Prognostic Significance of Premature Atrial Complexes Burden in Prediction of Long-Term Outcome

Abstract

Background: The prognostic significance of premature atrial complex (PAC) burden is not fully elucidated. We aimed to investigate the relationship between the burden of PACs and long-term outcome.

Methods and results: We investigated the clinical characteristics of 5371 consecutive patients without atrial fibrillation (AF) or a permanent pacemaker (PPM) at baseline who underwent 24-hour electrocardiography monitoring between January 1, 2002, and December 31, 2004. Clinical event data were retrieved from the Bureau of National Health Insurance of Taiwan. During a mean follow-up duration of 10±1 years, there were 1209 deaths, 1166 cardiovascular-related hospitalizations, 3104 hospitalizations for any reason, 418 cases of new-onset AF, and 132 PPM implantations. The optimal cut-off of PAC burden for predicting mortality was 76 beats per day, with a sensitivity of 63.1% and a specificity of 63.5%. In multivariate analysis, a PAC burden >76 beats per day was an independent predictor of mortality (hazard ratio: 1.384, 95% CI: 1.230 to 1.558), cardiovascular hospitalization (hazard ratio: 1.284, 95% CI: 1.137 to 1.451), new-onset AF (hazard ratio: 1.757, 95% CI: 1.427 to 2.163), and PPM implantation (hazard ratio: 2.821, 95% CI: 1.898 to 4.192). Patients with frequent PAC had increased risk of mortality attributable to myocardial infarction, heart failure, and sudden cardiac death. Frequent PACs increased risk of PPM implantation owing to sick sinus syndrome, high-degree atrioventricular block, and/or AF.

Conclusions: The burden of PACs is independently associated with mortality, cardiovascular hospitalization, new-onset AF, and PPM implantation in the long term.

Keywords: atrial fibrillation; permanent pacemaker; premature atrial complex; sick sinus syndrome.

Figure 1

ROC curve survival analysis by PAC numbers. The optimal cut-off of PAC burden for predicting mortality was 76 beats per day (Youden index), with a sensitivity of 63.1% and specificity of 63.5%. AUC indicates area under the curve; PAC, premature atrial complex; ROC, receiver operator characteristic.

Figure 2

Impact of PAC burden on survival, CV hospitalization, new-onset AF, and PPM implantation. A, Patient survival of PAC ≤76 beats per day group compared with PAC >76 beats per day group (P<0.001 by log-rank test). B, Patient CV hospitalization-free survival of PAC ≤76 beats per day group compared with PAC >76 beats per day group (P<0.001 by log-rank test). C, Patient AF-free survival of PAC ≤76 beats per day group compared with PAC >76 beats per day group (P<0.001 by log-rank test). D, Patient PPM-free survival of PAC ≤76 beats per day group compared with PAC >76 beats per day group (P<0.001 by log-rank test). E, Patient survival of PAC burden in quartile comparison (P<0.001 by log-rank test). F, Patient CV hospitalization-free survival of PAC burden in quartile comparison (P<0.001 by log-rank test). G, Patient AF-free survival of PAC burden in quartile comparison (P<0.001 by log-rank test). H, Patient PPM-free survival of PAC burden in quartile comparison (P<0.001 by log-rank test). *P<0.05 in comparison with Quartile 1; ^†P<0.05 in comparison with Quartile 2; ^‡P<0.05 in comparison with Quartile 3. AF indicates atrial fibrillation; CV, cardiovascular; PAC, premature atrial complex; PPM, permanent pacemaker.

Figure 3

Forest plot for subgroup analysis for all-cause mortality. Hazard ratio of PAC >76 beats per day group compared with PAC ≤76 beats per day group in different subgroups of patients with individual risk factors. *P value for the PACs burden by each stratification variables interaction. CAD indicates coronary artery disease; DM, diabetes mellitus; HF, heart failure; HTN, hypertension; MI, myocardial infarction; PAC, premature atrial complex.