诊断超声VFLASH技术增强大鼠急性心肌缺血左心射血功能的实验研究

目的 研究诊断超声(diagnostic ultrasound,DUS) VFLASH技术对大鼠急性心肌缺血模型左室射血功能的治疗改善作用.方法 6 ～ 8周龄健康雄性SD大鼠70只,用随机数字表法分为5组:高机械指数组(HMI,MI = 1. 4,n = 11) 、低机械指数组(LMI,MI = 0. 7,n = 17) 、HMI联合微泡(MB) 组(HMB,n = 15) 、LMI联合微泡组(LMB,n = 16) 和对照组(n = 11) .结扎冠状动脉前降支建立大鼠急性心肌缺血模型后,分别于24、72、96 h按照分组实施超声治疗, 28 d行心脏射血分数(EF) 超声检测.超声治疗参数为: 频率4 MHz,脉冲重复频率20 Hz,脉冲宽度在MI =1. 4时为5个周期、MI =0. 7时为18个周期,脉冲持续时间1. 2 s,脉冲间隔时间2 s,持续时间1 200 s.记录各组鼠的生存状态,以28 d为终止目标,比较各组大鼠存活率.术后第28天比较各组鼠左室射血功能(EF值),并取各组鼠心脏组织HE染色观察心肌组织变化.结果 ①存活率: HMI组72％,LMI组47％,HMB组20％,LMB组50％,对照组82％,仅HMI组高于HMB组,差异具有统计学意义(P＜0. 05),其余各组之间差异无统计学意义(P＞ 0. 05) .②EF: HMI组(87. 71 ± 4. 69) ％,LMI组(78. 04 ± 7. 35) ％,HMB组(75. 09 ± 9. 47) ％, LMB组(76. 43 ± 6. 83) ％,对照组(64. 97 ± 9. 37) ％,单纯超声组(即HMI和LMI组) 和LMB组的EF值均明显高于对照组,HMI组高于LMI组,差异均具有统计学意义(P＜0. 05),LMI与LMB之间差异无统计学意义(P＞ 0. 05) .③对照组心肌组织大片坏死、纤维化,各治疗组纤维化面积无明显差异.结论超声辐照VFLASH技术能够有效改善急性心肌缺血大鼠的心功能,并且单纯高机械指数超声效果较好,更安全.

Diagnostic ultrasound VFLASH improves left ventricular ejection function in rats with acute myocardial ischemia

Objective To investigate the improvement of cardiac function in acute myocardial ischemia rats by diagnostic ultrasound (DUS) combined with VFLASH (a software which can manipulate microbubble cavitation). Methods A total of 70 healthy male SD rats (6 ～ 8 weeks old) were randomized into 5 groups: high mechanical index group (HMI, MI = 1. 4, n = 11), low mechanical index group (LMI, MI = 0.7, n = 17), HMI combined with microbubble (MB) group (HMB, n = 15), LMI combined with MB group (LMB, n = 16), and control group (n = 11). Acute myocardial ischemia model was established by ligation of anterior descending coronary artery. Ultrasound treatment was performed in corresponding groups in 24, 72 and 96 h after model establishment. The treatment parameters are as follows: frequency 4 MHz, pulse repeated frequency (PRF) 20 Hz, pulse length (PL) 5 cycles for MI = 1. 4 groups and 18 cycles for MI = 0.7 groups, pulse time 1. 2 s, pulse interval time 2 s, duration 1 200 s. The survival status of rats was recorded, and the survival rate was compared among the 5 groups at the end of experiment (28 d). At the 28th day, the rats underwent ultrasonography for cardiac ejection fraction (EF), and the rat heart tissue was collected for pathological changes by HE staining. Results ① The survival rate was 72％ in the HMI group, 20％ in the LMB group, 50％ in the LMB group, and 82％ in the control. The rate of the HMI group was significantly higher than the HMB group (P＜0.05), but no difference was seen in other groups (P＞ 0.05). ② The average EF value was (87. 71 ± 4. 69) ％ in the HMI group, (78. 04 ± 7. 35) ％ in the LMI group, (75. 09 ± 9. 47) ％ in the HMB group, (76. 43 ± 6. 83) ％ in the LMB group, and (64. 97 ± 9. 37) ％ in the control group. The values were significantly higher in the simple ultrasound groups (HMI and LMI groups) and LMB group than the control, and that of HMI higher than that of the LMI groups, with obvious differences (P＜0.05). But there were no differences in the values between the LMI and LMB groups (P＞ 0.05). ③ HE staining displayed that the myocardial tissues were necrotic and fibrotic in the control group, but there was no significant difference in fibrotic area in the treatment groups. Conclusion Ultrasound irradiation in combination with VFLASH can effectively improve the heart function of acute myocardial ischemia rats, with better pure HMI and good safety.