Frequency and Significance of High-Degree Atrioventricular Block and Sinoatrial Node Dysfunction in Patients With Non-ST-Elevation Myocardial Infarction.

Characteristics of conduction disorders after ST-elevation myocardial infarction (STEMI) have been well described. In contrast, limited data are available on the incidence, treatment trends, and prognostic impact of conduction disorders after non-ST-elevation myocardial infarction (NSTEMI). Using the National Inpatient Sample database, we compared the characteristics and outcomes of conduction disorders in patients with a primary diagnosis of STEMI versus NSTEMI between 2010 and 2014. Conduction disorders were classified into‬ high-degree AV block (HDAVB), consisting of complete AV block or Mobitz type II second-degree AV block, and sinoatrial node dysfunction (SND). We identified 135,468 STEMI patients and 281,928 NSTEMI patients. In contrast to the STEMI cohort where HDAVB was more common than SND (2.4% vs 0.5%), SND was observed more often in the NSTEMI cohort, presenting in 2,417 patients (0.9%), followed by HDAVB in 1,745 patients (0.6%). In patients who developed HDAVB, NSTEMI patients were more likely to undergo permanent pacemaker implantation than STEMI patients (30.0% vs 11.6%; p < 0.001). The rate of permanent pacemaker implantation for SND was comparable between STEMI and NSTEMI patients (33.9% vs 30.5%; p = 0.10). In the NSTEMI cohort, patients who developed HDAVB had higher in-hospital mortality than those without any major conduction disorders (16.6% vs 3.8%; p < 0.001). In conclusion, SND was more common than HDAVB in the NSTEMI cohort, in contrast to the predominance of HDAVB observed in the STEMI cohort. About one-third of patients who developed HDAVB after NSTEMI underwent pacemaker implantation, suggesting lower rates of spontaneous resolution of HDAVB, when compared with STEMI patients.