NEW APPROACH TO OLD CONCEPTS: PROGNOSIS AND NATURAL HISTORY OF CONDUCTION SYSTEM DISEASE; PROGNOSTIC IMPLICATIONS OF CONDUCTION SYSTEM DISEASE

Abstract

Conduction abnormalities are commonly identified in approximately 10% of patients on standard 12-lead electrocardiograms (ECGs). While there have been previous attempts at characterizing the prognostic implications of these findings, the association between intraventricular conduction delays (IVCD) and outcomes are still poorly understood. We performed a retrospective cohort study of patients enrolled in the APPROACH registry. We included patients who had an ECG recorded in the MUSE database in the 180 days before coronary angiography or within 3 subsequent days. We excluded patients with reduced left ventricular ejection fraction (LVEF), paced rhythms, and those who died the day of coronary angiography. We used multivariable Cox proportional hazards models to assess associations between IVCD and all-cause mortality after correcting for age, sex, medical co-morbidities, LVEF and extent of coronary artery disease. We modeled conduction system disease as a baseline and as a time-varying exposure. We identified 11,267 patients (mean age 62.3 +/- 12.4, 70.1% male) who underwent coronary angiography between May 2006 and March 2014, 10,227 (90.8%) of whom presented with ACS. Over a median follow-up of 3.6 years, 922 (8.2%) patients died. IVCD was identified in 2,738 (24.3%) patients at baseline. After adjusting for all baseline factors, right bundle branch block (adjusted HR 1.41, 95% CI 1.15-1.72, p < 0.01) and non-specific intraventricular conduction delay (adjusted HR 1.60, 95% CI 1.24-2.06, p < 0.01) were independently associated with increased all-cause mortality. However, after similar adjustments left bundle branch block (Adjusted HR 0.79, 95% CI 0.61-1.02, p=0.07) was not associated with all-cause mortality. Our results were similar when modeling conduction disease as a baseline feature and as a time-varying exposure. After correction for medical co-morbidities and extent of coronary artery disease, right bundle branch block and non-specific intraventricular conduction delay is associated with increased all-cause mortality. However, in contrast to earlier studies, we found no association with left bundle branch block.