Ventricular interdependence

Ventricular interdependence (or ventricular coupling) is a phenomenon wherewhereby the function of one ventricle is altered by changes in the filling of the other ventricle. This leads to increase in volume of one ventricle associated with a decreased volume in the opposite ventricle ¹.

This condition is classically seen in constrictive pericarditis (called the septal bounce sign). In constrictive pericarditis, the thickened, fibrotic, and/or calcified noncompliantnon-compliant pericardium results in a fixed volume of pericardial sac. The position of the interventricular septum depends on the relative pressure differences between the LVleft ventricle (LV) and the RVright ventricle (RV) throughout the cardiac cycle and is also influenced by respiration.

During early diastole there is rapid inflow of blood into the ventricles which causes a marked change in ventricular pressures. Because right ventricular filling begins slightly before left ventricular filling, the change in pressure equates to paradoxical leftward motion of the interventricular septum ². This phenomenon of ventricular interdependence or pathologic ventricular coupling leads to abnormal septal motion, called paradoxical septal motion or septal bounce . The septal bounce is accentuated during inspiration because of lower intrathoracic pressurepressures during inspiration when venous return to the right ventricle increases. This effect is reversed during exhalation when less blood is returned to the right ventricle ³. 

This phenomenon is also seen in constrictive pericarditiscardiac tamponade, pericardial tamponade, pulmonary hypertension, left bundle branch block, and right ventricular pacing ¹.