Pacemaker Detected Prolonged Atrial High Rate Episodes – Incidence, Predictors And Implications; A Retrospective Observational Study

Introduction: Atrial tachyarrhythmias especially atrial fibrillation are the most commonly encountered arrhythmias in clinical practice. Most atrial tachyarrhythmia episodes are subclinical. Cardiac implantable electronic devices with atrial sensing function enable detection of atrial tachyarrhythmias through means of atrial high rate event algorithms. Prolonged atrial high rate episodes(AHRE) above a defined rate and duration threshold represent episodes of atrial fibrillation, atrial flutter, and longer atrial tachycardias that correlate strongly with risk for thromboembolic events. Objective: 1. To examine the occurrence of prolonged AHRE in dual-chamber pacemaker recipients over the study period. 2. To examine the factors which influence the occurrence of prolonged AHRE in these patients. Methods: In this study, we analyzed data of 398 patients without valvular heart disease or history of atrial fibrillation who underwent dual chamber permanent pacemaker implantation at our center from January 2013 to June 2018. Patient demographics, cardiovascular co-morbidities, medications, echocardiographic parameters such as ejection fraction and left atrial(LA) dimension were obtained. Also, we collected pacing characteristics such as paced QRS duration(QRSd), ventricular pacing site and cumulative percentage ventricular paced beats. Results: Prolonged AHRE occurred in 59 patients(14.8%). Baseline LA dimension was greater in patients with prolonged AHRE(median 35 mm, IQR 33e37 vs median 35 mm, IQR 34e38, P ¼ 0.004) compared to those without. Paced QRSd was significantly longer in patients with prolonged AHRE (median of 147 ms, IQR 139e160 ms vs 140 ms, IQR 132e150 ms; P < 0.001). On multivariable logistic regression, paced QRSd(OR 1.04, 95%CI 1.02e1.06; P ¼ 0.001) and baseline LA dimension(OR 1.14, 95%CI 1.03e1.27; P ¼ 0.01) significantly co-predicted AHRE. On Kaplan Meier analysis, patients with paced QRSd≥142 ms had more likelihood of developing prolonged AHRE during follow up (HR 2.46, CI 1.40e4.3, P ¼ 0.001). After adjusting for baseline values, patients with paced QRSd≥142 ms had significant decline in left ventricular ejection fraction (adjusted mean difference ¡1.27%; P ¼ 0.02) and significant LA dilation (adjusted mean difference 0.62 mm; P ¼ 0.05) Q1 Conclusion: In our study, paced QRSd and LA dimension were the strongest predictors for prolonged AHRE. The incidence of AHRE may be reduced by achieving the narrowest possible paced QRSd during device implantation.