Primary myocardial disease

The disease is characterized by the presence of fibroelastic tissue over the endocardium. Usually the left ventricle, the left atrium, or both are involved, and characteristically there is invasion of subendocardial tissue. The endocardial surface usually is covered homogeneously by a glistening white layer that resembles an iced cake. The distribution, however, may be patchy. Endocardial fibroelastosis of the left ventricle has been classified into two types: the dilated variety with a large ventricle, and the contracted type with a small or contracted left ventricle. In rare instances, there is fibroelastosis of the right ventricle. Endocardial fibroelastosis may involve the mitral, and, less commonly, the aortic valve. Endocardial fibroelastosis is often associated with congenital anomalies of the heart, particularly coarctation of the aorta, aortic stenosis, aortic atresia, or Pompe's disease. These types of endocardial fibroelastosis will be excluded from this review by definition. This cardiomyopathy was first described by Stein in South Africa in 1964. That same year, we saw a patient with idiopathic nonobstructive cardiomyopathy at the University of Texas Medical Branch. Becker reviewed the clinical details and autopsy slides of this case and agreed that is was similar to that seen in the Bantus of South Africa. Unlike the situation among the Bantus, however, idiopathic nonobstructive cardiomyopathy is widespread but uncommon in the United States. Among the variety of names used to describe this condition is idiopathic mural endocardial disease. Clinically idiopathic nonobstructive cardiomyopathy is characterized by the onset of cardiac failure in a child about five years of age. Onset is usually not sudden. There are several theories concerning etiology, hemodynamics, and pathology, but these will not be discussed here. There has been a movement away from the title 'idiopathic hypertrophic subaortic stenosis' to emphasize the importance of the asymmetric septum in diagnosis. Asymmetric septal hypertrophy was first described by Schmincke in 1907. It is less commonly diagnosed in children than in adults. The reason for this may be a lack of familiarity with the condition and the difficulty in eliciting the physical signs at a young age, but the condition may be diagnosed in infancy and even in neonates. Asymmetric septal hypertrophy is characterized by hypertrophy of the ventricular septum and thickening of the free wall of the left ventricle and sometimes of the right ventricle. Thickened endocardium may be present on the hypertrophiedleft ventricle and part of the mitral valve opposite it. The hypertrophied muscle may result in the obstruction of the outflow tract in one or both ventricles during systole. The anterior leaf of the mitral valve may be relatively immobilized by endocardial thickening, resulting in mitral insufficiency. In 1952 and 1956 it was demonstrated that coxsackie virus caused myocarditis. Although many other agents have been implicated since that time, coxsackie virus remains the single most frequent cause of myocarditis. Coxsackie virus disease can occur in epidemic form, whereas those caused by other agents are usually isolated cases. The role of acute myocarditis in the evolution of diseases such as endocardial fibroelastosis is under discussion. Formerly, mumps virus was thought to be a cause of endocardial fibroelastosis, but Nadas and others seem to have refuted this. The combination of myocarditis and the subsequent increased stress of the myocardium, along with metabolic derangements and possible autoimmune disease, may contribute to the development of true cardiomyopathies. Pompe's disease, also known as type II glycogenosis, is inherited as an autosomal recessive, secondary to the absence of lysosomal α-1,4 glucosidase (acid maltase). The disease is characterized by storage of glycogen in lysosomes of all body tissues, especially the heart. In spite of the generalized nature of the disease, it has been called glycogen storage disease of the heart.