Atrial Effective Refractory Periods in Patients With Frequent Premature Atrial Complexes: Implications for Atrial...

Recent animal models show that frequent premature atrial complexes (PACs) induce atrial remodeling through conduction slowing without altering the atrial effective refractory period (AERP), suggesting a mechanism distinct from atrial fibrillation (AF)-induced remodeling. However, the impact of frequent PACs on human AERP remains unclear.

The purpose of this study was to compare AERP characteristics in patients with isolated frequent PACs and those with AF.

This prospective study included patients undergoing ablation for isolated frequent PACs, paroxysmal atrial fibrillation (PAF), or persistent AF. After a 6-beat 600-ms drive train (S1), the S2 interval was increased in 10-ms steps until atrial capture occurred; the longest noncapturing S2 was defined as AERP. AERPs were measured at 9 sites, including 4 pulmonary veins (PVs), and 5 extra-PV regions. Interatrial conduction time was measured from P-wave onset to latest activation on the coronary sinus catheter.

A total of 143 patients were included (PAC: n = 21, burden 36 ± 17%; PAF: n = 65; persistent AF: n = 57). In the PVs, AERP was longest in PAC, intermediate in PAF, and shortest in persistent AF (PAC: 254.9 ± 22.4 vs PAF: 229.5 ± 38.6 vs persistent AF: 205.4 ± 29.1 ms; P < 0.001). In extra-PV regions, AERPs were similar between PAC and PAF, whereas persistent AF showed significantly shorter values (256.0 ± 21.7 vs 260.9 ± 28.2 vs 225.7 ± 24.2ms; P < 0.001). Interatrial conduction time was comparable between PAC and PAF but prolonged in persistent AF (122 ± 12 vs 118 ± 20 vs 131 ± 23 ms; P = 0.004). Multivariable regression demonstrated arrhythmia type as an independent determinant of both PV and extra-PV AERP (standardized β = -0.54 and -0.62, respectively; P < 0.001). Within PAC patients, AERPs did not differ by PAC origin.

Isolated frequent PACs were characterized by preserved AERP in both PV and extra-PV regions. Shorter AERPs in the PVs in PAF and more widespread AERP shortening in persistent AF may reflect the transition from PACs to PAF and then progression to persistent AF.