Final answer:
Distinguishing constrictive pericarditis from restrictive cardiomyopathy involves differentiating the heart's constriction by the pericardial sac versus stiffness in the myocardium, often through imaging studies such as echocardiogram and cardiac MRI.
Step-by-step explanation:
To distinguish constrictive pericarditis from restrictive cardiomyopathy, it's important to understand that these conditions affect the heart's function in different ways though they may cause similar symptoms such as shortness of breath and fatigue. Constrictive pericarditis is characterized by a thickened, fibrotic pericardial sac that restricts the heart's normal filling during diastole. On the other hand, restrictive cardiomyopathy involves stiffness within the myocardium itself, which also leads to diastolic dysfunction. Constrictive pericarditis is due to stiffened pericardial layers constricting the heart, while restrictive cardiomyopathy involves stiff myocardial tissue reducing ventricular compliance.
While physical examination and symptoms can be similar, imaging studies such as echocardiogram, cardiac MRI, and sometimes a cardiac catheterization provide the necessary details to differentiate between these conditions. An echocardiogram, for example, can show constriction of the heart by the pericardium in constrictive pericarditis or primary abnormalities in ventricular filling in restrictive cardiomyopathy. Additionally, a chest radiograph may show an enlarged cardiac silhouette in restrictive cardiomyopathy, while calcifications might be seen on CT scans in constrictive pericarditis. Detailed history taking may reveal possible causes like radiation therapy or cardiac surgery for pericarditis and systemic diseases like amyloidosis for cardiomyopathy. Furthermore, hemodynamic studies can show a dip-and-plateau or square root sign in ventricular pressure tracings in constrictive pericarditis, which is not typically seen in restrictive cardiomyopathy.