First-Degree Atrioventricular Block is Associated With Heart Failure and Death in Persons With Stabl
First-Degree Atrioventricular Block is Associated With Heart Failure and Death in Persons With Stable Coronary Artery Disease
Aims First-degree atrioventricular block (AVB) has traditionally been considered a benign electrocardiographic finding in healthy individuals. However, the clinical significance of first-degree AVB has not been evaluated in patients with stable coronary heart disease. We investigated whether first-degree AVB is associated with heart failure (HF) and mortality in a prospective cohort study of outpatients with stable coronary artery disease (CAD).
Methods and results We measured the P–R interval in 938 patients with stable CAD and classified them into those with (P–R interval ≥220 ms) and without (P–R interval <220 ms) first-degree AVB. Hazard ratios (HRs) and 95% confidence intervals were calculated for HF hospitalization and all-cause mortality. During 5 years of follow-up, there were 123 hospitalizations for HF and 285 deaths. Compared with patients who had normal atrioventricular conduction, those with first-degree AVB were at increased risk for HF hospitalization (age-adjusted HR 2.33: 95% CI 1.49–3.65; P= 0.0002), mortality [age-adjusted HR 1.58; 95% CI (1.13–2.20); P = 0.008], cardiovascular (CV) mortality [age-adjusted HR 2.33; 95% CI (1.28–4.22); P= 0.005], and the combined endpoint of HF hospitalization or CV mortality (age-adjusted HR 2.43: 95% CI 1.64–3.61; P ≤ 0.0001). These associations persisted after multivariable adjustment for heart rate, medication use, ischaemic burden, and QRS duration. Adjustment for left ventricular systolic and diastolic function partially attenuated the effect, but first-degree AVB remained associated with the combined endpoint of HF or CV death (HR 1.61, CI 1.02–2.54; P= 0.04).
Conclusion In a large cohort of patients with stable coronary artery disease, first-degree AVB is associated with HF and death.
The P–R interval measures the time from the onset of atrial depolarization to the onset of ventricular depolarization. This interval sums the time taken for the sequential conduction of electrical impulses from the sino-atrial node through the atrium, atrioventricular (AV) node, His Bundle, and early fascicular system until the initiation of septal depolarization. Consequently, there are numerous potential causes of P–R prolongation including intra-atrial conduction defects, increased vagal tone leading to increased AV nodal delay, conduction disease in the AV node, conduction disease in the His-Bundle, and the presence of anti-arrhythmic medications.
Prior studies have indicated that first-degree atrioventricular block (AVB) is a benign finding with no prognostic significance in healthy patients at low risk for cardiovascular events. However, a growing body of literature has emerged that challenges our established conceptions of apparently 'benign' echocardiogram (ECG) findings such as right bundle branch block, repolarization abnormalities, and T-wave morphology. Notably, a P–R interval >300 ms and sudden increases in AV delay have been proposed as a cause of heart failure (HF) symptoms. Accordingly, symptoms or haemodynamic abnormalities attributable to first degree AVB have been accepted by the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society as indications for permanent pacemaker implantation. Furthermore, the demographic trend of population ageing is likely to increase the prevalence of abnormal ECGs and the incidence of cardiovascular events.
Recently, the Framingham group reported that first-degree AVB portended an increased risk for atrial fibrillation, pacemaker implantation, and all-cause mortality among community-dwelling adults. However, the prognostic effects of AVB have not been evaluated in patients with established coronary artery disease (CAD). Therefore, we tested the hypothesis that first-degree AVB is associated with HF, cardiovascular (CV) mortality, and all-cause mortality in a prospective cohort study of patients with stable CAD.
Abstract and Introduction
Abstract
Aims First-degree atrioventricular block (AVB) has traditionally been considered a benign electrocardiographic finding in healthy individuals. However, the clinical significance of first-degree AVB has not been evaluated in patients with stable coronary heart disease. We investigated whether first-degree AVB is associated with heart failure (HF) and mortality in a prospective cohort study of outpatients with stable coronary artery disease (CAD).
Methods and results We measured the P–R interval in 938 patients with stable CAD and classified them into those with (P–R interval ≥220 ms) and without (P–R interval <220 ms) first-degree AVB. Hazard ratios (HRs) and 95% confidence intervals were calculated for HF hospitalization and all-cause mortality. During 5 years of follow-up, there were 123 hospitalizations for HF and 285 deaths. Compared with patients who had normal atrioventricular conduction, those with first-degree AVB were at increased risk for HF hospitalization (age-adjusted HR 2.33: 95% CI 1.49–3.65; P= 0.0002), mortality [age-adjusted HR 1.58; 95% CI (1.13–2.20); P = 0.008], cardiovascular (CV) mortality [age-adjusted HR 2.33; 95% CI (1.28–4.22); P= 0.005], and the combined endpoint of HF hospitalization or CV mortality (age-adjusted HR 2.43: 95% CI 1.64–3.61; P ≤ 0.0001). These associations persisted after multivariable adjustment for heart rate, medication use, ischaemic burden, and QRS duration. Adjustment for left ventricular systolic and diastolic function partially attenuated the effect, but first-degree AVB remained associated with the combined endpoint of HF or CV death (HR 1.61, CI 1.02–2.54; P= 0.04).
Conclusion In a large cohort of patients with stable coronary artery disease, first-degree AVB is associated with HF and death.
Introduction
The P–R interval measures the time from the onset of atrial depolarization to the onset of ventricular depolarization. This interval sums the time taken for the sequential conduction of electrical impulses from the sino-atrial node through the atrium, atrioventricular (AV) node, His Bundle, and early fascicular system until the initiation of septal depolarization. Consequently, there are numerous potential causes of P–R prolongation including intra-atrial conduction defects, increased vagal tone leading to increased AV nodal delay, conduction disease in the AV node, conduction disease in the His-Bundle, and the presence of anti-arrhythmic medications.
Prior studies have indicated that first-degree atrioventricular block (AVB) is a benign finding with no prognostic significance in healthy patients at low risk for cardiovascular events. However, a growing body of literature has emerged that challenges our established conceptions of apparently 'benign' echocardiogram (ECG) findings such as right bundle branch block, repolarization abnormalities, and T-wave morphology. Notably, a P–R interval >300 ms and sudden increases in AV delay have been proposed as a cause of heart failure (HF) symptoms. Accordingly, symptoms or haemodynamic abnormalities attributable to first degree AVB have been accepted by the American College of Cardiology, the American Heart Association, and the Heart Rhythm Society as indications for permanent pacemaker implantation. Furthermore, the demographic trend of population ageing is likely to increase the prevalence of abnormal ECGs and the incidence of cardiovascular events.
Recently, the Framingham group reported that first-degree AVB portended an increased risk for atrial fibrillation, pacemaker implantation, and all-cause mortality among community-dwelling adults. However, the prognostic effects of AVB have not been evaluated in patients with established coronary artery disease (CAD). Therefore, we tested the hypothesis that first-degree AVB is associated with HF, cardiovascular (CV) mortality, and all-cause mortality in a prospective cohort study of patients with stable CAD.
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