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Why did many early heart transplant patients die after surgery?

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Kidney transplant — transplant British surgeon Andrew Ready flushing a donated kidney during a transplant at Queen Elizabeth Hospital, Birmingham, England, 2006.

Many early heart transplant patients died primarily due to the body's immune system rejecting the transplanted organ. In this process, lymphocytes migrate into the heart muscle, damaging it and blocking the coronary arteries, which deprives the heart of its own circulation. Additionally, some lymphocytes secrete toxic antibodies that further contribute to organ failure.12

During the years immediately following the first human heart transplant in 1967, medical centers lacked adequate therapy to effectively combat this rejection. Furthermore, the heart is highly sensitive to a lack of blood supply, meaning it must be removed and implanted quickly, leaving a very narrow window for successful preservation.21

The field saw significant improvement in the 1980s with the introduction of cyclosporine, an immunosuppressant drug that allowed for better management of the immune response. This advancement, combined with better techniques for detecting and treating rejection, significantly improved long-term survival rates for transplant recipients.123