Heart Failure Due to High-Degree Atrioventricular Block: How Frequent Is It and What Is the Cause?

Background: The causes of heart failure (HF) during high-grade atrioventricular block (AVB) are poorly understood. This study assessed the mechanisms of HF in patients with AVB. Methods: We studied patients presenting (between 2012 and 2016) with high-grade AVB not related to acute myocardial infarction. Patients with preexisting significant valvular heart disease were excluded. All patients underwent comprehensive echocardiographic evaluation during AVB, before pacemaker implantation. The diagnosis of HF was based on the Framingham criteria. Results: A total of 122 patients were included in the study, 50% male, average age 76 ± 13 years. Twenty-eight patients (23%) with AVB presented with HF. Univariate correlates associated with HF were decrease in cardiac output (CO) (odds ratio [OR] 0.68 [95% confidence interval 0.49-0.9] per L/min; P = 0.007), measures of impaired left ventricular (LV) compliance, and increase in diastolic mitral regurgitation (MR) volume (OR 1.04 [1.01-1.07] per cc; P = 0.0016). Ventricular rate during AVB and LV ejection fraction were not significantly associated with the presence of HF. By multivariate nominal logistic analysis, the best model associated with HF included diastolic MR volume (OR 1.04 [1.001-1.09]; P = 0.02), A-wave deceleration time (OR 0.96 [0.94-0.9]; P = 0.001), and CO (OR 0.92 [0.4-1.00]; P = 0.005) (χ² = 30.6; area under the receiver operating characteristic curve = 0.84; P < 0.0001 for the entire model). Conclusions: In the setting of high-degree AVB, clinical HF occurrence correlates with impaired LV compliance and diastolic MR volume, but not with heart rate or LV ejection fraction. The cardiac performance of patients with poor LV compliance and high-volume diastolic MR may show maladjustment to slow heart rates, manifesting as low CO and HF.