Effects of different ultrasound power application on left ventricular myocardium synchrony in vivo open-chest Beagle canines

Abstract

Objective To evaluate left ventricular (LV) myocardial mechanical synchrony with contrast agent and different power irradiation in open-chest Beagle canines. Methods The anesthetized open-chest Beagle canines were assigned into two groups randomly: Group A (n=6) for baseline, diagnostic ultrasound power irradiation (300 mW) 5 min, combined with contrast agent irradiation 5 min and contrast agent 20 min conditions; Group B (n=6) for baseline and intensity ultrasound irradiation (1 W, 2 W and 3 W, 5 min respectively) conditions. The standard short-axis gray-scale views at levels of mitral annulus (MV), papillary muscle(PM), and apex(AP) during 3 complete cardiac cycles in open-chest Beagle canine models were acquired. The global radial displacement peak time (RD-PT) and standard deviation of peak time (RD-PTSD) of LV subendomyocardium (subendo) and subepimyocardium (subepi) were measured and analyzed by using a dedicated Syngo velocity vector imaging (VVI) method. Results In group A, compared with baseline condition, the RD-PT and RD-PTSD of subendo and subepi had no significant different among diagnostic power irradiation, contrast agent irradiation 5 min and contrast agent 20 min (all P<0.05). There was no significant different in the RD-PT and RD-PTSD between subendo and subepi in A group in all conditions (all P<0.05). In group B, the RD-PT and RD-PTSD of subendo and subepi with power 1 W, 2 W and 3 W was higher than those with baseline condition; the RD-PT and RD-PTSD of subendo were significant different on 2 W compared with those on baseline condition (all P<0.05); the RD-PT and RD-PTSD of subendo, subepi were significant different on 3 W compared with baseline condition (all P<0.05); the RD-PT and RD-PTSD were significant difference between subendo and subepi in only 3 W condition (all P<0.05). Conclusions Diagnostic ultrasound power irradiation 5 min and combined with contrast agent irradiation 5 min and contrast agent 20 min conditions do not effect the synchrony of LV myocardial mechanics. Power more than 1 W can induce the delay of RD-PT and RD-PTSD of LV subendo and subepi. Power 3 W can result in dyssynchrony of LV myocardial mechanics. Key words: Sonication; Ventricular function, left; Beagle canines; Synchrony