University of Nebraska Medical Center, Omaha, Nebraska, United States of America.
PLoS One. 2013 Jul 29;8(7):e69780. doi: 10.1371/journal.pone.0069780. Print 2013.
Ultrasound induced cavitation has been explored as a method of dissolving intravascular and microvascular thrombi in acute myocardial infarction. The purpose of this study was to determine the type of cavitation required for success, and whether longer pulse duration therapeutic impulses (sustaining the duration of cavitation) could restore both microvascular and epicardial flow with this technique. Accordingly, in 36 hyperlipidemic atherosclerotic pigs, thrombotic occlusions were induced in the mid-left anterior descending artery. Pigs were then randomized to either a) ½ dose tissue plasminogen activator (0.5 mg/kg) alone; or same dose plasminogen activator and an intravenous microbubble infusion with either b) guided high mechanical index short pulse (2.0 MI; 5 usec) therapeutic ultrasound impulses; or c) guided 1.0 mechanical index long pulse (20 usec) impulses. Passive cavitation detectors indicated the high mechanical index impulses (both long and short pulse duration) induced inertial cavitation within the microvasculature. Epicardial recanalization rates following randomized treatments were highest in pigs treated with the long pulse duration therapeutic impulses (83% versus 59% for short pulse, and 49% for tissue plasminogen activator alone; p<0.05). Even without epicardial recanalization, however, early microvascular recovery occurred with both short and long pulse therapeutic impulses (p<0.005 compared to tissue plasminogen activator alone), and wall thickening improved within the risk area only in pigs treated with ultrasound and microbubbles. We conclude that although short pulse duration guided therapeutic impulses from a diagnostic transducer transiently improve microvascular flow, long pulse duration therapeutic impulses produce sustained epicardial and microvascular re-flow in acute myocardial infarction.
超声空化已被探索用于溶解急性心肌梗死中的血管内和微血管血栓。本研究旨在确定成功所需的空化类型，以及更长的脉冲持续时间治疗脉冲（维持空化持续时间）是否可以恢复这种技术的微血管和心外膜血流。因此，在 36 只高脂血症粥样硬化猪中，在左前降支中段诱导血栓闭塞。然后将猪随机分为以下三组：a）单独使用半剂量组织型纤溶酶原激活剂（0.5mg/kg）；或相同剂量的纤溶酶原激活剂和静脉内微泡输注，分别使用 b）引导高机械指数短脉冲（2.0 MI；5 usec）治疗超声脉冲；或 c）引导 1.0 机械指数长脉冲（20 usec）脉冲。被动空化探测器表明，高机械指数脉冲（无论是短脉冲还是长脉冲持续时间）都会在微血管内引起惯性空化。随机治疗后的心外膜再通率在接受长脉冲持续时间治疗脉冲的猪中最高（83%对比短脉冲为 59%，单独使用组织型纤溶酶原激活剂为 49%；p<0.05）。然而，即使没有心外膜再通，短脉冲和长脉冲治疗脉冲也会早期恢复微血管血流（与单独使用组织型纤溶酶原激活剂相比，p<0.005），并且只有在超声和微泡治疗的猪中，风险区域内的壁增厚才会改善。我们的结论是，尽管诊断换能器的短脉冲持续时间治疗脉冲会短暂改善微血管血流，但长脉冲持续时间的治疗脉冲会在急性心肌梗死中产生持续的心外膜和微血管再灌注。
