The impact of blood type and body size on successful bridging to heart transplantation using intra-aortic balloon pump or surgically implanted microaxial left ventricular assist device.

Objective: Waitlist time for United Network for Organ Sharing Status 2 heart transplant candidates has steadily increased. We compared a bridging strategy using either the Impella 5.0/5.5 ("Impella") or intra-aortic balloon pump with a durable left ventricular assist device in patients with blood type O stratified by body habitus.

Methods: The United Network for Organ Sharing registry was queried for adults listed for de novo heart transplantation (without dialysis) supported by the Impella, an intra-aortic balloon pump, or the HeartMate 3 left ventricular assist device. The primary outcome was 1-year postlisting survival, defined as the sum of waitlist time and post-heart transplant survival time if the candidate underwent heart transplantation.

Results: In total, 2942 candidates were included (Impella: 214; intra-aortic balloon pump: 1326; HeartMate 3: 1402). Listing with the Impella or intra-aortic balloon pump was associated with worse postlisting survival compared with the HeartMate 3 left ventricular assist device in type O candidates (Impella: hazard ratio, 2.90 [95% CI, 1.48-5.67], P = .002; intra-aortic balloon pump: hazard ratio, 2.42 [95% CI, 1.59-3.68], P < .001) but less so in non-type O candidates. Further analysis of type O candidates demonstrated that the Impella and intra-aortic balloon pump were associated with a lower risk of postlisting mortality among those with normal height (25-75th percentile) and nonobese (body mass index <30) (Impella: hazard ratio, 1.78 [95% CI, 0.61-5.18], P = .292; intra-aortic balloon pump: hazard ratio, 1.28 [95% CI, 0.67-2.45], P = .455); among those not of normal height and nonobese, the Impella and intra-aortic balloon pump were associated with an elevated risk of postlisting mortality (Impella: hazard ratio, 3.65 [95% CI, 1.68-7.95], P = .001; intra-aortic balloon pump: hazard ratio, 3.01 [95% CI, 1.95-4.67], P < .001).

Conclusions: Blood type O candidates listed with the Impella or intra-aortic balloon pump are at increased risk of postlisting mortality compared with a durable left ventricular assist device in the current organ allocation era. These effects are diminished among those with normal height and body habitus.