Q. Pathophysiology of constrictive pericarditis?
Ans.
The thickened and rigid pericardium causes constriction of the heart and restricts ventricular dialatation and diastolic filling of the ventricles. The thickened rigid pericardium can cause dissociation of intracardiac and intrathoracic pressures and elevation of diastolic intracardiac pressures. This results in systemic and pulmonary venous congestion. Since the early phase of ventricular relaxation is normal, the early filling of the ventricles take place normally. Further relaxation of ventricles are restricted by the thickened pericardium resulting in acute elevation of diastolic ventricular pressure which gives a square root (") appearance to the diastolic ventricular pressure tracing. Uniform constriction of all the four cardiac chambers results in equalization of diastolic pressures in all the four chambers. This is different from restrictive cardiomyopathy where the difference in diastolic pressure between ventricles will be more than 5 mm. of Hg. The myocardium is usually normal in structure and function. This results in good systolic function.
The ventricular filling takes place during early filling phase only as further filling is prevented by the thickened and rigid pericardium.