Abstract 21137: Biventricular Borderzone Pacing to Prevent Post-Myocardial Infarction Adverse Remodeling
Introduction: Left ventricular (LV) dilatation following myocardial infarction is a precursor of the development of heart failure. Borderzone pacing produces peri-infarct pre-excitation which is hypothesized to unload the infarct in the short-term and prevent dilatation in the long-term.
Methods: Micro Yucatan swine (n=18) underwent 90-minute left anterior descending artery occlusion and recovery. Animals were assigned to either biventricular pacing with an LV lead in the antero-lateral borderzone with atrial-tracking pacing at an atrioventricular interval of 70% intrinsic, or control arm with no pacing. Animals were followed for 10 weeks. Anesthetized echocardiography was performed 1 week prior to infarct, and at 1, 4, and 10 weeks, with pacing-on in the therapy arm and pacing-off in the control arm.
Results: Five animals in each arm survived to ten weeks. QRS interval increased in all animals. In the therapy arm both end-diastolic (EDV) and end-systolic (ESV) volumes increased at 1 week then decreased toward baseline by 10 weeks (EDV 11.3±27.5%, p=0.41; ESV 66.4±47.7 %, p=0.017). In contrast, the control group volumes progressively increased to 10 weeks compared to baseline (EDV 89.6±74.3%, p=0.054; ESV 205.2±117.1 %, p=0.017) and compared to the therapy group at 10 weeks (EDV p=0.032, ESV p=0.032). Ejection fraction decreased equally in both arms, from 56.9±3.8% to 35.9±6.0% in the therapy arm and from 60.2±7.6% to 39.6±6.0 in the control arm. Interventricular septal thickening was preserved in the therapy arm and declined in the control arm.
Conclusions: The time course of LV volumes with therapy shows a positive effect of borderzone pacing. Regional myocardial function near the infarct was preserved with therapy as compared to control. The acute increase in LV volumes at week 1 in the therapy arm suggests short-term unloading of the infarct which may be globally transiently disadvantageous, progressing to an advantageous effect in the long-term.
- © 2010 by American Heart Association, Inc.