超声辐照诱导左心室跨壁心肌力学状态变化的实验研究

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

目的 观察不同强度超声辐照结合超声造影干预对比格犬左心室心肌力学状态的影响,量化评价超声辐照诱导的左心室跨壁心肌力学变化特征.方法 12只健康比格犬开胸模型,随机分为A、B两组各6只.A组：诊断型超声探头输出声能3～300 MW,采集超声辐照5 min、注射造影剂后辐照5 min和注射造影剂后20 min左心室短轴二尖瓣水平、乳头肌水平、心尖水平3个完整心动周期实时灰阶图像;B组：治疗型超声探头输出声能分别为1W、2W、3W,分别采集经超声辐照5 min后左心室短轴二尖瓣水平、乳头肌水平、心尖水平3个完整心动周期实时灰阶图像.应用Syngo图像工作站,分别获取3个短轴切面共18个节段前间隔、前壁、侧壁、后壁、下壁、后间隔的心内膜下心肌和心外膜下心肌周向应变的时间变化曲线并测量其峰值和达峰时间.评价不同干预状态比格犬左心室心肌峰值周向应变及其达峰时间相关力学参数变化.结果 ①A组超声辐照5 min、注射造影剂后辐照5 min、20 min心内膜下心肌和心外膜下心肌峰值周向应变与基础状态比较均有增大的趋势,大多数节段比较差异有统计学意义（P＜0.05）;B组超声输出声能1W与基础状态比较心内膜下心肌呈增大趋势,其中4个节段差异有统计学意义（P＜0.05）;超声输出声能2W、3W与基础状态比较心内膜下心肌呈逐渐下降趋势,部分节段比较差异有统计学意义（P＜0.05）.②A组、B组相同状态相同节段心内膜下心肌和心外膜下心肌峰值周向应变的达峰时间少部分节段差异有统计学意义（P＜0.05）;B组不同状态同一节段心内膜下和心外膜下心肌峰值周向应变的达峰时间有统计学差异的节段比较A组增多.结论 单纯诊断剂量超声辐照、诊断剂量超声辐照结合超声造影微泡干预以及治疗剂量超声辐照输出声能1W时可诱导左心室心肌周向应变增大,适当剂量超声辐照对左心室心肌具有正性肌力作用;超声辐照输出声能2W、3W时诱导在体比格犬左心室心肌周向应变下降和达峰时间延迟,推测较大剂量超声辐照对左心室心肌机械功能可能存在损伤.

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.