title: Evaluation of myocardial performance with conventional single-site ventricular pacing and biventricular pacing in a canine model of atrioventricular block.
abstract: BACKGROUND
  The aim of this study was to evaluate epicardial biventricular pacing as a means of maintaining synchronous ventricular activation in an acute canine model of AV block with normal ventricular anatomy and function. Chronic single-site ventricular pacing results in dyssynchronous ventricular activation and may contribute to ventricular dysfunction. Biventricular pacing has been used successfully in adult patients with congestive heart failure.
  
  
  RESULTS
  This was an acute study of open chest mongrel dogs (n = 13). ECG, left ventricular (LV), aortic, and pulmonary arterial pressures were measured. LV impedance catheters were used to assess cardiodynamics using instantaneous LV pressure-volume relations (PVR). Following radiofrequency ablation of the AV node, a temporary pacemaker was programmed 10 beats/min above the intrinsic atrial rate, with an AV interval similar to the baseline intrinsic PR interval. The pacing protocol consisted of 5-minute intervals with the following lead configurations: right atrium-right ventricular apex (RA-RVA), RA-LV apex (LVA), and RA-biventricular using combinations of four ventricular sites (RVA, RV outflow tract [RVOT], LVA, LV base [LVB]). RA-RVA was used as the experimental control. LV systolic mechanics, as measured by the slope of the end-systolic (Ees) PVR (ESPVR, mmHg/cc), was statistically greater (P < 0.05) with all modes of biventricular pacing (RA-RVA/LVA 20.0 +/- 2.9, RA-RVA/LVB 18.4 +/- 2.9, RA-RVOT/LVA 15.1 +/- 1.8, RA-RVOT/LVB 17.6 +/- 2.9) compared to single-site ventricular pacing (RA-RVA 12.8 +/- 1.6). Concurrent with this improvement in myocardial performance was a shortening of the QRS duration (RA-RVA 97.7 +/- 2.9 vs RA-RVA/LVA 75.7 +/- 4.9, RA-RVA/LVB 70.3 +/- 4.9, RA-RVOT/LVA 65.3 +/- 4.4, and RA-RVOT/LVB 76.7 +/- 5.9, P < 0.05).
  
  
  CONCLUSIONS
  In this acute canine model of AV block, QRS duration shortened and LV performance improved with epicardial biventricular pacing compared to standard single-site ventricular pacing.
authors.affiliation: Sibley Heart Center Cardiology, Children's Healthcare of Atlanta, Emory University School of Medicine, 52 Executive Park South, Suite 5200, Atlanta, GA 30329, USA. friasp@kidsheart.com
authors.forename: Patricio A
authors.initials: PA
authors.lastname: Frias
authors.forename: Joel S
authors.initials: JS
authors.lastname: Corvera
authors.forename: Laura
authors.initials: L
authors.lastname: Schmarkey
authors.forename: Margaret
authors.initials: M
authors.lastname: Strieper
authors.forename: Robert M
authors.initials: RM
authors.lastname: Campbell
authors.forename: Jakob
authors.initials: J
authors.lastname: Vinten-Johansen
mesh_terms: D000818:Animals; D001011:Aorta / Q000503:physiopathology; D001810:Blood Volume; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D017115:Catheter Ablation; D004285:Dogs; D004562:Electrocardiography; D006321:Heart / Q000503:physiopathology*; D006327:Heart Block / Q000503:physiopathology* / Q000601:surgery; D011312:Pressure; D011651:Pulmonary Artery / Q000503:physiopathology; D013997:Time Factors; D016277:Ventricular Function, Left