LONG-TERM OUTCOME OF PATIENTS WITH BIOPSY-PROVED MYOCARDITIS - COMPARISON WITH IDIOPATHIC DILATED CARDIOMYOPATHY

Objectives. The study objectives were 1) to assess the long term outco me of patients with biopsy-proved lymphocytic myocarditis (Dallas crit eria), and 2) to compare the outcome of these patients with that of pa tients,vith idiopathic dilated cardiomyopathy. Background. Endomyocard ial biopsy is frequently performed in patients presenting with dilated cardiomyopathy to identify lymphocytic myocarditis. Most previous stu dies of the natural history of myocarditis were performed before the e stablishment of the Dallas criteria. Thus, it is important to evaluate the prognostic value of positive endomyocardial biopsy findings in pa tients presenting with dilated cardiomyopathy, using standardized crit eria for lymphocytic myocarditis. Methods. All endomyocardial biopsy r esults from the Mayo Clinic (October 1979 to April 1988) with a diagno sis of myocarditis were reclassified according to the Dallas criteria. Patients whose biopsy specimens showed borderline or lymphocytic myoc arditis were included in the study group; those with systemic inflamma tory diseases known to be associated with myocardial involvement were excluded. Study group survival was compared with that for a cohort of patients with idiopathic dilated cardio myopathy seen at the Mayo Clin ic from 1976 to 1987 who had endomyocardial biopsy findings negative f or myocarditis. Results. Biopsy specimens from 41 patients met the Dal las criteria for a diagnosis of myocarditis (n = 28) or borderline myo carditis (n = 13). Of these 41 patients, 9 were excluded because of th e presence of systemic diseases known to be associated with myocarditi s, and 5 patients were excluded because of lack of available follow-up data. The myocarditis study group therefore included 27 patients (10 with borderline myocarditis, 17 with myocarditis). Fifty-eight patient s with a diagnosis of idiopathic dilated cardiomyopathy who underwent endomyocardial biopsy served as the comparison cohort. Ejection fracti on was lower in patients with idiopathic dilated cardiomyopathy ([mean +/- SD] 25 +/- 11%) than in those with myocarditis (38 +/- 19%, p = 0 .001), even though a higher proportion of myocarditis group patients w ere in New York Heart Association functional class III or IV (63%) tha n patients in the dilated cardiomyopathy group (30%, p = 0.005). There was no difference in 5-year survival rate between the myocarditis and idiopathic dilated cardiomyopathy groups (56% vs. 54%, respectively). Conclusions. This study demonstrates that the long-term outcome of pa tients,vith biopsy-proved myocarditis seen in a referral setting is po or, although no different from that of patients with idiopathic dilate d cardiomyopathy. With the current lack of proved effective treatment for lymphocytic myocarditis and no demonstration of survival benefit f or patients with myocarditis, these data suggest that endomyocardial b iopsy performed to exclude myocarditis is of limited prognostic value in the routine evaluation of dilated cardiomyopathy.