Successful Single Lung Transplantation in Severe Group III Pulmonary Hypertension

Abstract

Lung transplant provides a durable long-term option for group III pulmonary hypertension patients. Historically, bilateral lung transplant is the preferred option due to superior long-term survival. This benefit manifests itself after 2 years posttransplantation. Recipient medical urgency and organ availability may blunt the benefits of bilateral lung transplant over single lung transplant, necessitating alternative transplant strategies. We report a patient with group III pulmonary hypertension with clinical deterioration while awaiting double lungs who underwent salvage single lung transplant. The patient demonstrated excellent graft function with pulmonary hypertension resolution, highlighting the beneficial potential role of single lung transplant in this patient group.

Patients who develop secondary pulmonary hypertension in the setting of progressive chronic lung disease have been shown to have poor long-term outcomes with increased mortality.¹ Medical therapies for pulmonary hypertension (PH) exist for slowing disease progression and alleviating symptoms. Lung transplantation remains the most effective and durable option for patients who fail medical treatment modalities.

There is a growing trend toward bilateral lung transplant (BLT) for surgical management of end-stage lung disease, mainly due to the improved long-term survival associated with BLT compared with single lung transplant (SLT).2, 3, 4 These differences manifest beyond 2 years posttransplant. While long-term survival is an essential factor, it is only one of many elements that need to be considered before transplantation. With increasing numbers of patients eligible for transplants each year, the demand for organs has never been higher.⁴ The introduction of the continuous allocation system has provided a decrease in overall waitlist mortality rates, yet patients with prolonged wait times still endure risk for adverse events. There is conflicting literature regarding short-term posttransplant outcomes, with some suggestions of improved early survival after SLT.^5,6 BLT carries higher perioperative risk, has increased technical complexity, longer operative times, higher bleeding risk and transfusion requirements, and increased potential for airway complications.⁷

While the preferred surgical option for patients with PH is BLT, cautious application of SLT has been shown to be successful.⁸ The decision for the optimal procedure is complex and should be individualized based on recipient and donor characteristics. We present a case demonstrating the effective utilization of SLT in the management of a patient with progressively worsening PH and clinical deterioration while awaiting BLT.

Our patient is a 59-year-old male individual initially admitted for severe acute COVID-19 pneumonia with prolonged and complex hospital course, requiring mechanical ventilation with a tracheostomy and extracorporeal membrane oxygenation support. After a stay of over 100 days, he ultimately recovered sufficiently to be discharged home with supplemental oxygen. Several months later, he was hospitalized with acute exacerbation and diagnosed with post-COVID pulmonary fibrosis. Workup included right heart catheterization, revealing severe pulmonary hypertension with systolic/diastolic/mean pulmonary artery (PA) pressures of 70/30/49 mm Hg. He was discharged home on increased oxygen support, inhaled prostacyclin vasodilator, and pulmonary rehabilitation.

Despite optimal medical management, he continued to show disease progression, with right heart dysfunction. Echocardiogram findings included tricuspid regurgitation, and persistent elevated right heart pressures. Chest radiograph showed diffuse severe bilateral reticular opacities. On computed tomography scan of the chest, there was evidence of severe diffuse interstitial lung disease with ground glass and reticular opacities with bilateral lower lobe predominance (Figure 1). Perfusion scan showed 57% perfusion to the right lung and 43% to the left lung. On 6-minute walk, he was only able to ambulate 450 feet while requiring 15 L oxygen. Given his respiratory decline and persistent pulmonary hypertension, he was brought to the multidisciplinary lung transplant selection committee. He was approved for BLT listing with lung allocation score of 53 and blood type B.

Figure 1.

Chest computed tomography (CT) and chest radiograph (CXR) during evaluation and comparison. (L, left.)

