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Interact CardioVasc Thorac Surg 2009;9:94-97. doi:10.1510/icvts.2008.201038 © 2009 European Association of Cardio-Thoracic Surgery
Mini re-sternotomy for aortic valve replacement in patients with patent coronary bypass graftsDepartment of Cardiovascular Surgery, Villa Maria Cecilia Hospital, Cotignola, Lugo (RA), Italy Received 18 December 2008; received in revised form 26 March 2009; accepted 30 March 2009
*Corresponding author. Via Corriera n.1, Cotignola Lugo (RA), Italy. Tel.: +393356223366; fax: +390545217102.
As the population ages, an increasing number of patients with patent coronary grafts will require subsequent aortic valve replacement. Major operative problems include those associated with re-entry and, in particular, damage of the patent grafts. Between January 2007 and October 2008, 10 patients who had previous coronary bypass surgery underwent aortic valve replacement through upper j-shaped mini re-sternotomy. In all patients the previous grafts were patent. The operation was performed with normothermic cardiopulmonary bypass without dissection and temporary closure of the arterial and venous coronary bypass grafts. The mean age was 73.2±13.6 years. The patients had a mean of 2.8±0.6 bypass grafts. There were no intraoperative complications due to redo ministernotomy and at no time conversion to full re-sternotomy was necessary. No damage to the previous grafts was reported and the incidence of perioperative myocardial infarction was 0%. One patient required a pacemaker implantation for atrio-ventricular block. The in-hospital mortality was 0%. Aortic valve replacement in previous coronary bypass grafting can be performed safely with a mini re-sternotomy. This approach avoids extensive dissection, decreasing the risk of injuries to heart chambers and previous patent coronary grafts with low morbidity and mortality.
Key Words: Aortic valve disease; Ministernotomy; Coronary bypass grafts; Reoperation; Minimally invasive
Reoperation in cardiac surgery is nowadays even more frequent due to aging population. One of the most challenging situations is the treatment of a patient with aortic valve disease after coronary surgery, in particular when coronary grafts are still patent. Injuries to previous patent coronary graft during sternal re-entry or dissection of the heart is the major complication during this operation and is not infrequently fatal [1, 2]. In literature it has been reported a benefit from a minimally invasive approach during aortic valve replacement in terms of decreased bleeding, transfusion need, respiratory function, length of hospital stay and cosmesis [3, 4]. In our department, since 2001, aortic valve replacement through upper j-shaped mini-sternotomy is considered the standard approach for aortic valve replacement. Recently, some authors extended the advantage of mini-sternotomy for aortic valve re-replacement or during aortic valve replacement after previous cardiac surgery [4, 5]. We report our experience with aortic valve replacement using the upper j-shaped re-sternotomy in patients with previous patent coronary bypass grafting.
Preoperative computed tomography (CT) was performed in all patients to evaluate the grafts and mediastinal structure's location. External defibrillator paddles were placed in all patients. The surgical technique is shown in Fig. 1. An upper j-shaped mini-sternotomy was carried out with an oscillating saw to the 3rd or 4th intercostal space. The femoral vessels were draped but not exposed. Mediastinal dissection was limited to the ascending aorta and the right atrium. The arterial cannula was placed in the ascending aorta and the venous cannula in the right appendage. Left ventricular venting was managed through the right superior pulmonary vein after aortic cross-clamping. During cardiopulmonary bypass, esophageal temperature was maintained at 34 °C in all patients. No attempts were made to dissect and clamp the LITA in all patients, only a limited dissection of proximal vein-graft anastomosis was performed just to avoid damage during aortic cross-clamping. After a transverse aortotomy, the aortic valve was excised and replaced using the continuous suture technique. All patients had one dose of antegrade blood cardioplegia (34 °C), and when the heart resumed a sinus rhythm or ventricular fibrillation, usually after a few minutes, it was elected to use no additional cardioplegia, and the heart was allowed to beat empty throughout the procedure.
After closure of the aorta and removal of the aortic cross-clamp, de-airing was accomplished using aortic vent suction and trans-esophageal echocardiography guidance. The heart was then weaned from the extracorporeal circulation, the patient decannulated and the chest closed in the normal manner with three metal bands. Three patients required defibrillation after aortic clamp removing, performed by external defibrillator paddles in two cases and by pediatric internal defibrillator paddles in one case without additional mediastinal dissection. Routinely, two chest tubes were placed in the mediastinal cavity. Atrial and ventricular pacing wires were always positioned.
From January 2007 to October 2008, 22 patients underwent aortic valve replacement after previous coronary by-pass grafts. Of these, ten patients with multiple and patent coronary grafts underwent aortic valve replacement through an upper j-shaped mini re-sternotomy. The mean time from the first operation was 113±57.4 S.D. months (range 2–216 months). The mean number of grafts was 2.8±0.6 S.D. (range 2–4). Distribution of previous grafts is shown in Table 1. The preoperative characteristics of patients are summarized in Table 2.
