Complex decisions in RV recovery: lung or heart-lung transplant

Dr. Philip Camp opened the second day’s lecture series with a review of the epidemiology, indications, eligibility, and outcomes for patients undergoing heart-lung transplantation, as compared to lung transplantation alone. Considerable advances in medical therapy and the ability to follow patients over time have contributed to a decrease in the acute need for heart-lung en bloc transplantation. According to the International Society for Heart and Lung Transplantation (ISHLT) registry, the number of heart-lung transplants has indeed declined from 1990 to 2010, with less than a third of these being performed for idiopathic pulmonary arterial hypertension (IPAH).^1,2 Selection criteria for lung and heart-lung transplant were reviewed, and it was emphasized that appropriate patient identification and transplant discussion must occur early in the treatment process. Eligibility entails the absence of significant multisystem dysfunction, New York Heart Association class III or IV functional status, and failure of medical therapies.

Candidacy for lung transplantation alone in the United States is determined by a scoring system known as the lung allocation score, with groups A–D used to categorize patients according to underlying pathology. Overall median wait time for lung transplantation is now 3.6 months. Patients with PVD (group B) experience the longest wait times, at a median of 9.7 months, compared to the 2.1-month median wait time for patients with restrictive lung disease patients (group D).³

Which transplant is the optimal choice? Single-lung transplantation for pulmonary hypertension (PH) has largely been abandoned because of adverse postoperative outcomes, including pulmonary edema, graft dysfunction, and need for prolonged mechanical circulatory support (MCS) and ventilation.^1,2 The gold-standard and most common surgical treatment option is double lung transplantation, which allows for lower rates of postoperative diffuse alveolar damage, delayed onset of bronchiolitis obliterans syndrome (which may play a role in chronic rejection), improved pulmonary vascular resistance (PVR), and sustained improvement in RV ejection fraction (EF).^4,5 Despite these noted advances, survival for PH patients after transplant remains suboptimal, with a median survival of 5 years. The early postoperative period (3–6 months) remains the time of greatest vulnerability for IPAH patients; however, if survival is maintained beyond years 1–3, long-term outcomes are superior to those for patients with chronic obstructive pulmonary disease (COPD), sarcoidosis, or idiopathic pulmonary fibrosis (IPF) (Fig. 1).^1,2

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Heart-lung transplantation remedies the scenario in which a patient is deemed “too sick” for lung transplantation alone for fear of unrecoverable right ventricle (RV) function. Though historic indications of congenital heart disease and PH with poor RV function remain relevant, contemporary candidates include patients inappropriate for MCS bridging or who have suffered MCS-related complications. The large dual-organ bloc is implanted with a short ischemic time and naturally provides a matched cardiopulmonary relationship. Wait times are increased, and long-term survival is reportedly lower (64% at 1 year),^1,2 compared to those for lung transplant alone. These data are not randomized, however, and may be a reflection of pretransplant heart-lung patients being more critically ill, with worse end-organ damage. Survival for PAH patients undergoing heart-lung transplant is similar to patients with congenital heart disease.¹

Despite increases in lung transplantation worldwide, only a minority of these procedures are performed for PH and RHF. Determining the optimal timing of transplantation for these patients remains challenging. Eligibility often follows only when right atrial pressures exceed 15 mmHg and/or when the cardiac index is measured as less than 1.8 L/min/m² and patients are in cardiogenic shock, which obviates MCS as a bridge to transplant and may increase chances of adverse events after transplantation. Although posttransplant survival has improved for PH patients, the current allocation scoring system may place them at a disadvantage relative to other groups on the pretransplant wait list.⁶ Recent attention to this matter prompted a reevaluation of predictors of mortality and wait times and may lead to the incorporation of other factors that reflect heart failure.⁷ Dr. Camp concluded his presentation with a proposed shift in the PH-RV treatment paradigm from “treating the failing organ to rescuing and resuscitating the failing organ,” invoking reports of MCS used to salvage the RV and lungs.⁸ With extracorporeal life support, for example, the RV may be allowed a chance to positively remodel, which could lead to improved outcomes after transplant.