title: The immediate effects of pacemaker-related electric remodelling on left ventricular function in patients with sick sinus syndrome.
abstract: OBJECTIVE
  The immediate effects of electric remodelling on the left ventricular (LV) function by dual-chamber pacemakers remain unknown. The purpose of our study was to assess the interaction between heart rates and right ventricular pacing (VP) on LV contractility and diastolic function.
  
  
  RESULTS
  Twenty-five patients with dual-chamber pacemakers and sick sinus syndrome were evaluated. Echocardiographic examinations included standard and tissue-Doppler echocardiography at bilateral mitral annulus margins under either the intrinsic atrio-ventricular sequential conduction (ventricular sensing; VS) mode or right ventricular apical pacing (VP) mode. Under either mode, we accelerated the pacing rate at an increment of 15 b.p.m. step-by-step from 60 to 90/min. The tissue-Doppler echocardiography of mitral annulus showed that under the VS status, accelerating atrial pacing rate from 60 to 90 b.p.m. enhanced A'-wave velocity (P < or =0.002), whereas no significant change of LV ejection fraction (LVEF) and E'-wave velocity were noted. Under the VP status, acceleration of pacing rates exerted no effect on the LVEF, E'-, and A'-wave (P = NS). While shifting the pacemaker mode from VS to VP, the E'-wave velocity (P < or =0.002) and E'/A' ratio decreased significantly (P < or = 0.001). The A'-wave velocity also increased significantly during shifting to VP mode at 60 b.p.m. (P < or =0.004).
  
  
  CONCLUSIONS
  At fixed pacing rates, shifting from VS to VP mode impaired LV diastolic function immediately with preserved LV contractility. The acceleration of heart rate impaired LV diastolic function under VS mode.
authors.affiliation: Division of Cardiology, Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan.
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Wang
authors.forename: Yen-Hung
authors.initials: YH
authors.lastname: Lin
authors.forename: Yen-Bin
authors.initials: YB
authors.lastname: Liu
authors.forename: Jen-Kuang
authors.initials: JK
authors.lastname: Lee
authors.forename: Ying-Shren
authors.initials: YS
authors.lastname: Chen
authors.forename: Hsiu-Hao
authors.initials: HH
authors.lastname: Lee
authors.forename: Lung-Chun
authors.initials: LC
authors.lastname: Lin
authors.forename: Yi-Lwun
authors.initials: YL
authors.lastname: Ho
authors.forename: Wen-Jone
authors.initials: WJ
authors.lastname: Chen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012804:Sick Sinus Syndrome / Q000150:complications* / Q000175:diagnosis / Q000517:prevention & control*; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis* / Q000209:etiology*