3 DISCUSSION
The argument for heart-lung transplantation for patients with pulmonary
arterial hypertension (with or without a giant PAA) is no longer
compelling with the knowledge that even the most adversely remodeled
right ventricle, such as those preoperatively requiring inotropic or VA
ECMO support, will reverse remodel after lung transplantation alone
[9]. Most centers try to avoid heart-lung transplantation when
possible, due to the shortage of donor organs as well. In the most
recent analysis of the International Society of Heart Lung
Transplantation (ISHLT) registry the 1,3 and 5 year survival in
heart-lung transplantation for PAH was 87.3%, 68.6 and 61.8
respectively. In comparison the 1,3 and 5 year survival for all lung
transplant recipients for PAH transplanted between 2008 and 2015 were
80.7%, 63.4% and 55.2% respectively [10]. Consequently, the
decision for heart-lung transplant in PAH is reserved for patients with
severe left ventricular failure or those with anticipated difficulty in
repairing complex congenital heart disease [11-13]. Case 2 required
heart-lung transplantation due to the underlying complex congenital
heart disease and severe PH with PAA.
In PAH patients the prostacyclin analogue intravenous epoprostenol has
been found to significantly increase transplant free survival [10, 14,
15]. Intravenous epoprostenol is reserved for patients with WHO class
IV symptoms, where it is used in combination with one or both of an
endothelin receptor antagonist and a phospho-di-esterase 5 inhibitor
[16, 17]. In addition to initiating epoprostenol therapy, early
referral of patients with WHO class III or IV symptoms to a transplant
center is appropriate given their higher rate of disease progression and
mortality [16].
However, with PAA in the setting of PAH, an increase in size is
independent of normalized pressures [18], and progression of
dilation and chest pain are indications for urgent transplant due to the
risk of dissection and rupture. The rare complication of PAA poses
substantial problems for lung transplantation and traditionally,
combined heart-lung transplantation has been recommended as the
treatment of choice. Sole lung transplantation is being increasingly
recognized as an alternative in experienced lung transplant centers. In
a relatively large 12-year series, Schwarz et al. reported 7 of 127
patients with PAH presented with severe PAA in their 12 year series.
Their institutional experience with a lung-only strategy, where donor PA
trunk was procured along with the lungs, and the main PA was
reconstructed along with the implantation of the right lung. The left
lung was then implanted and the left PA was reconnected to the main PA.
Their series demonstrates feasibility of this approach in this complex
group of patients [19]. Shayan et al. reported a case where the
donor pulmonary trunk was procured with the lungs [20]. They
implanted the lung allograft bloc by positioning it posterior to the
heart and anastomosing the trachea instead of separate bronchial
anastomoses. Force et al. and Noda et al. described techniques where
donor thoracic aorta was fashioned to replace the recipient PAA which we
employed in Case 1. It is important to carefully assess the pulmonary
arterial and right ventricular pressures following replacement of the
pulmonary arteries, especially in cases where extensive reconstruction
was required.