Aortic Valve Replacement via Minimal-Access Complete Sternotomy

Abstract

Minimally invasive approaches to the chest for aortic valve replacement have been proposed recently in an attempt to reduce postoperative pain, length of hospital stay, and scarring. An alternative approach entailing a minimal skin incision and a complete median sternotomy is presented herein. This technique combines the advantage of limited cosmetic impact with the pattern of postoperative pain and the ventilatory mechanics typical of the sternotomy, which enables extubation upon skin closure and early discharge from the hospital.

Recently, a variety of minimally invasive techniques to approach the diseased aortic valve have been proposed, ranging from right thoracotomies ^1–4 to transverse or partial median sternotomies, ^5–8 and even partial “complex” sternotomies. ^9–11 Despite the obvious cosmetic advantage of a small skin incision, none of the reported techniques has proved superior to the standard complete median sternotomy in limiting postoperative complications and thereby accelerating postoperative recovery. ¹² On the contrary, all these alternative methods have the potential for substantial chest-wall instability due to sternal dehiscence, overriding, or fracture. We describe a safe technique for aortic valve surgery that combines the cosmetic benefit of a limited skin incision with the advantages of a complete median sternotomy. This is the same method which, 2 years earlier, we described in conjunction with repair of congenital heart defects. ¹³

Surgical Technique

The patient is placed in the supine position, as for a standard median sternotomy. A midline skin incision is started 2 cm below the angulus sterni and is extended to a maximum length of 8 cm (Fig. 1). An additional 1- to 1.5-cm skin incision is made 2 cm below the xiphoid process (Fig. 1). The soft tissues over the body of the sternum and manubrium are undermined to expose the suprasternal notch and the xiphoid process. A complete median sternotomy is performed using an oscillating saw, starting from the body of the sternum and extending above and below the sternum during alternate retraction of the soft tissue flap. A Finocchietto retractor is inserted and the thymic fat is removed. The pericardium is entered through a right paramedian vertical incision, and traction sutures are placed on the free edges to improve exposure of the right atrial appendage and the interatrial groove.

Fig. 1 This drawing shows the length and position of the midline skin incisions relative to the anatomy of the sternum and chest wall.

A pursestring suture for arterial cannulation is placed in the distal portion of the ascending aorta, and another is positioned on the right atrial free wall below the atrial appendage for venous cannulation. The aorta is cannulated using a 24-F wirereinforced arterial cannula (Medtronic, Inc., Medtronic DLP; Grand Rapids, Mich). This cannula is chosen for its small size, so that it can be introduced through the primary incision, and for its flexibility, because it can conform easily to the soft-tissue flap at the upper end of the wound. In addition, the cannula is equipped with an obturator-dilator, which allows prompt insertion into less accessible portions of the ascending aorta. Venous cannulation is performed with a right-angled, metal-tipped, 28-F cannula (Medtronic). With the tip protected by a glove, the cannula is tunneled through the subxiphoid skin incision and inserted perpendicular to the right atrial free wall to ensure unimpeded venous drainage (Fig. 2). Normothermic bypass is begun, and a vent line is positioned through the right superior pulmonary vein.

Fig. 2 This view shows the opened pericardial sac and the position of the cannulae for cardiopulmonary bypass. Note the inferior, right-angled, metal-tipped caval cannula, which, along with its tourniquet, has been tunneled through a separate subxiphoid port. This incision will later hold the chest tube for pericardial drainage.

After the heart is emptied, the right atrium is retracted cephalad, and a coronary sinus catheter is inserted, with transesophageal echocardiographic guidance, for retrograde delivery of cardioplegic solution. The aortic cross-clamp is applied through the main incision, and the heart is arrested by means of retrograde cardioplegia. A transverse circumferential aortotomy is performed to improve exposure of the aortic root, and cardioplegic solution is injected antegrade directly into the coronary ostia. Aortic valve replacement is then performed as it would be in the course of a standard median sternotomy. Maintenance cardioplegic solution is administered through the coronary sinus. After repair of the aortotomy, de-airing is performed via the ascending aorta and vent line. The adequacy of de-airing is evaluated by transesophageal echocardiography. Cardioversion is achieved by direct application of pediatric paddles. The cannulae are then removed, after which a pericardial chest tube is inserted through the subxiphoid skin incision. The sternotomy is closed with stainless steel wires, and the soft tissue is closed with running absorbable suture. The patient is extubated in the operating room or shortly thereafter in the recovery room. After 12 hours of observation, the patient is admitted to a hospital room, and discharge from the hospital is planned on postoperative day 3.

