Pathophysiology
Constrictive pericarditis is due to a thickened, fibrotic pericardium that forms a non-compliant shell around the heart. This shell prevents the heart from expanding when blood enters it. This results in significant respiratory variation in blood flow in the chambers of the heart.
During inspiration, the negative pressure in the thoracic cavity will cause increased blood flow into the right ventricle. This increased volume in the right ventricle will cause the interventricular septum to bulge towards the left ventricle, leading to decreased filling of the left ventricle. Due to the Frank–Starling law, this will cause decreased pressure generated by the left ventricle during systole.
During expiration, the amount of blood entering the right ventricle will decrease, allowing the interventricular septum to bulge towards the right ventricle, and increased filling of the left ventricle and subsequent increased pressure generated by the left ventricle during systole.
This is known as ventricular interdependence, since the amount of blood flow into one ventricle is dependent on the amount of blood flow into the other ventricle.
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