PATHOPHYSIOLOGY AND NATURAL HISTORY CONGENITAL HEART DISEASE Pathologic features of myocardial hamartomas causing childhood tachyarrhythmias

We have observed in 11 infants, aged 2 years or less, a distinct clinicopathologic lesion responsible for tachyarrhythmias that were fatal in 96% (25/26) of previously reported cases. Nine of the 11 patients, who underwent electrophysiologic mapping and surgical excision of the lesion, have survived, with follow-up periods ranging from 1 month to 6 years. The morphologic findings in these 11 patients and in the 26 cases cited in the literature are reviewed. Pathogenic considerations have included viral-induced lesions, cardiomyopathy, neoplasm, and developmental disorder of Purkinje cells. We believe this lesion to be a myocardial hamartoma. Supportive evidence includes prevalence in infants, tumorlike growth pattern without mitotic figures, and association of other developmental abnormalities. Through electrophysiologic mapping, this myocardial hamartoma is potentially accessible to surgical excision and long-term cure. Circulation 75, No. 4, 705-710, 1987. POTENTIALLY FATAL ventricular tachycardia in children 2 years old or younger may be caused by a localized myocardial abnormality that has been termed arachnocytosis of the heart muscle,1 isolated cardiac lipidosis,2 infantile cardiomyopathy with histiocytoid reaction,' infantile xanthomatous cardiomyopathy,4 focal lipid cardiomyopathy,5 focal myocardial degeneration,6 foamy myocardial transformation of infancy,7 idiopathic infantile cardiomyopathy,' histiocytoid cardiomyopathy of infancy,9 10 oncocytic cardiomyopathy, 1 and Purkinje cell tumor. 12, 13 Currently, electrophysiologic mapping may localize the abnormality so that curative surgical excision can be performed for this previously fatal condition. 14 In this study we present the morphologic findings in 11 recently treated patients (nine of whom survived), review previously reported cases, and discuss concepts of pathogenesis of this peculiar myocardial lesion. These 11 patients, who were referred to our institution between 1980 and 1986 because of symptomatic ventricular tachycardia, were found at operation to have a distinct morphologic lesion. From the Departments of Pathology and Pediatric Cardiology, Baylor College of Medicine and Texas Children's Hospital, and the Department of Surgery, Texas Heart Institute, Houston. Address for cortespondence: Debra L. Kearney, M.D., Department of Pathology, Baylor College of Medicine, One Baylor Plaza, Houston, TX 77030. Received Aug. 20, 1986; revision accepted Dec. 26, 1986. Methods Clinical evaluation included chest roentgenogram and twodimensional echocardiography. All patients underwent intracardiac electrophysiologic study with localization of the earliest site of endocardial activation. Surgical excision of the arrhythmogenic area was performed with cryoablation of the margins. Surgically excised myocardium was placed in Zenker's fixative for routine histologic examination, and sections were stained with hematoxylin and eosin, a modified Gomori's trichrome stain for connective tissue, and the periodic acid-Schiff stain for glycogen. Electron microscopic studies were performed on myocardium from eight of the 11 patients, with 2.5% glutaraldehyde fixation and staining with uranium acetate/lead citrate. An autopsy was performed on one of the two infants who died, and the heart, including the conduction system, was examined extensively.