Impaired adaptation to left atrial pressure increase in patients with atrial fibrillation

Background or purpose Episodes of left atrial (LA) pressure increase predispose to atrial fibrillation (AF). The adaptation of LA mechanical function and electrophysiology to pressure elevation in healthy adults, and in patients with AF, is largely unknown. Methods Eleven patients with left-sided accessory pathway (controls) and 16 patients with paroxysmal AF undergoing catheter ablation were studied. LA pressure (LAP) was recorded through transseptal catheterization, while speckle tracking-derived peak LA longitudinal strain (PALS) was measured using transthoracic echocardiography. Stiffness index (SI) was calculated as mean LAP/PALS. Effective refractory period (ERP) of the LA was determined during simultaneous atrioventricular (AV) pacing and during atrial pacing. Results At baseline, AF patients had higher LA pressure (mean LAP 8.3 ± 4.7 vs. 5.1 ± 3.1 mmHg, p = 0.048), reduced LA mechanical function (PALS 15.1 ± 5.1 vs. 21.6 ± 6.2 %, p = 0.006, SI 0.69 ± 0.75 vs. 0.28 ± 0.22, p = 0.015), and longer LA ERP (242.3 ± 33.4 vs. 211.7 ± 15.6 ms, p = 0.017). Mean LAP was increased to the same extent by AV pacing in controls and AF patients (mean change 12.6 ± 7.4 vs. 12.6 ± 7.5 mmHg, p = 0.980). At the same time PALS decreased (from 15.1 ± 5.1 to 11.6 ± 3.3 %, p = 0.008), SI increased (from 0.69 ± 0.75 to 1.29 ± 1.17, p