After 6 months on the waitlist, his disease continued to progress, yet organ offers for transplant were limited and not suitable. Speculatively, at 5′4”, his relatively short stature may have contributed to his limited donor offers as he was competing with pediatric cohorts. Being blood type B likely also limited his options given the relative rarity of this blood type. He did not have elevated human leukocyte antigen antibodies. In the interim, his oxygen requirement continued to rise and his ability to take care of himself became severely limited. His echocardiogram showed persistent severe pulmonary hypertension with worsening tricuspid regurgitation, despite a structurally normal valve, and a dilated pulmonary artery. There was continued evidence of right heart dysfunction with paradoxical interventricular septal motion “D-sign” indicative of elevated right heart pressures (Figure 2). To expand his donor pool, extended criteria were applied, including organ preference to single or double lung, enlarged travel radius, and increased donor height range. Within a short interval, a viable organ became available with predicted total lung capacity ratio of 1 indicating ideal size matching, and he underwent a right SLT.

Figure 2.

Echocardiographic changes posttransplant compared with pretransplant. (A) Parasternal short axis view depicting elevated right heart pressures with dilated RV with abnormal septal bowing forming the “D-sign” of the LV pretransplant. (B) Parasternal short axis showing restoration of normal biventricular function posttransplant. (C) Apical 4-chamber view showing enlarged RA and RV pretransplant. (D) Apical 4-chamber view with normal anatomy posttransplant. (LA, left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle.)

In the operating room, his PA pressures were 82/57/65 mm Hg upon induction of anesthesia. Intraoperative transesophageal echocardiogram confirmed a dilated tricuspid annulus, moderate to severe regurgitation, with no leaflet abnormalities. Due to clinical evidence of right heart dysfunction, we elected to perform the transplant with the use of intraoperative extracorporeal membrane oxygenation support accomplished via bilateral femoral cannulation. After implantation and controlled reperfusion, he was successfully weaned from extracorporeal membrane oxygenation support. Total intraoperative support time was 70 minutes. At the completion of the procedure, PA pressure decreased to 51/20/31 mm Hg. Completion transesophageal echocardiography showed improved tricuspid leaflet coaptation, improved right heart strain, and only mild tricuspid insufficiency. Postoperatively, his course was complicated by grade 3 primary graft dysfunction and he was extubated on day 6. He recovered with supportive care and demonstrated improvement in right heart hemodynamics. On postoperative day 7, PA pressures decreased to 37/13/21 mm Hg with improved tricuspid regurgitation and normalization of right heart function on echocardiogram.

His allograft continues to thrive on longitudinal posttransplant follow-up without development of chronic lung allograft dysfunction. His hemodynamics remain stable with only mild tricuspid regurgitation and normal right heart function with no evidence of pulmonary hypertension. Almost3 years after SLT, the patient remains well, able to self-care, and achieves 1200 feet ambulation on room air on 6-minute walk. He continues to have stable pulmonary function, presently his forced expiratory volume in 1 second is 1.46 L (54% predicted) compared with his peak forced expiratory volume in 1 second over the course of follow-up of 1.62 L or 62% predicted (Figure 3).

Figure 3.

Pulmonary function trend. (FEV1, forced expiratory volume in 1 second; SLT, single lung transplant.)

Comment

The decision between BLT and SLT should be patient-specific, accounting for multiple considerations. It is important to recognize the decision for transplantation and choice of allograft preference remains very nuanced. Waitlist time is a notable factor. Our patient was listed in a marginalized donor pool due to his height and blood type, this likely resulted in his prolonged wait time. His clinical course was becoming tenuous with progressive respiratory disease and worsening pulmonary hypertension while he was awaiting double lungs. The increased medical urgency for transplantation dictated expanded allograft preferences. Expanded travel radius would have increased ischemic time. Increased donor height could have resulted in size mismatch, for larger lungs may require wedge resections for our patient’s chest to accommodate the graft. These concessions would have been acceptable given the imminent need for an organ, as his clinical status was becoming increasingly difficult to manage. In this case, SLT not only allowed him to return to baseline activity levels but also remediated his pulmonary hypertension and right heart dysfunction. While the long-term survival data may support the use of BLT over SLT, especially in the group III PH patient population, it is not the only factor that should be considered. Prudent decision-making for extended criteria proved to be lifesaving in this case and prevented waitlist mortality.