Expanding minimally invasive innovation to complex mitral reoperations.

Abstract

The increasing familiarity with minimally invasive mitral surgical approaches have enabled the technical progression from sternotomy to mini-sternotomy, from direct vision mini-thoracotomy to video-assisted mini-thoracotomy, and now to a resurgence of robotic-assisted mitral surgery [1]. Maintaining quality outcomes through this step-wise progression is essential. Perfusion and cannula enhancements facilitating non-sternotomy mitral access can be applied safely using conventional cross-clamping and endoballoon aortic occlusion, even in reoperations [2]. Similarly, good outcomes to isolated mitral reoperations can be accomplished via right thoracotomy on the normothermic centrally cannulated beating heart. At our institution, this has become the favoured method to address these complex cases, with the majority of patients extubated immediately postoperatively without blood products. In this issue of the Multimedia Manual of Cardio-Thoracic Surgery, Botta et al. [3] from Milano bravely outline their approach to complex reoperations using a minimally invasive approach on the unclamped aorta. Their experience with 40 patients between 2008 and 2014 showcases their use of moderate hypothermic ventricular fibrillation including an elegantly performed video case example on a 75-year-old patient requiring a fourth time redo operation. Though the average ejection fraction was 50%, their patients were admittedly at high risk with one-quarter having more than one prior cardiac operation, one-third in renal failure and half having undergone prior surgical revascularization. The authors believe that fibrillatory arrest performed between 27 and 28° centigrade for an average time of 95 min with transient flow reductions enabled better valve exposure with minimal dis section while still achieving adequate myocardial protection. However, in this series of complex patients, 10% (4/40) had low output states requiring intra-aortic balloon pump assistance, 7.5% (3/40) had a cerebrovascular event, the majority were transfused and there was a 10% (4/40) in-hospital operative mortality. Whether centrally or peripherally cannulated, the use of fibrilla tory arrest under moderate hypothermia for redo mitral operations remains popular in selected experienced centres. As demon strated by the authors, this may indeed be a useful tool in certain cases where surgical courage is called upon to navigate otherwise very complex patients through a mitral reoperation. While fibrillatory arrest can be useful, history recounts that even with hypothermia, the ventricular subendocardium may be suboptimally protected when the perfusion pressure is reduced to the levels used in clinical cardiac surgery [4]. The reduced wall stress and myocardial demands from an empty beating heart or arrested heart may continue to have a role in these complex operations. Moreover, the use of CT angiographic mapping preoperatively, as done by the authors, is essential to avoid complications of femoral cannulation in mitral reoperations [1, 5]. Botta et al. have provided us with a progressive approach to add to the armamentarium of high-risk mitral reoperations. However, as programmes attempt these cases for the first time, the use of outcome-focused patient-specific alternate cannulation and perfusion strategies should still be considered. Attention to safety and quality should always be kept at the forefront as we expand the application of technical innovation to a broader array of patients.