A new lease on life:

Dalhousie researchers find key to long-term survival of heart transplant patients

Heart transplant patients get a new lease on life – but not for as long as they and their doctors would like. Early transplant results are excellent: more than 90 per cent of patients are doing well one year later. But after several years, heart function begins to decline. About 50 per cent of patients experience failure of their transplanted hearts within 10 years.

“Advances in immune suppression have improved short-term survival, but long-term survival hasn’t changed much in 20 years,” says Dr. Greg Hirsch, QEII heart surgeon and head of the Division of Cardiac Surgery at Dalhousie Medical School. The problem is called ‘chronic rejection,’ and Dr. Hirsch is working with Dr. Tim Lee, professor in the Department of Microbiology & Immunology, to solve it.

Over the past decade, Drs. Hirsch and Lee have discovered how chronic rejection works – causing an international stir by overturning the prevailing views about this phenomenon.

“The transplant patient’s immune system sends killer T-cells to the donor heart, because it’s a foreign object,” explains Dr. Lee. “Current immune suppression therapies don’t affect these T-cells, which attack the coronary arteries, prompting other cells to come repair the damage. The cells clog the coronary arteries, slowing blood flow and depriving the heart of nutrients. Then the heart starts to fail.” The only solution is another new heart – but outcomes for second transplants tend to be poorer and the supply of donor hearts is limited.

The team recently discovered another piece of the puzzle. They've identified key mechanisms that help the killer T-cells resist immune suppression drugs. “Now we have a target for a new therapy,” Dr. Hirsch says. “The next step is to develop and test approaches that will derail these mechanisms and stop chronic rejection.” Then heart transplant patients could expect to live many more years with their new hearts.

Chair of the Cardiovascular Research Group, Dr. Hirsch is a key leader in the move to establish a Centre for Excellence in Heart Function Studies at Dalhousie Medical School.