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Heart transplants are performed in patients with heart failure due to weak heart muscle. In most of these patients, the cause for the weak heart muscle is either unknown, due to a prior viral infection of the heart or due to blocked coronary arteries. Rarely, heart transplants are done on patients who have weak heart muscle due to valve disease or congenital heart disease.
A heart transplant is performed when all other options for treatment have been exhausted. Included in this scenario are patients with blocked coronary arteries that are not amenable to a bypass operation or in whom severe, symptomatic heart failure persists despite a bypass operation. Similarly, patients with weak heart muscle due to valve or congenital disease may need a transplant if symptoms of weak heart muscle persist after surgical correction of the valvular or congenital problem. Patients in whom the weak heart muscle is due to a virus or unknown cause generally don't have any surgical options available to them (see below).
When we refer to persistent symptoms, it means that the symptoms continue despite optimization of treatment with heart failure medications. In addition to the presence of symptoms, a special type of stress test is performed to measure maximal oxygen consumption before the final decision is made regarding a transplant. Patients whose maximal oxygen consumption exceeds a certain value can generally get by without a transplant.
Some patients with seemingly intractable heart failure can improve markedly by being hospitalized and given intravenous medications guided by a special intravenous catheter that measures pressures within the chambers of the heart. Once the recorded pressures fall within the normal range, the intravenous medications are changed to oral medications and the patient is discharged home.
Since the supply of donor hearts is quite limited, transplant specialists generally pursue any alternative before listing a patient for a transplant. In addition, transplants are generally not performed on elderly patients (over the age of 65 to 70 years), patients in whom other medical conditions are expected to limit their lifespan and in patients who cannot be counted on to comply with the demanding medical regimen required after a transplant.
Some patients awaiting a transplant may be well enough to remain at home. Others may be critically ill and unable to get out of the intensive care unit. These patients often require intravenous medications to support the heart muscle. Some of these patients require an intraaortic balloon pump or a ventricular assist device. These are mechanical devices placed into the patient's circulation that pump the blood to the body to assist the failing heart. A priority list for transplants is established based on how sick the patient is. Patients unable to get out of the intensive care unit are obviously listed as the highest priority.
After a transplant, the patient must take medications to prevent rejection. Rejection is a process by which the patient's immune system attacks the foreign tissue of the transplanted heart. This results in weakening of the transplanted heart muscle and narrowing of the transplanted coronary arteries (known as graft atherosclerosis). The patient then develops symptoms of heart failure.
Medicines to prevent rejection usually include prednisone, azothiaprine and cyclosporine. Since these medications work by suppressing the immune system, one must be alert for any signs of an infection-especially by unusual organisms. Antibiotics such as sulfamethoxazole-trimethoprim may be given chronically to help prevent infections.
Pravastatin is a cholesterol lowering medicine that prevents the transplanted arteries from narrowing. It accomplishes this through an anti-inflammatory effect, as well as by lowering the cholesterol level. Diltiazem, a calcium blocker, also helps prevent narrowing of the transplanted arteries.
DETECTING AND TREATING REJECTION
Transplant patients undergo periodic cardiac catheterizations to obtain a biopsy to screen for rejection of the heart muscle. This is far more reliable than noninvasive tests such as echocardiograms or waiting for symptoms of heart failure to occur. Coronary angiography and intravascular ultrasound are also performed to see if the transplanted arteries are narrowing.
Episodes of rejection may be treated by increasing the dose of prednisone or adding additional medications, depending on the severity of the rejection.
More than eighty percent of heart transplant recipients survive one year and fifty percent survive 5 years. A transplant would be recommended in an eligible patient when a worse life expectancy is anticipated without a transplant.
Some experimental procedures offer alternatives to some people who may not want a transplant or who may be ineligible for a transplant. Transmyocardial laser revascularization may be an alternative for some people with inoperable blockages in their coronary arteries. Heart reduction surgery has not been shown to be helpful in well conducted scientific studies. Left ventricular assist devices can be used temporarily or permanently in patients with severe, intractable heart failure.
Combined transplantation of the heart and both lungs can be performed for people whose lungs were damaged by their heart disease as well as for people with primary disease of the lungs, such as cystic fibrosis. An alternative for people with primary lung disease and a healthy heart is a single lung transplant.
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