Improvement in pulmonary vascular resistance with IMPELLA 5.5 as a bridge to orthotopic heart transplantation

Purpose The Impella 5.5 is a temporary micro-axial mechanical circulatory support (tMCS) device used for left ventricular (LV) support and unloading as a bridge to advanced therapies. However, the short-term impact of LV unloading on pulmonary hypertension (PH) has not been clearly defined. This study explored whether Impella 5.5 support results in a reduction in PH in patients bridged to orthotopic heart transplantation (OHT). Methods This retrospective observational study examined 75 patients from two tertiary cardiac centers who had an Impella 5.5 placed during an admission (2018–2025) that culminated in OHT. Right heart catheterization (RHC) and transthoracic echocardiography (TTE) data were collected, including studies obtained before and after Impella placement. The primary outcomes were changes in pulmonary vascular resistance (PVR), mean pulmonary artery pressure (mPAP), and pulmonary artery systolic pressure (PASP). Secondary outcomes included changes in qualitative right ventricular (RV) systolic function, transpulmonary gradient (TPG), and pulmonary artery pulsatility index (PAPi). Paired and unpaired analyses were conducted. For the primary unpaired analysis, differences between the pre-Impella and during-Impella time points were assessed using the Wilcoxon rank-sum test for continuous variables and chi-square or Fisher's exact test for categorical variables. Results Following Impella 5.5 placement, median PVR by Fick and Thermodilution decreased from 2.8 (IQR, 2.1–3.8) to 1.5 (1.2–2.1) Wood Units (WU) ( p < 0.001) and from 2.4 (1.9–2.8) to 1.3 (1.0–1.5) WU ( p < 0.001), respectively. Median mPAP and PASP decreased from 35.5 (31.0–41.8) to 24.5 (20.2–32.0) mmHg ( p < 0.001) and from 48 (42.0–55.8) to 37.5 (27.5–42.0) mmHg ( p < 0.001), respectively. Secondary outcomes showed an increase in PAPi from 1.9 (1.3–3.0) to 3.4 (2.0–5.6; p = 0.002). The median duration of Impella 5.5 support was 19.0 (10.0–31.0) days, and the median time from Impella to RHC was 14 (12.0–17.0) days. Conclusion Temporary mechanical circulatory support with the Impella 5.5 device led to rapid and significant reduction in PVR, mPAP and PASP in patients being bridged to OHT. These findings support the use of the Impella 5.5 for optimizing pre-transplant hemodynamics and suggest a potential role for tMCS in improving transplant candidacy among patients previously excluded due to PH.