740-1 Septal Pacing Improves Single Chamber-paced Left Ventricular Function: A Comparative Evaluation with Atrial and Apical Pacing

Right (R) ventricular (V) apical (Ap) pacing (P) alters left (L) V contraction compared to normal and may predispose to decreased LVfunction. RV septal (Sp) P maintains more normalized V depolarization and contraction patterns to improve paced LV hemodynamics and may be better suited as an electrode implant site. To evaluate efforts of pacing site on paced LV function in young hearts without coronary artery disease or intrinsic LV dysfunction. 17 patients (pts) (age 1–17 y, median 10) with normal cardiac anatomy underwent comparative LV hemodynamic evaluations during electrophysiologic studies. In each pt, LV function was assessed by measurement of LV end-diastolic pressure (p) (EDp), mean aortic (Ao) p (mmHg), LV dp/dt (mmHg/sec), Vmax (circ/sec), and Vpm (eire/sec) during sinus rhythm and after 20min of P each from R atrium (A), RV Ap and RV Sp at 150 ppm to mimic exercise. Optimal Sp P site was confirmed by recording a His bundle potential from the transvenous P catheter placed across the septal-tricuspid valve annulus.Results (mean ± sem)Sp P showed no significant differences from sinus or atrial P values. RV Ap P showed significantly worse LV function compared with Sp P.:HRdp/dtVmaxVpmLVEDpAopSinus951719±53824±0.926±15.2±0890±4RAP1501945±15224±0824±034.4±0.594±4RVSp P1501655±39920±072.7±15.9±0.989±4RVAp P1501482±373#1.7±0.1#2.0±0.6#8.7±14#82±4#P<0.05 compared with sinus, RAP and Sp PvaluesConclusionRV Sp P normalizes and significantly improves paced LV function over RV Ap P. In spite of loss of AV synchrony, LV function is comparable to sinus and RAP in pts without inherent myocardial dysfunction. This improvement in paced LV hemodynamics should be considered for any age pt requiring chronic single or dual chamber V P