HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text Full Text (PDF) All Versions of this Article: 293/5/H3046    most recent 00728.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Johnson, L. Articles by Pinsky, M. R. Search for Related Content PubMed PubMed Citation Articles by Johnson, L. Articles by Pinsky, M. R.

Differential effects of left ventricular pacing sites in an acute canine model of contraction dyssynchrony

¹Cardiovascular Systems Laboratory, Department of Bioengineering, ²Cardiopulmonary Research Laboratory, Department of Critical Care Medicine, and ³Cardiovascular Institute, University of Pittsburgh, Pittsburgh, Pennsylvania

Submitted 21 June 2007 ; accepted in final form 12 September 2007

The goal of the present study was to assess the effects of left ventricular (LV) pacing sites (apex vs. free wall) on radial synchrony and global LV performance in a canine model of contraction dyssynchrony. Ultrasound tissue Doppler imaging and hemodynamic (LV pressure-volume) data were collected in seven anesthetized, opened-chest dogs. Right atrial (RA) pacing served as the control, and contraction dyssynchrony was created by simultaneous RA and right ventricular (RV) pacing to induce a left bundle-branch block-like contraction pattern. Cardiac resynchronization therapy (CRT) was implemented by adding simultaneous LV pacing to the RV pacing mode at either the LV apex (CRTa) or free wall (CRTf). A new index of synchrony was developed via pair-wise cross-correlation analysis of tissue Doppler radial strain from six midmyocardial cross-sectional regions, with a value of 15 indicating perfect synchrony. Compared with RA pacing, RV pacing significantly decreased radial synchrony (11.1 ± 0.8 vs. 4.8 ± 1.2, P < 0.01) and global LV performance (cardiac output: 2.0 ± 0.3 vs. 1.4 ± 0.1 l/min and stroke work: 137 ± 22 vs. 60 ± 14 mJ, P < 0.05). Although both CRTa and CRTf significantly improved radial synchrony, only CRTa markedly improved global function (cardiac output: 2.1 ± 0.2 l/min and stroke work: 113 ± 13 mJ, P < 0.01 vs. RV pacing). Furthermore, CRTa decreased LV end-systolic volume compared with RV pacing without any change in LV end-systolic pressure, indicating an augmented global LV contractile state. Thus, LV apical pacing appears to be a superior pacing site in the context of CRT. The dissociation between changes in synchrony and global LV performance with CRTf suggests that regional analysis from a single plane may not be sufficient to adequately characterize contraction synchrony.

cardiac resynchronization therapy; left ventricular global performance; myocardial strain; tissue Doppler imaging