Hospital heart transplant centers that adopt a scoring method can greatly increase the chance recipients will be alive one year later and thereby more efficiently use scarce donor hearts, say cardiac surgery researchers at Johns Hopkins Medical Institutions.
"If you want to enhance post transplant survival, you'd shift organs from some of the people we've identified with multiple risk factors for poor outcomes to patients with a better chance," explained Ashish Shah, MD, Surgical Director of Johns Hopkins' lung transplant program and one of the study's authors.
"If you think about this as a limited resource, you have to be careful with offering transplants when we don't have enough hearts to go around," Shah said in a telephone interview. In the published paper, the authors say they "surmise" that their index "could serve to drive clinical decisions regarding allocation of marginal organs and may prove especially useful in an era of increasing ventricular assist device (VAD) utilization."
Current practice evaluates eligibility based on how sick a patient is and how long they've been on a waiting list, and other aspects of a patient's condition that are educated guesses. The new tool gives transplant specialists more scientific basis for choosing their candidates.
The researchers evaluated 21,378 patients who received a donor heart between 1997 and 2008 in the United Network for Organ Sharing database and tracked them to December of 2010. They then scored numerous patient variables and conditions that might have influenced their survival and formatted them in a 50-point scoring system that allocated points to each factor.
For example, the patients who needed temporary circulatory support prior to transplant had the highest risk score of 7 points. Use of a ventricular assist device, other than the more common HeartMate II, counted 5 points, although reasons why are unclear.
A bilirubin count of 4 or higher was weighted at 4 and having dialysis between wait listing and transplant was scored at 3. Being female and being African American and being over age 60 each add three points.
When counted up, those patients who had conditions that tallied 20 points or more had a more than 50% chance of dying within one year, they found.
Those with the lowest scores, between zero and 2, had a 92.5% chance of one-year survival.
The research team was led by John V. Conte, MD, director of Johns Hopkins Heart Transplant program. Their findings are published in the September issue of the Annals of Thoracic Surgery.
According to the UNOS database, there were 3,196 people waiting for a heart on Monday across the country, but a shortage of donor hearts means that only about 2,000 transplants will be performed this year. For transplants performed between 2006 and 2007, 12% did not survive the full year, 19% did not survive three years and 25% did not survive five years.
Shah said that in general, heart transplant centers determine candidate eligibility based on how long a patient may have been on a transplant waiting list, and how sick he or she might be.
To exclude certain patients, centers and professional societies have a general agreement on indications and contraindications, but in reality, any transplant program can and will transplant any patient it sees fit.
For example, patients with cancer diagnosed in the last five years, end stage liver disease, lung disease, or kidney disease are theoretically precluded from receiving a heart. So are active smokers and active users of illegal drugs. "But there are no hard and fast rules," Shah explained.
"The only caveat is that if your outcomes are lousy, you are held to a standard as far as the outcomes are concerned, based on a modest amount of expected survival for your program at one year, and other incremental time points at less than a year," he said. If a center's survival rates are more than 1.5 standard deviations lower than expected, "your program will be scrutinized" and possibly closed by federal payers.
Today, he said, heart transplant centers make these decisions on a case-by-case basis. "We have learned almost anecdotally what works and what doesn't, but the purpose of using a large database like this with rigorous follow up is that we can actually put some numbers to this risk."
Now, he says, transplant program leaders will have to ask themselves an important question: "If we knew this person would have a 50% chance of surviving one year, would we still have done it?"
There is, of course, a trade-off, Shah said. "The post-transplant outcomes would be better, but wait list mortality would be higher. The people you didn't give the heart to would likely be dead."
However, he added, "this is the first step to say the field needs to start measuring things, to look at outcomes critically and then decide what's acceptable."