Diagnostic value of endomyocardial biopsies of the right ventricular septum in arrhythmias originating from the right ventricle.

The aim of the study was to classify the value of endomyocardial biopsies taken from the right ventricular septum in patients with ventricular tachyarrhythmias originating from the right ventricle. In a cohort of 62 young patients (mean age 35.6 years) 4-5 endomyocardial biopsies were taken from the right ventricular septum and myocardial atrophy, fibrosis and lipomatosis were analysed qualitatively and semi-quantitatively. Much interest was focused on the arrangement and type of fibrosis. Lipomatosis, myocardial atrophy and a finer form of fibrosis surrounding individual myocytes or groups of myocytes were judged as the typical histopathological findings of arrhythmogenic right ventricular dysplasia. The cohort of patients was subdivided clinically into idiopathic right ventricular outflow tract tachycardia (n = 50) and arrhythmogenic right ventricular dysplasia (n = 12). In the group of arrhythmogenic right ventricular dysplasia pathological findings were found in 92% with typical fibrolipomatosis in two cases, severe fibrosis ( > 40% per biopsy) in 5 cases, a finer form of fibrosis surrounding individual myocytes without lipomatosis in two cases and a slight interstitial or subendocardial fibrosis in two cases. In only one patient the endomyocardial biopsy was normal. In right ventricular outflow tract tachycardia normal endomyocardial biopsy findings predominated (80%). In two cases lipomatosis without fibrosis was a more or less normal finding, and in two other cases a slight interstitial or subendocardial fibrosis was found. Fibrosis was judged to be moderate or severe with discrete signs of inflammation in only two cases; in a long-term follow-up these two patients developed typical features of idiopathic dilated cardiomyopathy. Endomyocardial biopsies taken exclusively from the right ventricular septum were able to distinguish between right ventricular outflow tract tachycardia and arrhythmogenic right ventricular dysplasia, although the typical finding of fibrolipomatosis in cases with arrhythmogenic right ventricular dysplasia was rare. Characteristics of fibrosis are the key to the correct diagnosis provided that histopathological analysis is based on experienced qualitative criteria (type and arrangement of fibrosis). In conclusion, qualitative and semi-quantitative analyses of endomyocardial biopsies are far better than computerized quantitative methods. Biopsies from the free right ventricular wall cannot be generally recommended if a correct definition of arrhythmogenic right ventricular dysplasia in endomyocardial biopsies from the right ventricular septum is used.