BACKGROUND: The long term prognosis of an incidental finding of delayed intraventricular conduction (DIVC) in individuals free of Ischemic Heart Disease (IHD) is controversial. DIVC may present electrocardiographically in the form of either left or right Complete Bundle Branch Block (CBBB), Incomplete Bundle Branch Block (IBBB) or Nonspecific Intraventricular Conduction Defect (NIVCD).
OBJECTIVE: To assess the long term prognostic significance of an incidental DIVC finding in a historical cohort followed-up for three decades
PATIENTS AND METHODS: A randomized stratified cohort of the adult Israel Jewish population, sampled from the National Population Registry (NPR), was followed from 1969. Medical examinations, ECGs and laboratory tests were performed in 1976-1982. Patients with IHD were excluded from the study. Remaining patients were divided to 3 groups: Free of DIVC, CBBB & NIVCD and IBBB. Vital status and date of death were updated until 02/2012 using the NPR. Multivariate survival analysis was performed, adjusting for demographic, clinical and electrocardiographic variables.
RESULTS: Of 2,465 subjects, 2,385 (96.8%) were free of DIVC, 42 (1.7%) presented with CBBB & NIVCD and 38 (1.5%) with IBBB. Variables significantly associated with DIVC were gender, blood pressure, abnormal QRS axis and PR interval duration. Median follow-up period was 30.4 years. Overall, 1,292 (52.4%) subjects died during follow-up. Compared to free of DIVC, all-cause mortality (ACM) rates of 66.7% and 57.9% were observed among CBBB & NIVCD and IBBB, (p=0.04 and p=0.43), respectively. Controlling for potential confounders, the incidental ECG finding was not a significant predictor for ACM: HR=0.86 (95%CI: 0.59-1.25), for CBBB & NIVCD, and HR=1.01 (95%CI: 0.66-1.55), for IBBB. Significant predictors for ACM were age, gender, origin, smoking, blood pressure, glucose levels and BMI.
CONCLUSION: DIVC in individuals free of IHD was not found to be an independent risk factor for long term ACM in this cohort study.
