c l i n i c a l f o l i o s : d i s c u s s i o n



Cardiac Transplantation

 

 

Related narrative: Heart Transplant, Donor Heart Procurement

Cardiac transplantation is a meticulously orchestrated event. It has proven to be an effective and life-saving option for patients with end-stage heart failure who deteriorate despite optimal medical management, and is currently the standard of care for these patients. Recipients of heart transplants are able to return to life as a productive citizens with dramatically improved quality and quantity of life.

Cardiac transplantation was first described by Carrel and Cuthrie in 1905 [1] in a heterotopic model that was ingenious for its time but far removed from clinical applicability. The development of the current technique of orthotopic transplantation is credited to Shumway and Lower [2] and was first performed by Bernard [3] in Cape Town, South Africa in the 1960s. Most of the early recipients of heart transplants died of rejection and the climate turned with the public's apprehension leading to the precipitous drop in the number of transplant centers. With the introduction of cyclosporin for immunosuppression in the mid 1980s there was a renewed enthusiasm for transplantation, as early and late outcomes imporved dramatically. One year survival rates in the early days of cardiac transplantation ranged from 20% to 30% and have improved to 85% at one year, 75-80% at 5 years and 65-70% at 10 years in the modern era [4].

Patients with dilated cardiomyopathy and ischemic cardiomyopathy make up the vast majority of people awaiting heart transplants. Candidates must meet eligibility requirements that vary from center to center, but generally involve being under a certain age (65 years old at New York Presbyterian Hospital), being free of malignant disease, and having the capacity for compliance with the complicated postoperative schedule of medications and follow-up appointments. Extensive physiologic and psychologic tests are also often performed. The candidates are typically New York Heart Association class III or IV heart failure and are maintained on a variety of cardioactive medications including diuretics, inotropes, angiotensin-converting enzyme inhibitors, digoxin and antiarrythmic medications when necessary. Sometimes it is necessary to maintain the patients in the hospital as they await transplant. This population of patients has a three year survival of less than 15%. As the gap widens between end-stage heart failure patients and the available organs, more and more patients deteriorate while awaiting an organ requiring in-patient support. When the patients can not be maintained on medications and no heart is available a final option is a ventricular assist device which mechanically supports the circulation until a heart becomes available. Currently such devices are approved as "bridges to transplant".

Donors become available when a patient meets brain death criteria which vary by state. Usually the organ procurement agency of the state verifies that the patient meets brain death criteria and the donor's next of kin express an interest in organ donation. Physicians, health care workers, members of the clergy and laypeople throughout the world have fully accepted that a person is dead when his or her brain is dead [5]. In the United States the principle that death can be diagnosed by neurologic criteria is the basis of the Uniform Determination of Death Act [6] although the law does not define any of the specifics of the clinical diagnosis. Guidelines for establishing brain death have evolved throughout the 1970's and '80's culminating in the American Academy of Neurology conducting an evidence based review and their recommendations for making the clinical diagnosis of brain death [7].

After eligibility is confirmed, evaluation of the heart is achieved via echocardiography to confirm that cardiac function is normal and that no significant valvular abnormalities exist. If the donor is over 50 years old, often a coronary angiogram will be performed to exclude the possibility of coronary artery disease. The donor heart is matched on the basis of ABO blood antigen compatibility and size through the United Network of Organ Sharing registry. The donor and recipient are generally within 20% body mass and body surface area. This is particularly important if the recipient has pulmonary hypertension, in which the donor size match becomes more important because the donor right ventricle must withstand a heavier workload. Harvesting is begun after all eligible organs have been placed by the various procurement agencies.

Procurement of the heart is usually performed in conjunction with a multiple organ harvest involving from two to four organ procurement teams. Both the abdomen and the chest are opened in the midline. The sternum is divided as is the pericardium, and the heart is inspected. All of the ventricular walls are evaluated for regional wall motion abnormalities and the external anatomy is inspected for anomalies. The coronary arteries are palapated for evidence of atherosclerotic disease. If the inspection is satisfactory then dissection in preparation for the harvest is begun. First the superior vena cava is encircled. Then the aorta is separated from the main pulmonary artery and encircled with umbilical tape. After the abdominal organs have been dissected free the patient is given 30,000 units of heparin and a cardioplegia cannula is placed in the aortic root through a u-stitch. The superior vena cava is occluded and the heart is vented by transecting the left inferior pulmonary vein and the inferior vena cava. The aorta is cross-clamped and the cardioplegia solution delivered into the aortic root to arrest the heart, which is subsequently removed and placed in a sterile bag with cardioplegia solution and transported on ice to the recipient hospital. The time from cross-clamping the aorta to leaving the donor hospital is typically 15 to 20 minutes.

Currently more than 15,000 patients per year could benefit from cardiac transplantation but only roughly 2,000 donor hearts are available annually [8]. One of the methods under investigation to close the gap is the development of permanent left ventricular assist devices. The REMATCH trial is evaluating the efficacy of LVAD versus medical management of end-stage heart failure in patients who are not transplant candidates. Other solutions include xenotransplantation, or the use of non-human hearts, and perhaps in the more distant future organ cloning. In the meantime however attempts to increase the donor pool by public education and awareness are critical.

References:

1. Carrel A, Guthrie CC: The transplantation of veins and organs. Am Med 10:1101, 1905.

2. Lower RR, Shumway NE. Studies on orthotopic homotransplantation of the canine heart. Surg Forum 11:18-23, 1960.

3. Barnard CN: What we have learned about heart transplants. J Thorac Cardiovasc Surg 56:457-68, 1968.

4. Spann JC, Van Meter C. Cardiac transplantation. Surg Clin N Am 78(5):680-90, 1998.

5. Wijdicks EFM. The diagnosis of brain death. N Engl J Med, 344(16);2001:1215-21.

6. Uniform Determination of Death Act, 12 Uniform Laws Annotated (U.L.A.) 589 (West 1993 and West Supp. 1997).

7. The Quality Standards Subcommittee of the American Academy of Neurology. Practice parameters for determining brain death in adults (summary statement). Neurology 1995;45:1012-14.

8. Evans RW. The actual and potential supply of organ donors in the United States. Clin Transplant 329-341, 1990.


This page was last modified on 16-Aug-2001.