PM1029: Pulmonary Artery Size as a Predictor of Early Post-operative Heart Transplant Outcomes

Background: Pulmonary artery (PA) size has been studied as a predictor of outcome after congenital heart disease (CHD) surgery. There are limited data evaluating PA size as a predictor of outcome after pediatric and congenital orthotopic heart transplant (OHT) patients. The objective of this study was to evaluate pre-operative PA size as a predictor of early post-transplant outcomes.

Methods: Data were collected retrospectively from patients undergoing OHT at our center from 2014-2021. Baseline variables included demographics, cardiac diagnosis, and need for PA reconstruction during OHT. Echocardiography (n=40), CT (n=26) and cath angiography (n=17) were used to measure proximal left and right PA size; PA lower lobe measurements were also made from the latter two modalities. PA size cross-sectional areas were calculated, indexed to body surface area, and the Nakata index (NI, mm2/m2) was calculated. Outcomes included length of stay (LOS), post-OHT cardiovascular function (assessed by echocardiography, CVP, inotrope scores), end-organ function, and 2-year mortality. Statistical analyses included Pearson and Spearman rank correlations, chi-squared tests, and Mann Whitney U tests.

Results: Included were 40 patients; median age at OHT 7.7 years (IQR 1.7-15.8) with 53% (n=21) having a primary diagnosis of CHD. Indexed proximal and lower lobe PA size and NI were generally not associated with outcomes, including cardiovascular function, end-organ function, ICU or hospital LOS, or mortality. However, lower NI by echocardiography was associated with PA reconstruction (p=0.002) and trended toward correlation with peak post-OHT bilirubin (r=0.31; p=0.053). CHD patients trended toward lower echocardiography NI (138 vs 195 mm2/m2) but did not reach significance (p=0.145). Primary CHD diagnosis was associated with mortality (n=6, p =0.011), PA reconstruction (p < 0.001), post-OHT dialysis (p=0.011) and peak bilirubin (p < 0.001). PA reconstruction during OHT was performed in 14 patients (35%), all with CHD. Patients undergoing PA reconstruction had lower echocardiography NI (median 135 vs 204 mm2/m2; p = 0.002), were more likely to require post-OHT dialysis (p=0.014), had higher post-OHT peak bilirubin (p < 0.001) and higher mortality (p=0.014).

Conclusion: PA size as measured by CT and cath angiography was not predictive of outcome. However, in a larger sample, proximal PA size by echocardiography measured NI was associated with PA reconstruction and higher post-OHT bilirubin. Importantly, we identified additional risk factors for mortality and post-OHT hepatic and renal insufficiency, including the presence of CHD and need for PA reconstruction. We acknowledge the limitations of our small sample size and using NI as a measurement of pulmonary vascular bed adequacy. Future directions include evaluating related risk factors including pulmonary artery hemodynamics and other pre-operative and intra-operative risk factors for OHT as we expand our patient population.