Abstract 16491: Predictors of Incident Conduction System Disease in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT)

Introduction: Left and right bundle branch block (L and RBBB) have been associated with heightened morbidity and mortality, but risk factors for incident conduction disease remain unknown. Understanding factors that accelerate or delay conduction abnormalities could help identify therapies to treat or prevent this condition. Hypothesis: Clinical variables associated with myocardial fibrosis will increase conduction system disease risk while treatment with lisinopril (an anti-fibrotic) will reduce this risk. Methods: The Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial was a double-blind clinical trial that randomized 33,357 hypertensive participants ≥ 55 years of age with at least one other cardiovascular risk factor to treatment with amlodipine, lisinopril, or chlorthalidone. An electrocardigram (ECG) was obtained at study enrollment and at every two years of follow up. Conduction system disease was defined as LBBB, RBBB, intraventricular conduction delay, or 1st degree AV block. Participants without a baseline or follow up ECG (n=4,510) or with baseline conduction disease (n=6,181) were excluded. Cox proportional hazards models were used to examine predictors of incident disease. Results: Among 21,129 participants without prevalent conduction disease, 444 developed LBBB, 608 developed RBBB, and 1,138 developed any conduction defect during a mean 5.0 ± 1.2 years of follow up. Several factors were significantly associated with incident disease (Figure). Compared to chlorthalidone, lisinopril was associated with a significant 19% reduction in conduction abnormalities (HR 0.81, 95% CI 0.69-0.95). Conclusions: Incident conduction system disease is independently associated with multiple clinical factors and is significantly reduced by lisinopril therapy. Further studies are warranted to determine if pharmacologic treatment can impact conduction abnormality outcomes, including pacemaker implantation.