Quantitative Analysis Of Ultrasonic Tissue Characterization With Integrated Backscatter On Myocardial Ischemia And Reperfusion:Experimental Study And Clinical Implication

Objective To investigate the changes of the time average integrated backscatter(IB), cyclic variation(CVIB), normalized IB(IB%), normalized CVIB(CVIB%) after acute myocardial ischemia and reperfusion, and the relationship between the changes of CVIB and regional myocardial contractility. To assess the utility of this technique on detection of viable myocardium in patient after acute myocardial infarction and reperfusion. Methods Twelve adult mongrel dogs of either gender were randomly divided into two groups. Both of them were anesthetized with intravenous pentobarbital (30mg/kg). A left thoracotomy was performed and a pericardial cradle employed to exposed the left anterior coronary artery. Transient ischemic injury was produced in six open chest dogs for 1 5mm followed by reperfusion for 1 h. CVIB, CVIB%, IB, IB% and wall thickening were measured before ischemia, at 1 5mm after the onset of ischemia and at 0mm, 30mm, 60mm after reperfiision. The other six dogs? cornary artery was obstructed for 90mm and followed by reperfusion for 1 h. The parameter of LBS were measured before ischemia, at 60mm and 90mm after the onset of ischemia and at 0mm, 60mm after the onset of reperfusion. Short-axis LBS images in 7 patients with AJVII was recorded before and 3, 10, and 21 days after reperfusion and CVIB, CVIB% was obtained in the normal and infarct zones. When CVIB% showed synchrony and asynchrony, we expressed its magnitude as positive and negative values, respectively, called the phase-corrected magnitude. Average wall motion score of the infarct segments was also measured Results 1. Normal myocardium exhibits cardiac cycle-dependent variation of LBS. lB was largest at the end point of systole, was lowest at the end point of diastole. Time averaged lBS of anterior wall, interior wall, anteroseptum wall and posterior wall were 18.01 ?3.87dB, 18.20 ? 3.96dB, 17.58?.41dB, 22.04?.53dB. lB of the posterior wall is higher than others (P<0.05) III ~fIj~i4 2. The cyclic variation of lBS in the ischemia zone is markedly blunted and even shows asynchronous waveform before reperfusion compared with baseline after 1 5mm occlusion of artery. lB and IB% increased after ischemia, began to recover after reperfusion, and recovered to normal after 60mm reperfusion. CVIB , CVIB% and wall thickening magnitudes decreased after ischemia. CVIB, CVIB% recovered to baseline levels within lh after reperfiision, but wall thickening remained depressed for lh after reperfusion. 3.IB, IB% obvious increased in server ischemic group after myocardial ischemia, while CVIB, CVIB% and wall thickening decreased dramatically. No remarkable recovery of CVIB, CVIB% and wall thickening was found after lh reperfusion. 4.The phase-corrected magnitude in patient was lower in the infarct zone than in the normal zone before reperfusion At day 3, the phase-corrected magnitude increased despite no improvement in wall motion. Improvement in wall motion was observed only at day 21. Conclusions Cyclic variation recovers before wall thickening with reperfusion. Its analysis appears to provide a useful index of the presence of viable and potentially salvageable tissue in regions of stunned myocardium that is independent of wall thickening. In patients with AIVII, cyclic variation of lBS is blunted during ischemia but recovers much faster after reperfusion than the improvement...