Outcomes of Heart Block in Myocarditis: A Review of 31,760 Patients

Background Various electrocardiographic abnormalities, including atrioventricular conduction block, have been reported in patients with myocarditis. We performed an observation study to describe the characteristics and outcomes of inpatients diagnosed with myocarditis complicated by heart block (HB) in a large national cohort. Methods We identified patients with primary ICD-9 codes for myocarditis HB from the Nationwide Inpatient Sample (NIS) Database from 1998 to 2013. We compared the baseline characteristics and compared clinical outcomes between patients with and without HB, and in patients with/without high degree atrioventricular block (HDAVB). Results From the NIS database, 31,760 patients had a principal diagnosis of myocarditis and HB was reported in 1.7% of these patients (n = 540). Female gender and Asian race were independently associated with HB. Out of 540 patients, 363 patients had HDAVB (67.2%) and 177 patients had not advanced HB (32.8%). Not advanced HB was not associated with an increased mortality rate compared to patients without HB (0% vs. 2.7%, p = 0.315). On the other hand, the incidence of cardiogenic shock, respiratory failure and renal failure were higher in patients with HDAVB (26.2% vs. 5.0%, 33.9% vs. 5.9% and 29.2% vs. 5.5%, p < 0.001 respectively). Patients with HDAVB required more procedural support (incidence of intra-aortic balloon pump 17.8% vs. 3.3%). They also had significantly longer lengths of hospital stay (9.4 +/- 9.4 vs. 4.3 +/- 8.4, p < 0.001) and higher mortality (15.5% vs. 2.7%, p < 0.001). Compared to myocarditis patients without HB, the odds for mortality in myocarditis patients with HDAVB 1.58 (95% CI = 1.03-2.49, p = 0.039). Conclusions The incidence of HB and HDAVB among patients with acute myocarditis was 1.7% and 1.1% respectively. Female gender and Asian race were both independently associated with significant odds for the occurrence of HB and HDAVB. High degree atrioventricular block was independently associated with increased morbidity and mortality.