Pulmonary arterial hypertension (PAH) is the only major diagnostic indication for transplantation that is not a parenchymal pulmonary process.
Insights from a new paper outline the unique considerations and management approaches for patients with pulmonary arterial hypertension (PAH) undergoing lung transplantation.
Currently approved treatment options for Group 1 PAH, although effective, are not curative options for patients. In patients with end-stage disease, lung transplantation has been posited as an option to improve survival and health-related quality of life. PAH is the only major diagnostic indication for transplantation that is not a parenchymal pulmonary process.
These findings published recently in CHEST.
Lung transplantation is generally considered effective, with registry data from the International Society for Heart and Lung Transplantation and the United Network for Organ Sharing showing an estimated 90% of recipients alive 1 year post transplant, 61% alive 5 years post transplant, and 33% alive 10 years post transplant.
However, patients with PAH often face various challenges throughout the perioperative period, creating complexities in using this approach for these patients. Success of lung transplantation in the United States depends on survival on the waitlist, getting a deceased donor transplant faster, and 1-year posttransplant survival.
“Assessing the success of a lung transplant program using these 3 metrics may unintentionally be a disincentive for smaller or underperforming centers to consider patients with PAH as transplant candidates,” wrote the researchers. “Thus, it is important to consider the experience of the center in doing transplantation for patients with PAH when referring, so that patients are not denied solely due to having an increased risk of complications. In addition to their decreased survival on the waiting list and the low likelihood of transplantation due to inequities in the lung allocation score, patients with PAH have the worst 1-year posttransplant survival.”
Poor survival shortly after transplantation may be a result of perioperative risk stemming from underlying right ventricle dysfunction and increased risk of primary graft dysfunction, noted the researchers. During transplantation, an immediate and significant reduction in pulmonary vascular resistance occurs, causing higher allograft perfusion of the right ventricle and unmasked left ventricle dysfunction. Approaches to mitigate the outcome include fluid restriction, diuretics, minimization of positive end-expiratory pressure on the ventilator, and ionotropic agents.
The presence of syncope, hyponatremia, low cardiac index, and enlarged right-to-left ventricular index have also been identified as factors contributing to poor outcomes following transplantation.
Prior to surgery, management typically focuses on ensuring the patient continues to be viable for surgery, including with use of 3-drug vasodilator therapy.
The researcher underscored the value of pulmonary rehabilitation during this period, with improvements in exercise workload and reductions in resting pulmonary pressure observed in patients with severe PAH. A recent meta-analysis of 14 randomized controlled trials showed a 48-meter improvement in 6-minute walk distance among patients who completed an exercise-based rehabilitation program.
Should a patient’s condition worsen, including experiencing full hemodynamic collapse or refractory hypoxemia, prior to transplantation, mechanical ventilation and other invasive support approaches have been used to bridge patients to transplantation.
“Severe PAH poses significant challenges at the time of induction due to the issues inherent to mechanical ventilation described above, but also because anesthetic agents can precipitate hemodynamic collapse,” explained the researchers. “Primary agents used in induction vary; however, a survey-based assessment of preferences indicated that propofol is the most common agent used in induction for lung transplantation, followed by etomidate and ketamine. Use of inhaled vasodilators such as nitric oxide and epoprostenol have potential benefit in the induction period to attenuate rises in pulmonary pressures.”
Throughout surgery, patients are monitored with an arterial line, central venous access, and transesophageal echocardiogram.
Kolaitis N. Lung transplantation for pulmonary arterial hypertension. CHEST. Published online May 5, 2023. doi:10.1016/j.chest.2023.04.047