Heart transplantation is an option for patients who have any of the following and who remain at risk of death and have intolerable symptoms despite optimal use of drugs and medical devices:
End-stage heart failure
Transplantation may also be indicated for patients who
Cannot be weaned from temporary cardiac-assist devices after myocardial infarction or nontransplant cardiac surgery
Have cardiac sequelae of a lung disorder requiring lung transplantation
The only absolute contraindication for heart transplantation is
Pulmonary hypertension that does not respond to preoperative treatments
Relative contraindications include organ insufficiency (eg, pulmonary, renal, hepatic) and local or systemic infiltrative disorders (eg, cardiac sarcoma, amyloidosis).
General contraindications to transplantation should also be considered.
All donated hearts come from brain-dead donors, who are usually required to be < 60 years and have normal cardiac and pulmonary function and no history of coronary artery disease or other heart disorders. Donor and recipient must have compatible ABO blood type and heart size. About 25% of eligible recipients die before a donor organ becomes available. Left ventricular assist devices and artificial hearts provide interim hemodynamic support for patients waiting for a transplant. However, these devices carry a risk of sepsis, device failure, and thromboembolism.
(See also Overview of Transplantation.)
Bridge and destination ventricular assist devices (VADs)
Implantable ventricular assist devices are being used to treat some patients who previously would have needed heart transplantation and patients for whom transplantation is contraindicated. These devices are usually used to assist the left ventricle as interim (bridge-to-transplantation) or long-term (destination) treatment in patients who are not candidates for transplantation. The devices are more and more compact, with the goal of having the battery compartment implanted under the skin as well and using induction charging. Infection, which may originate at the skin insertion site of the drive lines, is a concern. However, there are patients who have survived and have been well for several years after these devices were implanted.
Procedure
Donor hearts are preserved by hypothermic storage. They must be transplanted within 4 to 6 hours. Use of an in vitro pump system that modifies cell metabolism in the donor heart and thus may prolong transplant viability > 4 to 6 hours is under study. These pump systems more recently have allowed the use of cardiac grafts retrieved from donors after cardiac arrest.
The recipient is placed on a bypass pump, and the recipient's heart is removed, preserving the posterior right atrial wall in situ. The donor heart is then transplanted orthotopically (in its normal position) with aortic, pulmonary artery, and pulmonary vein anastomoses; a single anastomosis joins the retained posterior atrial wall to that of the donor organ.
Immunosuppressive regimens vary but are similar to those for kidney transplantation or liver transplantation (eg, anti-IL-2 receptor monoclonal antibodies, a calcineurin inhibitor, corticosteroids—see table Immunosuppressants Used to Treat Transplant Rejection).
Complications of Heart Transplantation
(See also Posttransplantation Complications.)
Rejection
About 50 to 80% of patients have at least 1 episode of rejection (average 2 to 3); most patients are asymptomatic, but about 5% develop left ventricle dysfunction or atrial arrhythmias. Incidence of acute rejection peaks at 1 month, decreases over the next 5 months, and levels off by 1 year.
Risk factors for rejection include
Younger age
Female recipient
Donor who is female or of African ancestry
Human leukocyte antigen mismatching
Possibly cytomegalovirus infection
Because graft damage can be irreversible and catastrophic, surveillance endomyocardial biopsy is usually done once/year; degree and distribution of mononuclear cell infiltrate and presence of myocyte injury in specimens are determined. Differential diagnosis includes perioperative ischemia, cytomegalovirus infection, and idiopathic B-cell infiltration (Quilty lesions).
Clinical manifestations of rejection can be classified according to onset, duration (see table Manifestations of Heart Transplant Rejection by Category
Cardiac allograft vasculopathy
The main complication of heart transplantation is cardiac allograft vasculopathy, a form of atherosclerosis that diffusely narrows or obliterates vessel lumina (in 25% of patients). Its cause is probably multifactorial and relates to donor age, cold and reperfusion ischemia, dyslipidemia, immunosuppressants, chronic rejection, and viral infection (adenovirus in children, cytomegalovirus in adults).
For early detection, surveillance stress testing or coronary angiography with or without intravascular ultrasonography is often done at the time of endomyocardial biopsy.
Treatment is aggressive lipid lowering
Prognosis for Heart Transplantation
Survival rates at 1 year after heart transplantation are 85 to 90%, and annual mortality thereafter is about 4%.
Pretransplantation predictors of 1-year mortality include
Need for preoperative ventilation or left ventricular assist devices
Cachexia
Female recipient or donor
Diagnoses other than heart failure or coronary artery disease
Posttransplantation predictors include
Elevated C-reactive protein and troponin levels
Within 1 year, death most often results from acute rejection or infection; after 1 year, death most often results from cardiac allograft vasculopathy or a lymphoproliferative disorder.
Functional status of heart transplant recipients alive at > 1 year is excellent; exercise capacity remains below normal but is sufficient for daily activities and may increase over time with sympathetic reinnervation. More than 95% of patients reach New York Heart Association class I cardiac status, and > 70% return to full-time employment.
