High prevalence of viral and immune myocarditis in patients with "idiopathic" and genetic dilated cardiomyopathy: biopsy proved diagnosis

Abstract

Purpose: To perform morphologic study of dilated cardiomyopathy's etiology and estimate the diagnostic value of other instrumental methods. Methods: 42 patients (30 men, 45.0±13.9 years) with dilated cardiomyopathy syndrome (average left ventricle diastolic diameter 6.8±0.9 cm, EF 25.9±11.1%) have undergone endomyocardial/intraoperative biopsy, autopsy or explanted heart examination with virus detection (PCR); anti-heart antibodies were also measured as well as EchoCG, myocardial scintigraphy (n=9), CT (n=21), MRI (n=13), coronary angiography (n=21). The control group included 20 patients with ischemic heart disease. Results: Morphologic study allowed to diagnose: 1) isolated myocarditis in 28 patients (19 – viral, 1 – bacterial, 1 – hypersensitive). In 7 patients productive vasculitis prevailed (none with systemic); in 4 patients myocarditis was combined with severe coronary atherosclerosis, in 2 – with bicuspid aortic valve; 2) ARVD + viral myocarditis in 2 patients (1 case also with noncompaction of the myocardium, NCM); 3) desminopathy + acute fatal myocarditis in 1 case; 4) TTR-amyloidosis in 1 case; 5) unverified storage disease with viral myocarditis and NCM in 1 case; 6) NCM in 5 patients (with myocarditis in 4 cases and viral genome in 2 cases); 7) unverified primary dilated cardiomyopathy in 4 patients (with viral genome in 2 cases). Viral genome in the myocardium (including mixt infection) was detected in 26 patients (61.9%): parvovirus B19 in 16 cases, herpes virus type 6 in 12 cases, Epstein-Barr virus in 9 cases, cytomegalovirus in 4 cases, and herpes simplex virus type 1/2 in 4 patients. Only 2 virus-positive patients (with primary cardiomyopathy) had no signs of myocarditis. In control group, the viral genome in the myocardium was found in 85% of patients but myocarditis was confirmed only in 25%. The most useful methods of diagnostics (in addition to history) were: specific antinuclear antibodies, high level of antibodies to conduction system (sensitivity for diagnostics of myocarditis was 52.9% and 85.3%, specificity and positive predictive value 100%) and general level of anti-heart antibodies, viral genome in the blood, late enhancement (CT), diffuse/local defects of perfusion by scintigraphy, pathologic Q/QS (for genetic diseases). Conclusions: Morphologic study revealed the immune-inflammatory nature of dilated cardiomyopathy in 66.7% of patients, isolated genetic cardiomyopathy in 14.3%, and their combination in 19.0%. We have developed an algorithm for nosologic diagnostics of dilated cardiomyopathy on the basis of combination of clinic, laboratory and instrumental signs.