Systolic–diastolic coupling

The normally functioning heart delivers a steady supply of oxygen and nutrients to the body over a broad range of physiological states and loading conditions. Efficient cardiac performance at rest and during exercise is therefore a primary evolutionary directive for survival. The four-chambered heart is primarily a volume pump. It couples systolic and diastolic properties because of simultaneous reciprocal atrial filling and ventricular emptying, resulting in near-constant volume, four-chambered heart pumping with very slight variation (5%–7%) of the pericardial sac contents during one cardiac cycle. This is achieved by oscillatory motion of atrioventricular valve plane, while the epicardial apex and back of the atria remain spatially fixed. Ventricular filling is initiated through the spring-like recoil of the relaxing left ventricular chamber wall (myocardium) and associated tissues, converting part of stored end-systolic elastic strain into wall motion and diastolic suction of atrial blood. In this chapter, functional predictions regarding systolic–diastolic and atrioventricular interactions are presented from a kinematic framework and validated using human imaging and invasive measurements.