Masroor Saqib, Jahnke Mary-Ellen, Carlisle Antoine, Cartier Catherine, Lalonde Jean-Pierre, Macneil Timothy, Tremblay Andre, Clubb Fred
Department of Cardiothoracic Surgery, Hackensack University Medical Center, Hackensack, NJ 07601, USA.
J Thorac Cardiovasc Surg. 2008 Jun;135(6):1327-33. doi: 10.1016/j.jtcvs.2007.12.038.
The objective of this study was to investigate whether epicardial cryoablation could achieve sufficient endocardial hypothermia to create transmural lesions leading to acute and sustained pulmonary vein isolation in a normothermic beating-heart model.
Thirty-five- to 45-kg pigs underwent median sternotomy. Epicardial cryoablation was performed on the right ventricle after insertion of thermocouples. Endocardial temperatures from thermocouples were recorded continuously and correlated with the thickness of the myocardium. Thirteen animals underwent pulmonary vein isolation as a box lesion by using 5-minute epicardial cryoablation. Endocardial temperatures were measured in 5 of these animals. Ten animals survived for 7 or 30 days. Electrical isolation was tested at the time of surgical intervention and again at death. Hearts were removed en bloc and submitted for gross and microscopic examination.
Endocardial temperature varied inversely with tissue thickness, ranging from -60 degrees C in 5-mm-thick tissue to staying unchanged in tissue more than 10 mm thick. During pulmonary vein isolation, median endocardial temperatures were between -1 degrees C and -22 degrees C. Acute electrical isolation was achieved in all 13 animals. All except one of the animals maintained electrical isolation long-term. Histologic analysis revealed transmurality in 89% of sections, although none of the box lesions were completely transmural.
Epicardial cryoablation can produce long-term pulmonary vein isolation in a beating heart. Dose-response studies demonstrate consistent endocardial hypothermia in tissues up to 7 mm thick. To our knowledge, this is the first report documenting endocardial hypothermia during epicardial cryoablation. This technology holds promise for performing the complete maze procedure on a beating heart.
本研究旨在探讨在常温跳动心脏模型中，心外膜冷冻消融是否能实现足够的心内膜低温，以形成透壁性损伤，从而导致急性和持续性肺静脉隔离。
对体重35至45千克的猪进行正中胸骨切开术。插入热电偶后，在右心室进行心外膜冷冻消融。连续记录热电偶测得的心内膜温度，并与心肌厚度相关联。13只动物通过5分钟的心外膜冷冻消融进行肺静脉隔离，作为盒状损伤。其中5只动物测量了心内膜温度。10只动物存活7天或30天。在手术干预时和死亡时分别测试电隔离情况。将心脏整块取出，进行大体和显微镜检查。
心内膜温度与组织厚度呈反比，在5毫米厚的组织中温度可达-60℃，在超过10毫米厚的组织中温度保持不变。在肺静脉隔离期间，心内膜温度中位数在-1℃至-22℃之间。所有13只动物均实现了急性电隔离。除1只动物外，其他所有动物均长期维持电隔离。组织学分析显示，89%的切片存在透壁性，尽管没有一个盒状损伤完全透壁。
心外膜冷冻消融可在跳动的心脏中实现长期肺静脉隔离。剂量反应研究表明，在厚度达7毫米的组织中，心内膜低温具有一致性。据我们所知，这是第一份记录心外膜冷冻消融期间心内膜低温的报告。这项技术有望在跳动的心脏上完成完整的迷宫手术。
