胸部外科

Redo coronary artery bypass grafting（ CABG） may be the most technically challenging operations in cardiac surgery. The coronary artery disease is more advanced, and the coronary targets may be suboptimal. Furthermore, the patients are typically older and sicker compared to those undergoing primary CABG. The frequency of redo CABG relative to total CABG procedures has been decreasing over time. Perioperative mortality for redo CABG is reported to be as high as three times that of primary CABG, but this risk is reduced with experience. Redo CABG is a complicated operation, and appropriate surgical strategies are essential for achieving good outcomes.

Recent progressive application of percutaneous coronary intervention has decreased the number of reoperative coronary artery bypass grafting（ CABG）, as well as that of primary CABG. Since CABG in patients with previous heart valve surgery is relatively uncommon, it is unfamiliar to many cardiac surgeons. Therefore, in-depth strategy for redo surgery is mandatory to perform the operation safely. This article summarizes the perioperative management and surgical techniques of reoperative CABG in patients with previous heart valve surgery.

With increasing number of patients undergoing aortic valve replacement, many patients are at risk for redo aortic valve surgery. It has been reported that 56.2％ of the patients receiving a bioprostheis and 7.4％ of the patients receiving a mechanical valve need reoperation 20 years after the primary surgery. Although valve in valve transcatheter aortic valve implantation （TAVI） is a less invasive approach, redo aortic valve replacement is preferred for patients with prosthetic valve endocarditis, small aortic valve prosthesis and poor access for TAVI. Special care should be prepared for safe re-sternotomy, cardiopulmonary bypass management and strategy for cardioplegia. As reported from high volume centers, redo aortic valve replacement could be performed at a similar mortality rate as the primary surgery. New prostheses such as sutureless valve and rapid deployment valve could be useful, as well as minimally invasive cardiac surgery approach, which may prevent tissue injury. However, redo aortic valve replacement via re-sternotomy remains a gold standard. Techniques and strategy for redo aortic valve replacement are reviewed.

It has been reported that there are some risks of coronary artery graft injury while redo sternotomy was required for valve surgery after coronary artery bypass grafting （CABG）. Also it is well known that clinical results after graft injury was poor. For avoiding graft injury, coronary artery graft must be placed away from the sternum at the time of initial CABG. For redo sternotomy, 3-dimensional-computed tomography can be useful. For aortic valve surgery after CABG, treatment of patent in-situ graft have to be discussed. For common practice, dissecting and clamping the patent in-situ graft during cardiac arrest were required. However, there are some reports showing good clinical results with moderate hypothermia, non-dissection and non-clamping graft. Furthermore, less mobidity rate results of transcatheter aortic valve implantation（ TAVI） after CABG was reported. For mitral valve surgery after CABG, right mini-thoracotomy was reported as preferred procedure recently. Dissection area could be reduced than re-median sternotomy, although clamping aorta and patent graft were technically difficult. Two procedures were reported such as hypothermia and ventricular fibrillation or normothermia and beating heart. MitraClip procedure can be considered for high risk patients. Newly developed surgical and catheter technique may change the strategy for heart valve disease after CABG.

The keys to successful repeat mitral valve repair are careful selection of eligible patients and the use of high-quality surgical techniques. Regarding patient selection, patients with soft leaflet tissue, redundant rough-zone areas, and posterior mitral leaflet regions are good candidates for repeat repair. Autologous pericardial patch reinforcement for sutured dehiscence line, triangular resection for residual excess tissue, and sophisticated neo-chord reconstruction are high-quality techniques that increase the durability of repeat repair．

Transcatheter mitral valve intervention, including repair and replacement, has been developed as an alternative treatment to mitral valve surgery with advanced technology in recent years, but the therapeutic indication is still limited to only a part of all, high-risk or inoperable patients. Although reoperative valve surgery is generally known to be associated with increased morbidity and mortality, conventional mitral valve surgery after previous aortic valve replacement is needed due to limited usage of catheter intervention as increasing of aged population. It is usually necessary to undergo redo median sternotomy with care as same as other reoperation, or right thoracotomy approach in some cases. In any cases, there is a tendency to poor visualization of the mitral valve, in especially, a view of anterior annulus due to rigid aortic prosthetic cuff. Of course, optimal visualization of the mitral valve is a successful key factor in reliable maneuver for either repair or replacement. Here we describe operative tips and pitfalls including operative indication, re-opening of the chest, left atrial approach.

