The Brigham and Women's Hospital has pioneered minimal access reoperative aortic valve replacement in patients who previously have undergone coronary artery bypass grafting or other cardiac surgery. We popularized and published our data and have since had more experience with the technique.
According to the STS database, patients requiring a reoperative aortic valve replacement after previous coronary artery bypass grafting have a mortality risk of about 8 to 12% from the procedure. The risks are associated with the performance of a reoperation in an older patient with more comorbidities and patent/diseased bypass grafts.
Preoperatively, a computed tomogram of the chest with angiography and three-dimensional reconstruction is performed to ascertain the exact location of the old bypass grafts and their relative location to the sternum (especially the left internal mammary artery).24 Coronary angiography and percutaneous coronary and graft intervention with drug-eluting stents are done as appropriate to optimize the revascularization as far as possible. Heart failure is controlled medically.
All patients need intraoperative transesophageal echocardiography and a pulmonary artery catheter with atrial and ventricular pacing wire placement capabilities, which should ideally be placed before incision. Accurate placement of external defibrillator pads is emphasized because internal paddles cannot be introduced in these patients.
All patients need peripheral cannulation for cardiopulmonary bypass. We prefer right axillary and percutaneous femoral venous cannulation. Appropriate arterial line placement is needed to facilitate need for circulatory arrest and antegrade cerebral perfusion if required.25 A standard upper hemisternotomy incision is made with a T into the right fourth intercostal space (Figs. 38-7 and 38-8). The anterior table split is performed with the use of an oscillating saw, whereas the posterior table split is performed on cardiopulmonary bypass using straight Mayo scissors starting from the top down (preferably from the assistant's side of the table). When the left internal mammary artery graft is close to the left side or the middle of the sternum, a preplanned one-third to two-thirds sternotomy to the right is performed. The right pleural space is widely opened. Only 5 to 10 mm dissection is performed underneath the left sternal edge, enough to facilitate the placement of the Kuros-Baxter® retractor. The rest of the mediastinal and aortic dissection is performed on cardiopulmonary bypass. Care is taken not to injure previous saphenous vein or radial arterial bypasses. It is not necessary to visualize the left internal mammary artery graft.
The upper hemisternotomy incision has been marked.
Peripheral cannulation for cardiopulmonary bypass.
We start core cooling to 25°C only after there is an ability to place an aortic cross-clamp. Moderate to deep hypothermia facilitates low flow states and reduces myocardial oxygen demand, which is important because the left internal mammary artery will continue to perfuse the heart for the duration of the operation. A retrograde coronary sinus catheter is placed through the right atrial appendage using TEE guidance. Usually, enough right atrial appendage is seen to place this catheter. Alternatively, a transjugular catheter can be placed before incision. After cross-clamping the aorta, 1 L antegrade cold blood cardioplegia is delivered through the aortic root. Thereafter, 500 cc of cold retrograde blood cardioplegia is used. Simultaneously, systemic hyperkalemia is achieved by instilling 40 mEq of potassium into the cardiopulmonary bypass. Systemic hyperkalemia will achieve diastolic arrest in the left anterior descending artery territory that is perfused by the left internal mammary artery distal to the aortic cross-clamp. All through the operation, frequent doses of antegrade (through the coronaries and grafts using perfusion canulae) and retrograde cardioplegia are delivered. Systemic hyperkalemia is maintained at a level of 6 to 7 mEq/L. This keeps the myocardium fairly quiescent during the procedure. Needless to say, heavy doses of potassium may leave the patient with severe hyperkalemia that may not be cleared in the setting of renal dysfunction. In addition to being judicious in such cases, it is imperative that the perfusion technologists be able to provide ultrafiltration as well.
The aortotomy is dictated by the location of previous bypass grafts. Although in some cases a standard oblique aortotomy can be made, most cases require a modified aortotomy such as a lazy S or a lateral vertical aortotomy (Fig. 38-9). The exposure should be adequate and an expeditious valve replacement is the key to success. We aim to keep the cross-clamp time under 60 minutes. In most cases, there will be continuous back-bleeding through the left main orifice from the open left internal mammary artery graft. During debridement and suture placement in the left coronary area, the bypass flows can be reduced or briefly turned off to facilitate exposure. Rewarming is started after the valve is seated. The aortotomy is closed in the standard fashion and a de-airing needle is placed before removal of the aortic cross-clamp. The heart often recovers spontaneous sinus rhythm. Defibrillation is achieved via the external pads if required. The de-airing and wean from cardiopulmonary bypass is as described before.
This is a lazy S oblique aortotomy keeping the grafts to the left.
Drainage tubes are always placed through the right pleural space. Subxiphoid placement is not possible and strongly discouraged. Rarely, when the right pleural space is completely fused, the silastic drain could be brought out in the supraclavicular area. It may be possible to place atrial pacing wires, but placement of ventricular wires is almost always quite difficult. We have routinely switched to the use of pulmonary artery catheter based pacing leads with good success. Closure is fairly standard, as described before, and care must be taken during the placement of wires on the left side of the sternum and the oblique lower wire (Fig. 38-10).
Final closure, also showing an occasional drainage tube in the supraclavicular space.
Our Experience with This Technique
Byrne et al26–28 first published the Brigham experience with reoperative minimal access aortic valve replacement in patients who had previously undergone coronary artery bypass grafting or other cardiac surgery and compared it with conventional surgery through a full sternotomy approach. Patients having a conventional full sternotomy redo AVR had more blood loss, more transfusions, and longer operations.
Our positive experience has encouraged others to pursue this technique. Dell'Amore et al29 report the suitability of this technique in their modest report of 10 patients, and Bakir et al30 report similarly.
As of 2008, the Brigham experience has grown to 146 patients, reported by Tabata et al31 The median times for cardiopulmonary bypass and aortic cross-clamp were 150 and 80 minutes, respectively, which are quite acceptable. The operative mortality was 4.1%.
This technique is clearly advantageous but has a fairly steep learning curve. When perfected, it can accomplish a successful operation, with lower mortality and morbidity in an older patient with multiple comorbidities who needs a redo AVR.