National Trends and Outcomes of Endomyocardial Biopsy for Patients With Myocarditis: From the National Inpatient Sample Database

Background: The utility of endomyocardial biopsy (EMB) in the management of myocarditis in the era of advanced cardiac imaging has been challenged. Methods and Results: The Nationwide Inpatient Sample Database (years 1998-2013) was queried to identify hospitalization records with a primary diagnosis of myocarditis, and underwent EMB procedure. We identified 22,299 hospitalization records with a diagnosis of myocarditis during the study period. Of those, 798 (3.6%) underwent EMB procedures. There was an average decrease in the incidence of EMB for myocarditis by 0.15% (P < .01) over the study period. Younger patients, women, and those with chronic kidney disease were more likely to undergo EMB. On multivariate analysis, patients with myocarditis who underwent EMB had higher in-hospital mortality (hazard ratio [HR] 1.97, 95% confidence interval [CI] 1.41-2.74) and longer median hospital stay (9 days vs 3 days; P < .001). EMB was associated with a higher incidence of cardiac tamponade (odds ratio [OR] 5.21, 95% CI 2.76-9.82), cardiogenic shock (OR 4.66, 95% CI 3.75-5.78), need for intra-aortic balloon pump (OR 3.52, 95% CI 2.49-4.97), and need for extracorporeal membrane oxygenation (OR 4.26, 95% CI 2.78-6.53). Conclusions: The use of EMB in hospitalizations with myocarditis has decreased over time. The use of EMB was associated with a higher likelihood of in-hospital mortality and morbidity. Whether these findings represent a causative association from the procedure or a consequence of more severe disease in this group could not be confirmed in this study.