Echocardiographic study of ultrasound irradiation induced left ventricular myocardial transmural mechanical changes

Abstract

Objective To evaluate the changes of segmental and the transmural myocardial peak circumferential strain (CS) of left ventricular(LV) wall with ultrasound irradiation and conbined with ultrasound contrast agent.To provide a reliable database to optimize mechanical effect of LV myocardium.To determine whether diagnostic and therapeutic dosage of ultrasound irradiation or combined with ultrasound contrast agent could induce a positive inotropic action on LV myocardium.Methods The standard short-axis gray scale views at levels of mitral annulus (MV),papillary muscle (PW) and apex (AP)during three complete cardiac cycles in open-chest Beagle canine models were acquired.The beagles were assigned into two groups randomly,group A (n =6) for baseline,baseline low dose ultrasound irradiate(3～300 mW) 5 min,combined with contrast agent 5 min and 20 min conditions,group B (n =6) for high dose ultrasound irradiation(1 W,2 W and 3 W)conditions.The CS and time to peak of CS at 18 segments and its subendomyocardium (subendo) and subepimyocardium (subepi) of LV myocardium were measured and analyzed using a dedicated Syngo VVI workstation.Results ①The CS was increased significantly (P ＜ 0.05) on different conditions of ultrasound irradiation in group A compared with CS on baseline condition at the most myocardial segments of LV under different conditions.The CS at four myocardial segments of LV was increased significantly (P ＜0.05) with 1 W ultrasound irradiation dose in group B compared with CS on baseline condition.In group B,2 W and 3 W ultrasound irradiation doses induced a siginificant decreased CS (P ＜0.05) compared with CS on baseline condition at the most myocardial segments of LV.② The difference of time to peak of CS at subendo and subepi of a few segments under different irradiation conditions was demonstrated (P ＜0.05) in the same group.Difference of time to peak of CS of subendo and subepi at the same myocardial segments in group B was bigger than those in group A.Conclusions The CS of LV was increased significantly under low dose ultrasound irradiation and combined with ultrasound contrast agent and decreased under high dose ultrasound irradiation.These findings might indicate a potential positive and negetive inotropic effects on LV myocardial deformation could be induced using ultrasound irradiation. Key words: Ultrasonography; Microbubbles ; Ventricular function,left ; Circumferential strain