Acute Effects of Right Ventricular Apical Pacing on Left Atrial Remodeling and Function.

Background : The acute effects of right ventricular apical (RVA) pacing on left atrial (LA) function in patients with normal ejection fraction are not clear. Methods : A total of 94 patients (age 68.1 ± 11.1 years, 26 men) with implanted RVA-based dual-chamber pacemakers were recruited into this study. Patients who were pacemaker-dependent, in persistent atrial fibrillation or left ventricular ejection fraction <45% were excluded. Echocardiography (iE33, Philips, Andover, MA, USA) was performed during intrinsic ventricular conduction (V-sense) and RVA pacing (V-pace) with 15 minutes between switching modes. The total maximal LA volume (LAV_max), preatrial contraction volume (LAV_pre), and minimal volume (LAV_min) were assessed by area-length method. Peak systolic, early diastolic, and peak late diastolic (atrial contractile) velocity (Sm-la, Em-la, and Am-la) and strain (ɛs-la, ɛe-la, and ɛa-la) were measured by color-coded tissue Doppler imaging (TDI) in four mid-LA walls at apical four- and two-chamber views. Results : During V-pace, LA volumes increased significantly compared with V-sense (LAV_max: 52.0 ± 18.8 vs 55.2 ± 21.1 mL, P = 0.005; LAV_pre: 39.8 ± 16.4 vs 41.3 ± 16.6 mL, P = 0.014; LAV_min: 27.4 ± 14.0 vs 29.1 ± 15.1 mL, P = 0.001). TDI parameters showed significant reduction in Sm-la and Em-la. Furthermore, ɛs-la, ɛe-la, and ɛa-la decreased significantly, especially in patients with preexisting diastolic dysfunction (all P < 0.01). Conclusions: RVA pacing acutely induced LA enlargement and impaired atrial contractility. Patients with preexisting diastolic dysfunction may be more vulnerable to develop LA dysfunction and remodeling after acute RVA pacing. (PACE 2011;XX:1-7) [ABSTRACT FROM AUTHOR]