24 Cardiac Transplantation and Mechanical Circulatory Support Devices

Michael E. Bowdish, Michael R. Mill, Brett C. Sheridan

Cardiac transplantation developed as an outgrowth of research into heart preservation to allow safe open heart surgery. In 1961, Shumway and Lower published their seminal article describing the technique of orthotopic cardiac transplantation in a canine model, with successful functioning of the transplanted heart for several days. While Shumway was preparing to begin a human clinical trial of cardiac transplantation, Christiaan Barnard, a South African surgeon who had worked in the United States learning the techniques of immunosuppression and surgical transplantation, shocked the world in December 1967 by performing the first human-to-human heart transplant in Capetown. His patient lived for 18 days before succumbing to infectious complications. Shumway performed the first successful cardiac transplantation in the United States in January 1968, beginning what has become the longest ongoing program of cardiac transplantation in the world.

Activity in cardiac transplantation exploded after these initial successes. However, a dismal initial 1-year survival rate of 22% led most programs to abandon the procedure. Early transplant patients died of both immune rejection of the transplanted heart and infectious complications. Two major developments allowed surgeons and those caring for cardiac transplant patients to balance more successfully the complications of graft rejection versus systemic infection. The development in 1971 of the cardiac bioptome by Caves, combined with Billingham’s pathologic grading system for rejection, removed much of the treatment guesswork and permitted accurate diagnosis of rejection and rational strategies for maintenance immunosuppression and treatment of rejection. Cardiac transplantation improved rapidly again with the introduction of cyclosporine A in 1980. This calcineurin inhibitor dramatically reduced the incidence of rejection.

More recently, further investigation into basic mechanisms of transplant rejection resulted in triple-drug immunosuppressive regimens that used smaller doses of prednisone, azathioprine, and cyclosporine, allowing better rejection control with fewer infectious complications and adverse effects from these powerful immunosuppressive agents. Newer agents, such as tacrolimus, mycophenolate mofetil, and sirolimus, as well as the use of induction therapy, are now part of the antirejection armamentarium, and drugs continue to be developed.

Indications

Generally accepted indications for cardiac transplantation include the presence of end-stage heart disease not amenable to standard medical or surgical therapy, New York Heart Association (NYHA) class III or IV heart failure on maximal medical therapy, and an estimated 1-year life expectancy of less than 50%. As other therapeutic approaches have improved—from coronary artery bypass grafting to percutaneous interventions to advances in medical therapy for congestive heart failure—patients who need transplantation are generally older and sicker, and have multiple comorbidities. In addition, the spectrum of individuals considered for cardiac transplantation today has been broadened to include elderly patients, children, and newborns. The most common indications for cardiac transplantations in the adult population are cardiomyopathies and end-stage coronary artery disease (CAD). A minority of transplants are performed in patients with valvular heart disease, congenital heart disease, and as retransplants (e.g., for graft vasculopathy). In children the leading diagnoses are dilated cardiomyopathies and congenital heart disease (see Section VIII).

Potential transplant patients undergo an intensive screening process by a multidisciplinary team of cardiothoracic surgeons, cardiologists, transplant coordinators, social workers, dietitians, physical therapists, psychologists/psychiatrists, and financial counselors. The screening ensures not only that the patient needs the transplant but also that he or she is physically and mentally able to comply with the rigorous post-transplantation medical regimen and has the appropriate social support to undergo transplantation successfully.

Donors

Transplant donors are individuals who are brain dead but continue to have adequate cardiac function to temporarily support other organ function. Most die of catastrophic intracranial events or trauma. The hearts are carefully evaluated with respect to cause of death, need for cardiopulmonary resuscitation, and use of inotropic support; they undergo electrocardiography and echocardiography to ensure adequate ventricular and valvular function. In men aged older than 45 years, women aged older than 55 years, and patients with other risk factors for CAD, cardiac catheterization and coronary angiography are frequently performed. Donors undergo thorough serologic testing to rule out transmissible diseases, and their medical and social histories are evaluated.

Donor-Recipient Matching

Patients accepted for transplantation are placed on a national waiting list maintained by the United Network for Organ Sharing (UNOS). UNOS has a contract with the U.S. government to act as the organ procurement and transplantation network. Patients are placed on the waiting list by size, ABO blood type, medical urgency status, and waiting time. When a suitable donor is identified, UNOS generates a list that ranks potential recipients by distance from the donor hospital (to minimize the organ ischemic time during travel and implantation), size, ABO type, medical urgency, and waiting time. An organ is then offered to a prospective recipient’s transplant center. If the transplant physicians believe that the organ is suitable for their patient, arrangements are made to procure the organ and perform the transplantation. On occasion, a potential recipient is precluded from transplantation because of ongoing infection or another potentially reversible contraindication. If the initial center does not accept the organ, it is offered sequentially to all patients on the local list, followed by patients in ever-enlarging geographic circles until the nation is covered. Given the number of patients actively awaiting transplantation, the majority of hearts are placed within their local or regional areas. Other available organs are likewise matched with potential recipients.

