In This Article
- A scarcity of organs leads to death for patients waiting for heart or lung transplants
- Warm perfusion allows physicians to carefully assess marginal organs
- New, effective treatments for hepatitis C opens the door for use of organs that were previously discarded
As of February 2018, nearly 4000 patients were on the United Network for Organ Sharing waiting list for heart transplants, and nearly 1400 patients were waiting for lung transplants. Twenty Americans die every day waiting for transplants. David D’Alessandro, MD, Mauricio Villavicencio, MD, MBA, and cardiac transplant colleagues at Massachusetts General Hospital are aggressively researching and developing solutions to this organ shortage crisis. The team is increasing the number of hearts and lungs available for transplant by using organs that would have previously been rejected, and improving methods of assessing organs that do become available.
Through these novel approaches combined with an expanded capacity in the transplant center, the Mass General team performed a hospital-record 40 heart transplants in 2017. At the same time the transplant volume has increased the MGH Heart Transplant Program has achieved record low waitlist mortality indexed to person-years on the transplant list (8.2 per 100 person-years on the list much lower than the national average of 13.8 per 100 person-years).
Gregory Lewis, MD, medical director of Heart Transplantation and section of Heart Failure at Mass General, attributes improved outcomes on the waitlist to a rigorous evaluation process and concerted efforts by a multidisciplinary team to improve management of advanced heart failure patients who are awaiting transplantation.
Warm Perfusion Boosts Transplant Activity
Mass General is one of the few medical centers using the Organ Care System by TransMedics to assess hearts and lungs ex vivo before transplantation. The device has several advantages:
- Surgeons can preserve organs while they carefully assess them, so some organs that might previously have been rejected are found to be suitable
- Higher-risk recipients can be selected, such as those with mechanical circulatory support
- The system is portable, which allows hearts to be transported farther than with cold storage
The Organ Care System is a miniature bypass machine containing a pump, an oxygenator and a heat exchange unit. The machine connects to the aorta. The inferior and superior vena cava are closed off to direct the venous return to the right ventricle. A tube in the pulmonary artery also connects to the circuit. This arrangement provides an accurate measure of coronary blood flow: the amount of blood flow through the pulmonary artery tube is the same amount of blood flowing to the coronary arteries. A drainage system collects spilled blood that comes from cut surfaces.
“You can watch the heart beat, you can pace it with external electrodes, and you can get measurements of aortic pressure and coronary blood flow,” says Dr. D’Alessandro.
The heart can be treated with pharmaceutical agents to control some of these parameters. In addition, hearts can be assessed by its utilization of lactate. A heart in a normal condition uses lactate as an energy source. If the lactate in the system drops over time, the heart is functioning normally.
“With cold storage, you keep the heart from dying, but there is no electrical activity,” notes Dr. Villavicencio. “With ex vivo perfusion, nutrients and oxygen are carried to the heart while it is transported. Clinically, this is much better.”
He adds that Mass General also has experience with warm perfusion of lungs. The lungs are ventilated, and parameters such as oxygenation and airway pressure are monitored.
Mass General recently participated in the EXPAND clinical trial, a 20-center trial of the Organ Care System prior to heart transplantation. Unconventional inclusion criteria for heart donors included:
- Age ≥ 55
- Down time of ≥ 20 minutes with stable hemodynamics
- Left ventricular ejection fraction ≥ 40 ≤ 50%
- Angiogram with luminal irregularities without significant CAD
- Carbon monoxide poisoning with good cardiac function
- Alcoholism with good cardiac function
- Diabetes combined with negative angiogram for CAD
Results from this trial will be published soon.
A Surprising Source of Donors
Dr. Lewis and members of the Liver Transplant Team, including Raymond Chung, MD, and Emily Bethea, MD (international experts in the treatment of hepatitis C), developed an Institutional Review Board Approved Protocol to treat patients receiving hearts from donors with hepatitis C at Mass General. The cardiac transplantation team at Mass General has now successfully implanted five patients with hearts from donors with hepatitis C. With minimally toxic drugs for hepatitis C now available, it is possible to implant a heart from a donor with hepatitis C to meet the patient’s immediate needs and cure the infection after.
“This protocol has expanded the pool of donor hearts available to our patients and has resulted in our ability to quickly transplant patients who are in urgent need of a new heart” said Dr. Lewis.
“You can imagine the mental hurdle you are faced with, to knowingly give a patient hepatitis C at a time when the patient is going to be immunosuppressed,” says Dr. D’Alessandro. However, because patients on the waiting list have such a serious risk of death, he says, “we thought it was worth the risk.” Dr. Villavicencio added, “Many of the donors who are positive for hepatitis C are otherwise very good potential donors.”
A Team Approach Leads to Improved Outcomes
Mass General takes a multidisciplinary approach to organ selection by having cardiac surgeons work closely with cardiologists. Heart transplantation is a truly multidisciplinary effort and "we are fortunate to have a highly dedicated team caring for this growing number of patients before, during, and after transplantation," said Dr. Lewis. The multidisciplinary transplant team also includes social workers, pharmacists, nutritionists and several other specialists as needed. Mass General is also the only hospital in the region that considers patients for dual heart/lung transplants. These innovations help the team at Mass General achieve its dual goals of providing the highest quality patient care and being conscientious stewards of a fixed organ supply.