title: The Effect of Right Ventricular Apical and Nonapical Pacing on the Short- and Long-Term Changes in Left Ventricular Ejection Fraction: A Systematic Review and Meta-Analysis of Randomized-Controlled Trials.
abstract: BACKGROUND
  The right ventricular apex (RVA) is the traditional lead site for chronic pacing but in some patients may cause impaired left ventricular (LV) systolic function over time. Comparisons with right ventricular nonapical (RVNA) pacing sites have generated inconsistent results and recent meta-analyses have demonstrated unclear benefit due to heterogeneity across studies.
  
  
  RESULTS
  A systematic search for randomized controlled trials that compared LV ejection fraction (LVEF) outcomes between RVNA and RVA pacing was performed up to October 2014. Twenty-four studies (n = 1,628 patients) met the inclusion criteria. To avoid between study heterogeneity two homogenous groups were created; group 1 where studies reported a difference (in favor of RVNA pacing) and group 2 where studies reported no difference between pacing sites. For group 1, weighted mean difference between RVNA and RVA pacing in terms of LVEF at follow-up was 5.40% (95% confidence interval [CI]: 3.94-6.87), related in part to group one's RVA arm demonstrating a significant reduction (mean loss -3.31%; 95% CI: -6.19 to -0.43) in LVEF between study baseline and end of follow-up. Neither of these finding were seen in group 2. Weighted regression modeling demonstrated that inclusion of poor baseline LVEF (<40%) in combination with greater than 12 months follow-up was three times more common in group 1 compared to group 2 (weighted relative risk 2.82; 95% CI: 1.03-7.72; P = 0.043).
  
  
  CONCLUSIONS
  In patients requiring chronic right ventricular pacing where there is inclusion of impaired baseline LVEF (<40%), RVA pacing is associated with deterioration in LV function relative to RVNA pacing.
authors.affiliation: From the Division of Epidemiology and Biostatistics, School of Public Health, The University of Queensland, Brisbane, Australia.
authors.forename: Mohammad Akhtar
authors.initials: MA
authors.lastname: Hussain
authors.affiliation: Research School of Population Health, The Australian National University, Canberra, Australia.
authors.forename: Luis
authors.initials: L
authors.lastname: Furuya-Kanamori
authors.affiliation: Department of Cardiology, Princess Alexandra Hospital, Brisbane, Australia.|University of Queensland Medical School, Brisbane, Australia.
authors.forename: Gerald
authors.initials: G
authors.lastname: Kaye
authors.affiliation: Cochrane Acute Respiratory Infections Group, Faculty of Health Sciences and Medicine, Bond University, Gold Coast, Australia.
authors.forename: Justin
authors.initials: J
authors.lastname: Clark
authors.affiliation: Research School of Population Health, The Australian National University, Canberra, Australia.
authors.forename: Suhail A R
authors.initials: SA
authors.lastname: Doi
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D058406:Cardiac Resynchronization Therapy / Q000379:methods* / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D015995:Prevalence; D016032:Randomized Controlled Trials as Topic; D018570:Risk Assessment; D013318:Stroke Volume; D016896:Treatment Outcome; D018487:Ventricular Dysfunction, Left / Q000175:diagnosis / Q000453:epidemiology* / Q000517:prevention & control*
keywords: LVEF; pacing site; randomized trial; right ventricular apical pacing; right ventricular nonapical pacing; septal