Cardiovascular magnetic resonance risk stratification in patients with clinically suspected myocarditis

Background: The diagnosis of myocarditis is challenging due to its varying clinical presentation. Since myocarditis can be associated with significant 5-year mortality, and postmortem data show myocarditis in almost 10% of all adults suffering sudden cardiac death, individual risk stratification for patients with suspected myocarditis is of great clinical interest. We sought to demonstrate that patients with clinically suspected myocarditis and a normal cardiovascular magnetic resonance (CMR) according to our definition have a good prognosis, independent of their clinical symptoms and other findings. Methods: Prospective clinical long-term follow-up of consecutive patients undergoing CMR for work-up of clinically suspected myocarditis at our institution in 2007-2008. Results: Follow-up was available for n = 405 patients (all comers, 54.8% inpatients, 38% outpatient referrals from cardiologists). Median follow-up time was 1591 days. CMR diagnosis was myocarditis in 28.8%, normal in 55.6% and other pathology in 15.6%. Normal CMR was defined as normal left ventricular (LV) volumes and normal left ventricular ejection fraction (LV-EF) in the absence of late Gadolinium Enhancement (LGE). The overall mortality was 3.2%. There were seven cardiac deaths during follow-up, in addition one aborted SCD and two patients had appropriate internal cardioverter defibrillator (ICD) shocks - all of these occurred in patients with abnormal CMR. Kaplan-Meier analysis with log-rank test showed significant difference for major adverse cardiac events (cardiac death, sudden cardiac death (SCD), ICD discharge, aborted SCD) between patients with normal and abnormal CMR (p = 0.0003). Conclusion: In our unselected population of consecutive patients referred for CMR work-up of clinically suspected myocarditis, patients with normal CMR have a good prognosis independent of their clinical symptoms and other findings.