Surgical Technique to Facilitate Explantation of Mechanical Circulatory Support Devices

LVADs, BiVADs, and TAHs Before Heart Transplantation

Abstract

Thoughtful preparation of the surgical field at the time of initial mechanical circulatory support (MCS) implantation has the potential for decreasing operative time and surgical risk of subsequent heart transplantation. It sets the stage for expeditious, safe sternal reentry, and identification of structures necessary for initiation of cardiopulmonary bypass (CPB).

Heart transplantation after previous implantation of Mechanical Circulatory Support (MCS)¹ can be tedious, time consuming, and maybe associated with considerable risk. Identification of landmarks in the mediastinum is essential for cannulation. However, dissection may be difficult, or prolonged, potentially requiring emergent cardiopulmonary bypass (CPB), using alternative cannulation routes, or even extending donor organ ischemic time.

Prolonged CPB, coagulopathy, and additional surgical repair of injuries set the stage for undesirable consequences: protracted operation, use of blood products, end-organ dysfunction, need for temporary MCS, extended ventilation, ICU stay, and hospital stay. This may result in increased utilization of resources, cost, and poor outcomes.

Techniques for the protection of MCS and internal organs have been described and used both for adults and pediatrics.^1,2 An updated technique for preparation of mediastinal structures and MCS at time of implantation is described. It facilitates MCS explantation and heart transplantation.

Technique

The technique to facilitate mediastinal reentry uses three components: 1) blue polyisoprene bands (BBI; Bioseal, Placentia, CA), 2) Gore (polytetrafluoroethylene (PTFE)) pericardial membrane substitute (20 × 15 cm × 0.1 mm, W. L. Gore & Associates, Flagstaff, AZ), and 3) Surgical grade silicone membrane 0.060 inches thick (Bentec Medical, Woodland, CA). The blue, polyisoprene bands (BB) have to be prepared in advanced. They are placed into standard sterilization packaging and undergo gas sterilization (Sterrad 100S Sterilization System; Johnson and Johnson, Irvine, CA) for later use. This technique has been described previously.³

After MCS device implantation, the surgical technique for future device explantation and transplantation starts before chest closure. Blue bands are loosely placed circumferentially around the aorta and inferior vena cava (IVC; Figure 1). The entire length of each vascular structure is covered to avoid adhesion formation, minimizing the necessity for dissecting the structure during the subsequent operation. During left ventricular assist device (LVAD) placement, some surgeons may elect not to place a BB around the superior vena cava (SVC) to simply dissect at the time of heart transplantation. However, when utilizing a total artificial heart (TAH), the use of a BB around the SVC is recommended as well. The main advantage is that no adhesions form around these latex free bands. The BB for the SVC may be cut narrower to avoid possible SVC stenosis. Furthermore, the blue color facilitates identification of vascular structures and aids in timely preparation for cannulation. Care should be taken not to place the BB too tight around the vascular structures. Several centimeters of excess BB are left on top of the vascular structure and the free ends clipped together with Surgiclips (Autosuture Premium Surgiclip II M-9.75; US Surgical, Norwalk, CT). The upper part of the most distal BB around the aorta is sutured down near the innominate vein to protect it from injury during reentry. A separate piece of BB can be the placed between the aorta and the right atrium. On occasion, a BB is placed around the pulmonary artery or placed between its posterior wall and a protruding (large) left atrial appendage.

Figure 1: Blue bands loosely placed around superior vena cava (SVC), inferior vena cava (IVC), and aorta.

Before the MCS device is positioned into the mediastinal cavity or preperitoneal cavity, a 0.1 mm thick PTFE sheet is secured at the medial aspect of the mediastinum, by suturing the edges of the sheet to areas lateral to the left pulmonary veins (for TAH only). During chest closure, one or two additional sheets are used to cover the entire devices (LVAD, biventricular assist device [BiVAD], and TAH), as well as the right atrium and both venae cavae (Figure 2). The sheet over the right atrium can be tacked down with interrupted sutures to the pericardium near the venae cave to prevent migration. Drainage tubes are placed at this time in a routine fashion.

Figure 2: PTFE 0.1 mm sheets over a total artificial heart (TAH).

In the case of LVADs and BiVADs, additional sheets are used to cover the driveline and the outflow graft separately. The edges of the various sheets are clipped together with surgiclips. If appropriate, they are also clipped to the BBs already in place. For better drainage, several slit openings are cut into the sheets to allow fluid or blood to reach the mediastinal drainage tubes.

A segment of surgical silicone membrane 1 cm wide and as long as the sternum is the cut and placed above the sternal wires before sternal closure (Figure 3). When the sternum is reapproximated, care must be taken to make sure that the silicone membrane remains between the sternal wires and underside of the sternum and not be displaced between the blades of the sternum (Figure 4).

Figure 3: Silastic membrane (1 × 25 cm) being placed between sternal wires and underside of the sternum before sternal reapproximation. Arrows show direction for placement.

Figure 4: Computed tomographic scan showing cross section of sternum and proper position of the silastic membrane above the sternal wires and under the sternum.

At transplant, a redo lateral oscillating blade saw is used to perform the sternotomy in a routine fashion at a level above the silicone membrane. The membrane serves as the first protective layer, which can be easily removed, as no adhesions form around it. The BBs are identified around the encircled vessels.

The clips on the BBs are removed, and a small hole is cut into one end. An umbilical tape is threaded through that hole and subsequently placed around the vessel, as the BB is removed. As there are no adhesions around the encircled vessels (aorta, IVC, SVC), minimal dissection is required and CPB can be initiated expeditiously, if required. The PTFE membranes are then removed from around the device the anterior surface of the heart or TAH. This facilitates exposure of the device as adhesions are minimized.

Comment

This technique has been used for 3 years. No change in preoperative or postoperative prophylactic antibiotics has been done. The last 50 patients who have undergone this technique and transplanted have been reviewed retrospectively. One year data are available in 43 patients. Of the 50 patients, no cultures were performed in 23. The remaining 27 patients, two grew Staphylococcus epidermidis, considered a contaminant. One patient grew Staphylococcus aureus from driveline and LVAD pocket. He was treated with antibiotics long-term. One patient with previous aortic dissection and endocarditis grew one colony of Mycobacterium kansasii from the TAH aortic conduit and was treated with antibiotics. None of the 50 patients experienced mediastinitis, infection-related complications or death. The simultaneous use of BB, PTFE sheets, and silicone membrane has expedited the reentry procedure for transplantation and also provide a level of mediastinal structure protection.

The use of thicker PTFE sheets (>0.1 mm) has been associated with adhesion and scar tissue formation.

Besides the BB properties of preventing adhesion formation, additional benefits include its color, which facilitates easy and rapid identification of vital structures and are inexpensive. The technique of inserting umbilical tapes into the edge of the BB before its removal facilitates rapid access to the aorta, IVC, and SVC and therefore aids in timely and easy cannulation for CPB³ and it might decrease the operative risk for the patient. The average time for reentry, device dissection and mediastinal dissection, institution of CPB, and cardiectomy for subsequent heart transplantation can be reduced. This is in contrast to our experience that redo sternotomy in device patients can be significantly prolonged and tedious.

Downsides for this technique are the operation is prolonged for a few minutes; foreign material is left in the mediastinum; and the cost.

This technique can be used in other patients where a possible reentry is planned like a bridge to decision and in some destination LVAD cases, as reoperations for device exchanges, cross-over to transplantation candidacy, and other reasons are not that uncommon.⁴