We presented our experiences of reoperative aortic root replacement and technical details. Between April 2000 and February 2021, 80 patients underwent reoperative aortic root replacement （60 male, mean age 59.3±14.4 years）. The previous procedures were ascending or arch replacement in 36, aortic valve replacement （AVR） in 32, and aortic root replacement in 12. Surgical indications for reoperation included infective endocarditis or graft infection （n＝31）, root dilation/dissection （n＝26）, pseudoaneurysm（n＝13）, aortic valve regurgitation（ n＝7）, and structural valve dysfunction（ n＝3）. Mean interval from 1st operation was 6.7±6.1 years. Reoperative procedures were composed of modified Bentall（ n＝27）, reimplantation technique （n＝25）, root replacement with stentless valve （n＝16）, partial remodeling/patch plasty（ n＝5）, Commando operation（ n＝5）, and Ross operation（ n＝2）. In-hospital mortality was 8.8％（7/80 patients）. The causes of mortality were sepsis in 3, pneumonia in 2, bowel perforation in 1, and anastmotic rupture with mediastinitis in 1. Freedom from 3rd time aortic root related opera tion was 90.8±4.8％ at 10 years. Actuarial survival after reoperation was 67.3±6.6％ at 10 years. In conclusion, the clinical short-and long-term outcomes of reoperative aortic root replacement were reasonable even in patients with complicated aortic pathologies.

Surgeries for non-dissected aortic arch diseases have been performed with increasing frequency in recent years. Accordingly, the awareness of the pitfalls in reoperation after a previous ascending aortic replacement is needed. Indications for redo total aortic arch replacement after a prior ascending aortic replacement include pseudoaneurysm formation at the distal anastomosis site and newly developed aortic arch aneurysms. At reoperation, we should take the assurance of safety during re-sternotomy into consideration. Cannulation sites should be strategically selected. The radiologic features of the high-risk re-sternotomy include a close approximation（ ＜5 mm） between the sternum and the aorta or the previously placed vascular prosthesis and a presence of pseudoaneurysm underneath the sternum. In such cases, it is reasonable to establish partial cardiopulmonary bypass and selective cerebral perfusion via bilateral carotid artery cannulation prior to sternotomy to avoid disastrous neurological complications. Adhesions around a previously placed vascular prosthesis with innominate vein or main pulmonary artery can be troublesome；thus, care must be taken so as not to injure the surrounding vital organs. Liberal employment of hypothermia can be life-saving by preserving brain, heart and other vital end-organs at the expense of prolonged procedure time.

Redo or repetitive surgeries for residual distal dissection after the limited proximal aortic repair for Stanford type A acute aortic dissection remains challenging. Depending on targeted aortic segments, the strategy including a median or lateral approach and one or two-staged repairs would be determined with careful consideration for patient’s age and conditions of the brain, heart, lung, liver, and kidney. Given the aortic arch involved, for young and low-risk patients, an aggressive one-stage repair of the entire arch to descending aorta through a left thoracotomy is attempted. In particular, with our left antero-axillary approach, it would be much easier with a better surgical field from the ascending aorta to the descending/thoracoabdominal aortic segments. Meanwhile, two-staged repairs are more beneficial for elderly higher-risk patients, which consists of the first total arch replacement （TAR） with elephant trunk （ET） through a median sternotomy followed secondly by an open descending/thoracoabdominal aortic repair through a left thoracotomy or by less-invasive thoracic endovascular aortic repair. In additions, TAR with a frozen ET （FET） has been a new option for downstream aortic remodeling. Consequently, in the initial repair, TAR with FET or ET has been more aggressively performed to prevent such troublesome behaviors of the residual aortic dissection.