Background: The use and outcomes of pulmonary hypertension (PH) target therapy in patients with PH who undergo heart transplant (HT) is not well characterized. The objective of this study was to compare post-HT cardiac catheterization findings in patients with congenital heart disease (CHD) with and without PH.

Methods: This is a retrospective study that included all patients with a diagnosis of CHD who underwent HT at Texas Children’s Hospital from 2014-2020. Cardiac catheterization timing was divided by phases: -2 (-12 to -6 months prior to HT), -1 (-5.9 to 0 months before HT), 0 (from 2 weeks post-HT to 2 months post-HT), 1 (from 2.1-4.9 months post-HT), 2 (from 5-8.9 months post-HT), and 3 (from 9-13 months post-HT). Catheterization measurements that were assessed in the study were mean pulmonary artery pressure (mPA;mmHg), pulmonary vascular resistance (PVR;Wu.m2), transpulmonary gradient (TPG; mPA-LA pressure/wedge capillary pulmonary artery pressure [mmHg]) and pulmonary artery capillary wedge pressure (PAwp;mmHg).

Results: A total of 71 patients were included, with median age at HT of 4.3 years (IQR 0.7-11.1) and 65% were male. Race/ethnicity distribution were 54% Hispanic, 25% Non-Hispanic White, 20% Non-Hispanic Black, and 1% Asian. In this cohort, 25% of the patients underwent pre-HT placement of Ventricular Assist Device (VAD). Twenty-eight patients had pre-HT diagnosis of PH (24 single ventricle and 4 with bi-ventricular anatomy), out of which 22 were on sildenafil monotherapy, and two on dual-PH therapy. In the post-operative period, 27 patients were diagnosed with PH, out of which 20 had pre-HT PH. The median use of PH target therapy (sildenafil) after HT in the pre-HT PH group was a median of 323 days (IQR 161-584), compared to the non-PH group with a median of 116 days (IQR 46-1307), p=0.57. 
When comparing cardiac catheterization findings in patients with and without PH, there was only a difference in PVR in the post-HT period by having a decrease from 3Wu.m2 (phase -1) to 2.2Wu.m2 (Phase 0 and 1) , and 1.5Wu.m2 after phase 2 compared to the non-PH group (p=0.02, Figure 1) whose PVR remained 1.6 to 1.8Wu.m2 in the pre and post-HT period. When comparing the hemodynamic data trend in those with pre-HT PH with and without PH target therapy prior to HT, there was no difference in mPA pressure (p=0.09), PVR (0.2), or TPG (0.09), Figure 2. However, when comparing cardiac catheterization data in the post-HT period in patients with uni or biventricular anatomy, those with univentricular anatomy had a significant PVR downtrend characterized by median PVR of 2.9Wu.m2 (phase -1) to 1.9 Wu.m2 (phase 0) and 1.5 Wu.m2 (phase 3), p<0.001; but there was no trend difference in mPA (p=0.94), or TPG (p=0.87) when comparing both groups, Figure 3. 

Conclusion: Pediatric patients with congenital heart disease and pulmonary hypertension who undergo HT, particularly those with single ventricle physiology and/or receiving medical therapy for PH, have a significant improvement in PVR post-HT. This may potentially indicate the ability to wean off pulmonary vasoactive medication at an earlier interval.