The heart may be involved in a number of systemic syndromes. Many of these have been mentioned briefly in other sections of this chapter, particularly those that can result in pulmonary hypertension or large vessel vasculitis. The pericardium, myocardium, heart valves, and coronary arteries may be involved either singly or in various combinations. In most cases the cardiac manifestations are not the dominant feature, but in some it is the primary cause of symptoms and may be fatal.
The most common type of myocardial involvement is an infiltrative cardiomyopathy, such as systemic amyloidosis, sarcoidosis, hemochromatosis, Fabry disease, or glycogen storage disease. These result predominantly in a restrictive cardiomyopathy. Cardiac calcinosis can occur in hyperparathyroidism (usually the secondary form) and in primary oxalosis. A number of muscular dystrophies can cause a cardiomyopathic picture (particularly Duchenne, less frequently myotonic dystrophy, and several rarer forms). Involvement of the heart in Duchenne dystrophy can result in a focal cardiomyopathy of the posterior wall; the classic ECG has prominent anterior precordial forces. In addition to LV dysfunction and heart failure, these conditions frequently cause conduction abnormalities, which may be the presenting or only feature. The myocardium may also be involved in inflammatory and autoimmune diseases. It is commonly affected in polymyositis and dermatomyositis, but usually this is subclinical. While systemic lupus erythematosus, scleroderma, and mixed connective tissue disease may cause myocarditis, these more commonly involve the pericardium, coronary arteries, or cardiac valves. Several endocrinopathies, including acromegaly, thyrotoxicosis, myxedema, and pheochromocytoma, can produce dilated cardiomyopathies that resolve when the underlying disease is appropriately treated. Similarly, the heart may be involved transiently in Guillain-Barré syndrome.
Pericardial involvement is particularly common in many of the connective tissue diseases. Systemic lupus erythematosus may present with pericarditis, and pericardial involvement is not uncommon (but is less frequently symptomatic) in active rheumatoid arthritis, systemic sclerosis, and mixed connective tissue disease. Endocardial involvement takes the form of patchy fibrous—predominantly on the right side—or inflammatory or sclerotic changes of the heart valves. At times, thrombosis and marantic (Libman-Sacks) endocarditis may occur and cause valvular dysfunction. Patients with antiphospholipid syndrome may present with coronary occlusion or stroke at a young age. Carcinoid heart disease results from the layering of plaque-like material over the tricuspid valve, RV endocardium, and pulmonic valve and presents with right heart failure due to tricuspid and pulmonary valve regurgitation. Left heart structures may be involved with carcinoid if there is an associated PFO or ASD. The hypereosinophilic syndromes involve the endocardium, leading to restrictive cardiomyopathy. A variety of arthritic syndromes are associated with aortic valvulitis or aortitis with resulting aortic regurgitation. These include ankylosing spondylitis, rheumatoid arthritis, and reactive arthritis (formerly called Reiter syndrome). Disorders of collagen (Marfan syndrome is the most frequent, followed by Ehlers-Danlos syndrome, then the Loeys-Dietz syndrome) often affect the ascending aorta, with resulting aneurysmal dilation and aortic regurgitation and susceptibility to aortic dissection. Mitral valve prolapse is also a common finding in these disorders.