Discussion

The large number of reports published during the past 2 years with regard to minimally invasive techniques for cardiac operations underscores the explosion of interest in less invasive surgical approaches. ^1–12 The general hypothesis underlying these techniques is that smaller incisions and limited dissection may attenuate intraoperative trauma and complications, thereby hastening postoperative recovery and minimizing procedure-related costs. In addition, patient satisfaction may increase in association with smaller surgical scars and more rapid recovery. As yet, no controlled clinical trial has proved this hypothesis, aside from a single, nonrandomized, retrospective study involving a small cohort of carefully selected patients. ¹⁴

Aortic valve repair or replacement by a right parasternal thoracotomy is 1 such method that has been proposed; ¹ however, this requires resection of costal cartilage, which may lead to chest wall instability and increased pain for the patient. Reimplantation of the costal cartilage ⁴ and a standard right anterior thoracotomy using custom-fashioned rib-retractors ^2,3 have also been described. However, these methods have the disadvantages of limited exposure, frequent need for femoral artery cannulation, ^1–3 and the attendant risk of life-threatening complications. ¹⁵ In addition, the cosmetic advantage of a 10- to 12-cm, right parasternal, asymmetric scar is unclear. ^1–4 Partial sternotomy approaches have been adopted most frequently. When used for aortic valve surgery these approaches all share a limited (10- to 12-cm) median skin incision, positioned in the upper, middle, or lower portion of the sternum. Aside from the technique entailing an upper skin incision starting at the suprasternal notch, ⁸ which is of questionable cosmetic advantage, these other incisions are certainly preferable to the 18- to 20-cm incisions used in standard median sternotomies.

Partial sternotomy approaches to the aortic valve vary, depending on the way the sternum is divided, and are colorfully identified as j, ⁵ J, reversed C, ^5,7,8 reversed j, ¹⁶ mini-T, ^10,11 and reversed Z sternotomies. ⁹ Partial sternotomies, however, all share the same disadvantages in comparison with the median sternotomy: greater potential for sternal stump dehiscence, overriding, and fracture. These serious complications are already being reported, ⁸ possibly nullifying the expected advantages of less invasive approaches. Another shared aspect of partial sternotomies is that, although conversion to a complete sternotomy may be relatively simple, it will result in complex sternal fractures that are difficult to stabilize. Moreover, there is no evidence that any of these alternative approaches actually offers greater control of postoperative pain or faster recovery. ¹²

The method proposed herein was originally tested for repair of simple septal defects (atrial, ventricular, and atrioventricular) in children and adults. ¹³ The encouraging results prompted us to extend its use to elective aortic valve procedures. Among the advantages of a limited (8-cm) skin incision with a complete median sternotomy are the cosmetic result (comparable to that of a partial sternotomy), the ease of execution with no need for custom-designed surgical instruments, and the exceptional versatility of the incision (mitral valve and coronary operations can also be performed with use of this technique). Conversion to a “standard” approach is as simple as a skin incision, and chest stability after closure is comparable to that after a median sternotomy. Due to the limited dissection of the mediastinum and minimal spreading by the chest retractor, one can speculate that postoperative pain may be reduced. Rapid postoperative recovery has invariably been observed, including extubation shortly after skin closure and discharge from the hospital on or before the 3rd postoperative day.

In conclusion, a minimal-access complete sternotomy approach offers a safe and low-cost alternative to a partial sternotomy, enabling less invasive aortic valve operations.