Four patients underwent aortic valve replacement using a bovine pericardial prosthesis (Mitroflow, Sorin Group Canada Inc, Mitroflow Division), four patients had a porcine valve (Mosaic, Medtronic Inc, Minneapolis, Santa Ana, CA, USA), one patients had a stentless valve procedure (Freedom Solo, Sorin Group Canada Inc, Mitroflow Division), and one patient had the implantation of a mechanical valve (Carbomedics, Sorin Biomedica Cardio S.r.l Saluggia, VC, Italy) because of younger age. The mean ischemia time and cardiopulmonary bypass time were 52.2±20.2 (range 38–100 min) and 70±22.5 (range 48–125 min), respectively.
Intra-operative and postoperative characteristics are summarized in Table 3. No conversion to full re-sternotomy was necessary, and no injury to heart structures or previous coronary grafts occurred. No patients required re-thoracotomy for bleeding. Cardiopulmonary bypass was always performed by central cannulation without the need of peripheral cannulation. We had no sternal instability or infection of the surgical wound. We had no renal, respiratory and neurological complications. We had no post- operative myocardial infarction, defined as a new Q-wave in the electrocardiogram, creatine kinase-MB (CPK-MB)
The mean follow-up time was 6.6±3 months (4–14 months). All patients are in good clinical condition and free of valve related complications.
With the aging of the population, an increasing number of patients who have undergone previous cardiac surgery are presenting to their surgeon in need of a second operation. In particular, aortic valve replacement is challenging in the setting of patent coronary bypass grafts. The major technical problems are the risk of graft injuries during sternal re-entry or mediastinal dissection, and the choice of myocardial protection strategies during the operation [1, 2]. In spite of the continuous evolving technologies in cardiac surgery, the reported mortality for aortic valve replacement in previous coronary bypass grafting is 6.2–18%. Injuries of patent LIMA-to-LAD occur with a frequency of 3–13% [1, 2] with perioperative myocardial infarction higher than 6% and stroke higher than 8% in different series [6–8]. Different surgical techniques have been used in clinical practice with the aim to reduce morbidity and mortality [4, 8, 9]. Moreover, catheter-based aortic valve replacement approach is a promising technique for these patients in the future, but until now the surgical approach should still be considered the gold standard treatment even in high-risk patients [10]. In our series we selected only patients in whom all the grafts were patent. We used a minimally invasive approach to perform aortic valve replacement, leaving the arterial graft in perfusion and without dissection and occlusion of the vein grafts. Necessity of additional surgical revascularization, previous mediastinitis, dilatative cardiomyopathy, previous high-dose radiotherapy, severe calcification of the ascending aorta and graft location close to the sternum detected by preoperative CT-scan, are considered contraindication to perform this technique. Minimally invasive aortic valve replacement through partial upper j-shaped mini-sternotomy has become an alternative technique for aortic valve replacement [3–5]. The limited incision makes opening and closure of the sternotomy easier and faster with a very low risk of sternal instability and infection [4]. Upper ministernotomy guarantees an optimal surgical exposure and access to the aortic root. Moreover, in literature the smaller incision was associated with less postoperative pain and a better respiratory function [3]. In the case of reoperation the ministernotomy will reduce the area of pericardiolysis and reduce operative time [4, 5]. Mediastinal dissection is limited to the ascending aorta and a small piece of right atrium just for the purpose of cannulation. The right ventricle does not need to be dissected with lower risk of injuries. Concerning optimal myocardial protection in this setting, we found no definitive evidence in literature [6, 8, 9]. In a recent study, Smith et al. [8] failed to demonstrate any increased risk in perioperative mortality from leaving the LIMA graft unclamped. They had no statistical difference in the incidence of perioperative myocardial infarction between clamped and unclamped LIMA graft groups, irrespective of myocardial protection strategies. In their experience, the process of dissecting the LIMA graft resulted in seven graft injuries. Probably the best way to reduce morbidity and mortality is to avoid dissection and occlusion attempts of the LIMA-to-LAD, reducing the risk of LIMA injuries. Also, injuries and distal embolism due to a manipulation of patent but atherosclerotic vein grafts could be reduced, avoiding dissection and heart manipulation. In our opinion the use of deep hypothermia and/or complex techniques for graft's selective perfusion are not justified. All of these attempts are time consuming and make the operation more cumbersome and increasing the operation time. In our opinion a shorter operation and clamping time represent the best way to avoid problems in these patients. We leave the arterial grafts patent (LIMA or RIMA) and we give a traditional shot of antegrade blood cardioplegia in the aortic root and retrograde blood cardioplegia if aortic regurgitation is more than mild. The no-touch technique on the vein grafts is used. If the heart continues to beat or re-starts to beat we leave it beating. In our experience, we had no ischemic complications or postoperative myocardial infarctions, as well as no problems during weaning from cardiopulmonary bypass. In conclusion, in our experience, the upper re-sternotomy with no-touch grafts technique in previous patent coronary bypass grafting is a safe approach with low morbidity and mortality. Because of the small dimension of the population and the lack of a control group, further studies are required in the future to understand which strategy guarantees the best results in these complex patients.
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Abstract
1. Introduction
50 IU/l, and CK-MB/CK ratio >10% or new wall motion abnormality on echocardiography. One patient required a pacemaker implantation because of postoperative atrio-ventricular block. Two patients had postoperative atrial fibrillation. 
