What happens to SVC flow in constrictive pericarditis during inspiration?

In constrictive pericarditis, the pericardium becomes thickened and less elastic, which limits the ability of the heart to expand and fill properly during diastole. When a patient with constrictive pericarditis inspires, intrathoracic pressure decreases. This drop in pressure usually facilitates increased venous return to the right heart, particularly from the superior vena cava (SVC). However, due to the constriction from the pericardium, the heart cannot accommodate this increase in return flow effectively.

As the right ventricle fills with blood, its capacity to expand is limited, leading to a decreased ability to accommodate the increased venous return from the SVC during inspiration. As a result, the observed effect in patients with constrictive pericarditis is a decrease in SVC flow during inspiration. This physiological response underscores the impact of constrictive pericarditis on hemodynamics, particularly how external constraints on the heart affect perfusion and filling dynamics.