title: Acute effects of right ventricular apical pacing on left atrial remodeling and function.
abstract: 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.
authors.affiliation: Institute of Vascular Medicine and Division of Cardiology, Prince of Wales Hospital, The Chinese University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Jun-Min
authors.initials: JM
authors.lastname: Xie
authors.forename: Fang
authors.initials: F
authors.lastname: Fang
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhang
authors.forename: John E
authors.initials: JE
authors.lastname: Sanderson
authors.forename: Joseph Yat-Sun
authors.initials: JY
authors.lastname: Chan
authors.forename: Yat-Yin
authors.initials: YY
authors.lastname: Lam
authors.forename: Cheuk-Man
authors.initials: CM
authors.lastname: Yu
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial; D005260:Female; D006325:Heart Atria / Q000000981:diagnostic imaging*; D006352:Heart Ventricles; D006801:Humans; D008297:Male; D008875:Middle Aged; D009929:Organ Size; D016896:Treatment Outcome; D014463:Ultrasonography; D018487:Ventricular Dysfunction, Left / Q000000981:diagnostic imaging* / Q000517:prevention & control*