ABSTRACT
The cardiovascular system consists of a right pump that provides circulation to the pulmonary circuit and a left pump that supplies the systemic circuit. Both systems operate simultaneously in a series arrangement and as such their outputs, over more than a few heartbeats, are normally equal. In 1918, Ernest Starling, using earlier data from Frank and others, formally stated the fact that “within limits, the greater the stretch on the myocardial muscles prior to contraction, the greater is the force of contraction.” This phenomenon is known as the Frank-Starling law of the heart. This fundamental principle of cardiac physiology explains the beat-to-beat adjustments that occur in balancing the output of the right and left ventricles as occurs during normal respiration.
