title: Functional abnormalities in patients with permanent right ventricular pacing: the effect of sites of electrical stimulation.
abstract: OBJECTIVE
  We sought to evaluate the long-term effects of alternative right ventricular pacing sites on myocardial function and perfusion.
  
  
  BACKGROUND
  Previous studies have demonstrated that asynchronous ventricular activation due to right ventricular apical (RVA) pacing alters regional myocardial perfusion and functions.
  
  
  METHODS
  We randomized 24 patients with complete atrioventricular block to undergo permanent ventricular stimulation either at the RVA (n = 12) or right ventricular outflow (RVOT) (n = 12). All patients underwent dipyridamole thallium myocardial scintigraphy and radionuclide ventriculography at 6 and 18 months after pacemaker implantation.
  
  
  RESULTS
  After pacing, the mean QRS duration was significantly longer during RVA pacing than during RVOT pacing (151 +/- 6 vs. 134 +/- 4 ms, p = 0.03). At six months, the incidence of myocardial perfusion defects (50% vs. 25%) and regional wall motion abnormalities (42% vs. 25%) and the left ventricular ejection fraction (LVEF) (55 +/- 3% vs. 55 +/- 1%) were similar during RVA pacing and RVOT pacing (p > 0.05). However, at 18 months, the incidence of myocardial perfusion defects (83% vs. 33%) and regional wall motion abnormalities (75% vs. 33%) were higher and LVEF (47 +/- 3 vs. 56 +/- 1%) was lower during RVA pacing than during RVOT pacing (all p < 0.05). Patients with RVA pacing had a significant increase in the incidence of myocardial perfusion defects (p < 0.05) and a decrease in LVEF (p < 0.01) between 6 and 18 months, but patients with RVOT pacing did not (p > 0.05).
  
  
  CONCLUSIONS
  This study demonstrates that preserved synchronous ventricular activation with RVOT pacing prevents the long-term deleterious effects of RVA pacing on myocardial perfusion and function in patients implanted with a permanent pacemaker.
authors.affiliation: Cardiology Division, Department of Medicine, University of Hong Kong, Hong Kong, China. hftse@hkucc.hku.hk
authors.forename: Hung Fat
authors.initials: HF
authors.lastname: Tse
authors.forename: Cannas
authors.initials: C
authors.lastname: Yu
authors.forename: Kwong Kuen
authors.initials: KK
authors.lastname: Wong
authors.forename: Vella
authors.initials: V
authors.lastname: Tsang
authors.forename: Yim Lung
authors.initials: YL
authors.lastname: Leung
authors.forename: Wai Yin
authors.initials: WY
authors.lastname: Ho
authors.forename: Chu Pak
authors.initials: CP
authors.lastname: Lau
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002304:Cardiac Pacing, Artificial; D003326:Coronary Circulation; D004176:Dipyridamole; D004562:Electrocardiography; D005260:Female; D006327:Heart Block / Q000000981:diagnostic imaging / Q000503:physiopathology* / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010138:Pacemaker, Artificial; D011446:Prospective Studies; D015635:Radionuclide Ventriculography; D013794:Thallium Radioisotopes; D015899:Tomography, Emission-Computed, Single-Photon; D014665:Vasodilator Agents
chemical_list: D013794:Thallium Radioisotopes; D014665:Vasodilator Agents; D004176:Dipyridamole