DETECTION OF REGIONAL LEFT-VENTRICULAR DYSFUNCTION IN EARLY PACING-INDUCED HEART-FAILURE USING ULTRASONIC INTEGRATED BACKSCATTER

Background It has been demonstrated that cyclic variation of ultrasoni c integrated backscatter (CVIBS) may be useful in detecting altered ph ysical conditions in the heart. However, no previous study has examine d serial changes of CVIBS in the myocardium during the development of left ventricular dysfunction. Methods and Results We examined alterati ons of CVIBS in pacing-induced cardiac dysfunction. Eight pigs (36 +/- 2 kg) were studied before and sequentially during sustained rapid ven tricular pacing (225 +/- 9 beats per minute). CVIBS was measured in th e IVS and left ventricular PLW before pacing and daily for 4 days afte r onset of pacing. Five additional pigs (35 +/- 10 kg) were examined a fter 14 days of pacing. Regional function and CVIBS were assessed with pacemakers inactivated. A quantitative integrated backscatter imaging system (two-dimensional format) was used. Over 4 days of pacing, the magnitude of CVIBS progressively decreased in the PLW but was unchange d in the IVS, findings that persisted at 14 days. Percent wall thicken ing in the PLW progressively decreased to a greater degree than percen t wall thickening in the IVS. A linear relation between the magnitude of CVIBS and percent wall thickening was found. At 14 days, blood flow to the two regions was similar but regional differences in CVIBS pers isted. Conclusions Rapid left ventricular pacing produces abnormalitie s of regional myocardial function within 48 hours of pacing. Regional myocardial dysfunction is accompanied by a reduction in CVIBS in the s ame region.