The role of right ventricular endomyocardial biopsy for idiopathic giant cell myocarditis

Background: Idiopathic giant cell myocarditis (GCM) is an uncommon cause of cardiac failure distinguished clinically from lymphocytic myocarditis by rapidly progressive heart failure, arrhythmias, and heart block. Unlike fulminant lymphocytic myocarditis, patients with fulminant cardiac failure caused by GCM may respond to certain immunosuppressive agents; however, right ventricular endomyocardial biopsy (EMB) is infrequently used to establish the diagnosis partly because the sensitivity of EMB for GCM is unknown. The purpose of this study was to estimate the sensitivity of right ventricular EMB for GCM in a referral population. Methods and Results: Twenty subjects (of 63 total) in the Multicenter Giant Cell Myocarditis Registry underwent both right ventricular EMB and heart pathology (HRTP) evaluation from apical wedge, explantation, or autopsy. The false-negative rate of right ventricular EMB was defined as the ratio of negative EMB to positive HRTP results. Ten of the 20 subjects were women. The mean age was 38 years (range, 16-53 years). Twelve (60%) subjects had a positive EMB and positive HRTP confirming GCM. Three (15%) had a negative EMB and positive HRTP for GCM. Five had a positive EMB and negative HRTP evaluation for GCM. The resulting sensitivity of EMB for GCM was 80% (12/15) with a positive predictive value of 71%. Assuming the 5 subjects with a positive EMB and negative HRTP are true positives, the sensitivity improves to 85% (17/20). Predictors of negative HRTP after positive EMB were time from symptom onset to HRTP (P = .006) and time from EMB to HRTP (P = .03). Conclusions: The sensitivity of right ventricular EMB is high in patients with GCM who have early disease presentation and a fulminant clinical course. Although these results may not apply to individuals with less aggressive disease, EMB may be used selectively to distinguish fulminant heart failure caused by GCM from other causes in which the prognosis may differ.