Donor Procedure

After all the organs are placed, procurement surgeons arrive at the donor hospital, and a coordinated procedure allows simultaneous procurement of all usable organs, often including the heart, lungs, liver, kidneys, and pancreas and occasionally including the small intestine. The heart explant procedure depends on whether the heart alone will be used or whether the lungs will also be used separately or as a combined heart-lung transplant. After initial dissection of the aorta and superior and inferior venae cavae, placement of a cardioplegia cannula in the ascending aorta, and completion of the other teams’ initial dissections, the donor is systemically heparinized. The superior vena cava is tied off, the left atrial (LA) appendage is amputated, and the inferior vena cava is partially transected to decompress the heart and prevent ventricular distention. The aorta is then cross-clamped, and cardioplegia is infused while the heart is lavaged with ice-cold saline (Fig. 24-1).

Figure 24-1 Technique of biatrial cardiac transplantation.

Simultaneously, the other organs are flushed with their own preservative solutions and lavaged with cold saline. After completing the cardioplegia infusion, the superior and inferior venae cavae are transected. If only the heart is to be used, the pulmonary veins and pulmonary arteries are divided at the pericardium, and the aorta is divided. If the lungs are to be used, the left atrium is divided at the midatrial level, leaving enough cuff of the left atrium for cardiac implantation and cuffs around the pulmonary veins for lung implantation. The pulmonary trunk is divided at its bifurcation to leave enough length on the pulmonary arteries for the lung implantation. If a combined heart-lung transplant is planned, the two organs are resected en bloc by dividing the cavae, aorta, and trachea and dissecting the heart-lung block from its mediastinal attachments. The organs are then stored in ice-cold saline in multiple layers of plastic bags to ensure sterility, and they are packed in an ice-filled cooler for transportation to the transplanting center.

Recipient Procedure

Two approaches to orthotopic cardiac transplantation are widely used. In the traditional Shumway and Lower technique, a biatrial anastomosis is performed whereby the donor and recipient atrial cuffs are sewn together. This technique does not require separate caval anastomoses, and therefore saves time. An alternative technique, the bicaval technique, was developed in the 1990s and consists of sewing separate caval anastomoses. Purported advantages of this technique primarily relate to improved atrial function, decreased need for permanent pacing, and decreased tricuspid regurgitation. However, in an outcomes analysis of the UNOS database between 1999 and 2005, no survival difference was identified between recipients of bicaval versus biatrial orthotopic cardiac transplantation.

Biatrial Technique

The operation is performed through a standard median sternotomy using cardiopulmonary bypass with aortic and bicaval cannulation. The initial dissection and cannulation are performed while the heart is being transported to the recipient hospital. When the new heart arrives, cardiopulmonary bypass is instituted at moderate systemic hypothermia (~32°C), and caval tapes are secured around the caval cannulas. The aorta is cross-clamped and then divided just above the level of the aortic valve. The pulmonary trunk is divided above its respective valve, and the atria are divided at the midatrial level, with removal of the atrial appendages and preservation of the posterior atrial cuffs containing the pulmonary veins on the left and the cavae on the right. The donor heart is prepared by freeing the pulmonary artery from the aorta and the roof of the left atrium. The pulmonary venous orifices are interconnected to create a cuff for the LA anastomosis. Excess LA tissue can be removed to create a better size match for this anastomosis. The oval fossa of the donor heart is examined for a patent foramen ovale. If identified, it is closed. The LA anastomosis is then fashioned with a suture in a continuous running fashion. The suture line is begun at the base of the donor LA appendage, just above the recipient left superior pulmonary vein (see Fig. 24-1).

The donor right atrium is opened from the orifice of the inferior vena cava through the right atrial appendage and then sewn to the recipient atrial cuff. Next, the donor and recipient pulmonary trunks are cut to appropriate lengths. The pulmonary trunks are then anastomosed end to end with a running suture. Systemic rewarming is begun, and the donor and recipient aortas are trimmed and anastomosed with a running suture. The heart is de-aired, the suture line is secured, the patient is placed in a steep Trendelenburg position, and the cross-clamp is released, thus ending the donor heart ischemic time. During rewarming and reperfusion, the right side of the heart is de-aired, the caval tapes are removed, and the donor superior vena cava is oversewn. With rewarming and reperfusion, a spontaneous normal sinus rhythm usually develops. Regardless, temporary atrial and ventricular pacing wires are placed should temporary atrioventricular sequential pacing be needed postoperatively. After the onset of forceful ventricular contractions and completion of de-airing maneuvers, inotropic support is begun. Depending on the donor heart ischemic time and size, the recipient’s pulmonary vascular resistance, and the preoperative use of antiarrhythmic drugs (especially amiodarone), additional inotropic support or vasoconstrictive agents are sometimes necessary. The patient is then weaned from cardiopulmonary bypass. Heparin is reversed with protamine sulfate, and the heart is decannulated. After ensuring adequate hemostasis, chest drains are placed, and the sternotomy is closed.

Bicaval Technique

The operation is fundamentally the same as the biatrial technique. The differences in cardiectomy include developing the groove between the right and left atria to allow their separation. During excision of the heart, the superior vena cava is divided just above the level of the right atrium, and the inferior vena cava is divided just below the coronary sinus. After the aorta and pulmonary artery have been divided, a LA cuff is then created starting at the dome of the left atrium, carrying the incision inferiorly above the orifices of the right and left pulmonary veins (Fig. 24-2

Only gold members can continue reading. Log In or Register to continue

Share this:

• Click to share on Twitter (Opens in new window)
• Click to share on Facebook (Opens in new window)

Related

Related posts:

1. The History and Physical Examination
2. Syncope
3. Interventional Approaches for Peripheral Arterial Disease
4. Aortic Regurgitation

Stay updated, free articles. Join our Telegram channel

Join

Full access? Get Clinical Tree