Long-standing inflammatory conditions such as rheumatoid ahritis (RA) are associated with deposition of a form of amyloid known as AA (amyloid-associated protein), which may involve kidneys, hea, liver, skeletal muscle, and skin, for example. Amyloid deposition in the myocardium results in decreased compliance and impaired diastolic filling, i.e., restrictive cardiomyopathy. The myocardium has a rigid and waxy texture. This form of amyloid, as well as any other biochemical form, can be visualized on tissue section by staining with Congo red, which acquires a characteristic apple-green birefringence under polarized light. Constrictive pericarditis is due to any pathologic process that results in fibrous thickening of the pericardium, with resultant impaired compliance. Clinically, therefore, this condition manifests with a picture similar to restrictive cardiomyopathy because of impaired diastolic filling. Constrictive pericarditis is usually caused by previous episodes of acute pericarditis, especially hemorrhagic, suppurative, and caseous pericarditis. Dilated cardiomyopathy is characterized by massive ventricular dilatation and may be caused by genetic alterations, myocarditis, toxic insults (alcohol), metabolic disorders (hemochromatosis), etc. Most cases are idiopathic. The main pathophysiologic alteration is impaired contractility. You may be tempted to think that this patient is prone to developing hypersensitivity myocarditis, but this form of myocardial disease has been repoed after treatment with some antihypeensive agents,antibiotics, diuretics and not with coicosteroids or NSAIDs. Fuhermore, myocarditis manifests acutely with arrhythmias and hea failure, and chronically with dilated cardiomyopathy and congestive hea failure. Ref: Hoit B.D. (2011). Chapter 34. Restrictive, Obliterative, and Infiltrative Cardiomyopathies. In V. Fuster, R.A. Walsh, R.A. Harrington (Eds), Hurst's The Hea, 13e.