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-PT SD ) 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-PT SD 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-PT SD between subendo and subepi in A group in all conditions ( all P < 0 .05) . In group B ,the RD-PT and RD-PT SD 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-PT SD of subendo were significant different on 2 W compared with those on baseline condition ( all P <0 .05) ;the RD-PT and RD-PT SD of subendo ,subepi were significant different on 3 W compared with baseline condition ( all P < 0 .05) ;the RD-PT and RD-PT SD 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-PT SD of LV subendo and subepi . Power 3 W can result in dyssynchrony of LV myocardial mechanics .