752-3 Evaluation of Regional Myocardial Perfusion in Early Pacing-induced Left Ventricular Dysfunction Using Myocardial Contrast Echocardiography

Sustained rapid left ventricular (LV) pacing has been used to induce congestive heart failure, but whether regional myocardial perfusion contributes to the development of myocardial dysfunction is unknown. Therefore, we examined 4 pigs before and sequentially during sustained rapid LV pacing (225 bpm) from the at posterolateral epicardium. We performed myocardial contrast echocardiography (MCE) with left atrial injection of an investigational galactose contrast agent prior to pacing and daily for 4 days after onset of pacing. Pacemakers were inactivated for 60 min prior to data acquisition. The ratio of peak intensity after injection and baseline intensity of region of interest (peak intensity ratio) was measured at 8 segments (Fig) in the short axis view at the tip of papillary muscle using video intensitometry. Percent wall thickening (%WTh) in the interventricular septum (IVS) and posterolateral wall (PLW) were assessed by M-mode echo. Over the 4 days of pacing, the peak intensity ratio progressively decreased in the PLW [region 4 (p l 0.01), 5 (p l 0.001),6 (p l 0.05)] but did not decrease in other regions. Significant regional-specific changes were observed between region 4 vs 8 (p l 0.0002). and region 5 vs 8 (p l 0.0001). Similarly, %WTh in the PLW progressively decreased (p l 0.0001) but was unchanged in the IVS. Conclusion These data suggest that sustained rapid LV pacing produces regional myocardial dysfunction in the initial development of LV failure. Myocardial contrast echocardiography suggests that relative hypoperfusion may contribute to regional myocardial dysfunction in this model. Download : Download high-res image (107KB) Download : Download full-size image