Abstract 18179: Predictors of Incident Pacemaker Implantation in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT)

Introduction: Although permanent pacemaker (PPM) implantation is common, predictors of this procedure have not been well studied. We therefore sought to identify characteristics that predict PPM implantation in the ALLHAT trial. In addition, given the known mechanistic links between hypertension, inflammation, fibrosis, and conduction abnormalities, we examined whether randomized assignment to antihypertensive therapy might affect PPM implantation. Hypothesis: Lisinopril, given its proposed anti-fibrotic effects, will reduce the risk of PPM implantation. Methods: ALLHAT was a double-blind clinical trial that randomized hypertensive participants ≥55 years old with at least one other cardiovascular risk factor to treatment with amlodipine, lisinopril, or chlorthalidone. The primary outcome of the present analysis was PPM implantation for sinus node dysfunction or AV block. A secondary analysis examined predictors of PPM implantation for complete heart block (CHB). Participants who received a PPM during a catheter ablation procedure or for an atrial arrhythmia were censored at implant. Results: Among 21,480 participants, 183 underwent PPM implantation (47 for CHB) during a mean 4.8 ± 1.6 years of follow up. Several factors were significantly associated with PPM implantation ( Figure ). Randomization to lisinopril (versus chlorthalidone) was not associated with a reduced risk of overall PPM implantation or PPM implantation for CHB. Amlodipine treatment similarly did not reduce overall PPM risk but did result in a reduced risk of PPM implantation for CHB (HR 0.40, 95% CI 0.16-0.97, p=0.04). Conclusions: PPM implantation is independently associated with multiple clinical factors but is not reduced by lisinopril. The mechanisms through which amlodipine might reduce PPM implantation for CHB are not known.