As Dick Cheney recovers from heart transplant surgery, questions are being raised about whether the former vice president is too old for a new heart.
Cheney, 71, who received the new heart Saturday at a hospital in Falls Church, Va., has been on the cardiac transplant list for more than 20 months.
Some medical centers will not perform a heart transplant on patient over 65, but other major centers will perform transplants on patients who are as old as 72.
In any case, transplants at Cheney's age are not unheard of: Last year 332 heart transplants were performed on people over 65, and according to the United Network for Organ Sharing, 14 percent of recepients are over the age of 65.
"Patients from 18 all the way up to 71 years old, are on the same national list and you're listed on the basis of medical urgency and then how long you've been waiting," said Dr. Jonathan Chen, an adjunct associate professor of surgery at Columbia University in New York.
ABC News chief medical editor Dr. Richard Besser said the average waiting time for a heart transplant at UCLA Medical Center is three to six months. But Cheney waited for more than 20 months to receive a new heart.
Experts differ on whether the 20-month wait is longer than normal.
"Twenty months, as an outpatient, [is] not [an] unusually long wait," Dr. Marrick Kukin, director of heart failure at St. Lukes Roosevelt in New York said.
But Dr. Keith Aaronson, medical director of the heart failure program at the University of Michigan said 20 months "is a relatively long waiting time for an LVAD recipient to wait for a heart transplant."
A Left Ventricular Assist Device, or LVAD, is an auxiliary pump, used when a patient's own heart is unable to pump effectively to meet the body's needs. It can be used as a bridge to get someone to transplant, a bridge while waiting to determine if someone will be a transplant candidate, or as an end in itself.
Aronson said Cheney might have waited because he may have had kidney dysfunction or pulmonary hypertension at the time his LVAD was implanted. These conditions are common in patients with advanced heart failure but sometimes improve after placement of an LVAD and make previously ineligible patients "acceptable candidates" for transplant, he said.
Because Cheney has had two prior heart surgeries, the immediate period after his heart transplant is critical. The majority of patients die from acute rejection, infection or complications of surgery.
If his heart should fail, Cheney would have two options: Undergo another transplant, which few centers would offer for a candidate of his age; or have another LVAD implanted, according to Dr. Mary Norin Walsh, director of cardiac transplantation at St. Vincent Hospital in Indiana.
Walsh said medical problems such as diabetes lung and kidney disease often disqualify patients in Cheney's age group. The fact that he was listed for cardiac transplantation, she said, assumes "that his sole medical problem is his heart."
Cheney will have to take anti-rejection drugs to prevent his immune system from attacking the new heart. In older heart transplant recipients, many cardiologists choose to minimize the use of anti-rejection drugs as much as possible to reduce the risk of infections. Cheney can also expect to undergo weekly heart biopsies to look for signs of rejection. Eventually, the frequency of the biopsies will taper off.
Cheney has had five heart attacks, the first of which was in 1978 when he was 37 years old, and the fourth in November 2000, after he and former President George W. Bush were elected to the White House. In 2001, Cheney had a pacemaker installed into his chest, and in September 2009, he underwent elective back surgery to treat lumbar spinal stenosis.
Walsh expects Cheney will have an easy recovery from the transplant partly because "he is used to heart surgeries."
Cheney's family said in a statement: "Although the former Vice President and his family do not know the identity of the donor, they will be forever grateful for this lifesaving gift.
"Former Vice President Cheney is thankful to the teams of doctors and other medical professionals at Inova Fairfax and George Washington University Hospital for their continued outstanding care."
Mitt Romney tweeted, "Ann and I send our thoughts and prayers to Vice President Cheney for a fast and full recovery."
Dr. Yana Svetlichnaya, an internal medicine resident at Northwestern University's McGaw Medical Center, contributed to this story.