but stroke volume and cardiac output still can be maintained until there RV filling i limited. We use the term RV failure to indicate the condition in which RV output is insufficient for tissue needs. We discuss the physiological underpinnings of these terms and implications for clinical management.