National Heart, Lung, and Blood Institute, National Institutes of Health: the Cardiothoracic Surgery Research Program, Bethesda, MD 20892, USA.
J Thorac Cardiovasc Surg. 2010 Feb;139(2):424-30. doi: 10.1016/j.jtcvs.2009.08.005. Epub 2009 Dec 6.
Percutaneous valve replacements are presently being evaluated in clinical trials. As delivery of the valve is catheter based, the safety and efficacy of these procedures may be influenced by the imaging used. To assist the surgeon and improve the success of the operation, we have performed transapical aortic valve replacements using real-time magnetic resonance imaging guidance.
Twenty-eight swine underwent aortic valve replacement by real-time magnetic resonance imaging on the beating heart. Stentless bioprostheses mounted on balloon-expandable stents were used. Magnetic resonance imaging (1.5 T) was used to identify the critical anatomic landmarks. In addition to anatomic confirmation of adequate placement of the prosthesis, functional assessment of the valve and left ventricle and perfusion were also obtained with magnetic resonance imaging. A series of short-term feasibility experiments were conducted (n = 18) in which the animals were humanely killed after valve placement and assessment by magnetic resonance imaging. Ten additional animals were allowed to survive and had follow-up magnetic resonance imaging scans and confirmatory echocardiography at 1, 3, and 6 months postoperatively.
Real-time magnetic resonance imaging provided superior visualization of the landmarks needed. The time to implantation after apical access was 74 +/- 18 seconds. Perfusion scanning demonstrated adequate coronary flow and functional imaging documented preservation of ventricular contractility in all animals after successful deployment. Phase contrast imaging revealed minimal intravalvular or paravalvular leaks. Longer term results demonstrated stability of the implants with preservation of myocardial perfusion and function over time.
Real-time magnetic resonance imaging provides excellent visualization for intraoperative guidance of aortic valve replacement on the beating heart. Additionally, it allows assessment of tissue perfusion and organ function that is not obtainable by conventional imaging alone.
经皮瓣膜置换术目前正在临床试验中进行评估。由于瓣膜的输送是基于导管的，因此这些程序的安全性和有效性可能受到所使用的成像技术的影响。为了协助外科医生并提高手术的成功率，我们已经使用实时磁共振成像引导进行了经心尖主动脉瓣置换术。
28 头猪在跳动的心脏上进行实时磁共振成像引导的主动脉瓣置换术。使用无支架生物瓣，安装在球囊扩张支架上。磁共振成像（1.5 T）用于识别关键解剖学标志。除了对假体放置位置进行解剖学确认外，还通过磁共振成像获得了对瓣膜和左心室的功能评估以及灌注情况。进行了一系列短期可行性实验（n=18），在这些实验中，动物在放置瓣膜并通过磁共振成像评估后被人道处死。另外 10 只动物允许存活，并在术后 1、3 和 6 个月进行了后续磁共振成像扫描和确认性超声心动图检查。
实时磁共振成像提供了更好的解剖标志可视化效果。心尖入路后的植入时间为 74±18 秒。灌注扫描显示所有动物的冠状动脉血流充足，功能成像记录显示心室收缩力在成功植入后得到保留。相位对比成像显示瓣膜内或瓣周漏最小。长期结果显示，随着时间的推移，植入物保持稳定，心肌灌注和功能得到保留。
实时磁共振成像为在跳动的心脏上进行主动脉瓣置换术的术中引导提供了出色的可视化效果。此外，它还可以评估组织灌注和器官功能，而这些是常规成像无法单独获得的。
