Long PR Interval Leads to Atrial Remodeling, Fibrosis and Inducible Atrial Fibrillation in a Swine Model.

BACKGROUND

Pacing algorithms have been developed to minimize the risk of pacing-induced ventricular dysfunction at the expense of a prolonged PR interval. However, a long PR interval has been associated with incident atrial fibrillation (AF), and the impact of a prolonged PR interval on atrial remodeling remains unclear.

OBJECTIVES

This study investigated the impact of a prolonged PR interval on atrial remodeling in swine.

METHODS

In total, 24 Yucatan miniswine were divided into 3 groups: control (AAI 90 beats/min, n = 8), standard (160/180 ms, n = 8), and long (350 ms, n = 8) atrioventricular delay (AVD) groups. At baseline, all animals underwent electrophysiologic study and pacemaker implantation. Swine in the standard and long AVD groups underwent atrioventricular junction ablation following implantation of a dual-chamber pacemaker with left bundle branch area pacing leads. Atrial and left ventricular function were assessed by monthly speckle-tracking echocardiography. At 16 weeks, repeated electrophysiological studies and histological analysis were performed.

RESULTS

Baseline paced QRS durations after atrioventricular junction ablation (control, 76.8 ± 3.5 ms; standard, 77.1 ± 4.1 ms; long, 77.9 ± 3.8 ms; P = 0.835), left ventricular dyssynchrony (control, 7 [Q1-Q3: 0-11 ms]; standard, 7 [Q1-Q3: 0-10 ms]; long, 9 [Q1-Q3: 2-9 ms]; P = 0.986) and left ventricular ejection fraction (control, 81.1 ± 7.4%; standard, 85.9 ± 5.6%; long, 82.4 ± 7.4%; P = 0.373) did not differ among the groups. At 4 months, the long AVD group exhibited greater left atrial dyssynchrony (control, 25.8 ± 12.3 ms; standard, 23.6 ± 12.0 ms; long, 81.1 ± 19.5 ms; P < 0.001), decreased left atrial peak strain (control, 39.6 ± 4.5%; standard, 37.4 ± 5.3%; long, 22.3 ± 5.4%; P < 0.001), higher atrial fibrosis burden (control, 6.2 ± 1.0%; standard, 6.6 ± 0.6%; long, 10.6 ± 1.3%; P < 0.001) and greater AF inducibility (control, 0% [Q1-Q3: 0%-8%]; standard, 0% [Q1-Q3: 0%-0%]; long, 39% [Q1-Q3: 25%-64%]; P < 0.001) than the other groups.

CONCLUSIONS

A long AVD led to worse atrial function, inducible AF, and fibrosis in this model, demonstrating that a prolonged PR interval may promote atrial remodeling supporting the development of AF.