Cardiopulmonary bypass (CPB) priming may be an important but underrecognized factor influencing outcomes after left ventricular assist device (LVAD) implantation. In this study, Bonni and colleagues examined whether blood-based CPB priming, using fresh frozen plasma (FFP) and red blood cells (RBCs), was associated with better postoperative outcomes than conventional crystalloid priming in patients receiving the HeartMate 3 (HM3) LVAD. The investigators focused particularly on right heart failure, renal dysfunction, delirium, bleeding, and survival.
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The rationale centers on hemodilution and intravascular volume management during cardiopulmonary bypass. Crystalloid solutions dilute circulating blood components and may reduce colloid oncotic pressure, potentially promoting interstitial edema and affecting organ perfusion. Blood-based priming could theoretically preserve hemoglobin concentration and oncotic pressure while reducing excessive hemodilution. These effects could be particularly important during LVAD implantation because postoperative right heart failure remains a major complication, occurring in approximately 20–40% of patients in previous studies.
The investigators conducted a retrospective, single-center observational analysis of 92 adults undergoing HeartMate 3 implantation between October 2015 and April 2025. Thirty-six patients received blood-based CPB priming consisting of four units of FFP, two units of RBCs, and heparin. Fifty-six patients received crystalloid priming consisting primarily of 1,150 mL of balanced crystalloid plus mannitol and heparin. Priming strategy was determined by surgeon preference rather than randomization. The primary endpoint was postoperative right heart failure according to INTERMACS-based criteria. Secondary outcomes included dialysis, delirium, major bleeding, transfusion requirements, and survival.
Most baseline characteristics were comparable between groups. Median age was 58 years in the blood-based group and 62 years in the crystalloid group. Measures of heart failure severity and right ventricular function were also generally similar. However, prior percutaneous coronary intervention was considerably more common among patients receiving crystalloid priming, illustrating one of the potential sources of imbalance inherent in a nonrandomized study.
Intraoperatively, cardiopulmonary bypass duration and several other treatment variables were similar. One notable finding was a higher hemoglobin concentration immediately upon intensive care unit admission among blood-primed patients: 10.3 g/dL compared with 9.2 g/dL after crystalloid priming. By 24 hours, however, hemoglobin levels were similar. This pattern supports the possibility that blood-based priming reduced the magnitude of immediate intraoperative hemodilution. Prothrombin complex concentrate use was also higher in the crystalloid group.
The most important clinical finding involved postoperative right heart failure. RHF occurred in only 3 of 36 patients receiving blood-based priming, or 8.3%, compared with 17 of 56 patients receiving crystalloid priming, or 30.4%. After adjustment for age, sex, and INTERMACS profile, blood-based priming remained associated with lower odds of right heart failure, with an adjusted odds ratio of 0.23. The authors propose that preservation of oncotic pressure and reduced interstitial fluid accumulation could potentially help protect the highly load-sensitive right ventricle after LVAD implantation.
Renal outcomes provided another potentially important signal. Dialysis was required in 11.1% of blood-primed patients compared with 32.1% of crystalloid-primed patients. After adjustment, however, the association narrowly missed conventional statistical significance, with an odds ratio of 0.30 and p=0.053. Consequently, the results suggest a possible renal benefit but cannot establish one. Better preservation of intravascular volume and renal perfusion during bypass represents one potential mechanism.
Postoperative delirium was also substantially less frequent with blood-based priming, occurring in 8.3% compared with 28.6% of patients. The adjusted odds ratio was 0.22. Delirium following cardiac surgery can arise from multiple mechanisms, including cerebral hypoperfusion, inflammation, microemboli, and metabolic disturbances. The investigators suggest that improved hemodynamic stability or microcirculatory perfusion could potentially contribute to the observed association, although the study did not include neurological monitoring or biomarkers capable of establishing such a mechanism.
Major bleeding occurred in 27.8% of blood-based patients versus 46.4% of crystalloid patients, but this difference did not reach statistical significance. Chest-drain output and postoperative transfusion requirements were also comparable. Therefore, the study does not establish that blood-based priming reduces postoperative bleeding despite the theoretical coagulation advantages of incorporating plasma into the bypass prime.
Survival similarly showed an intriguing but inconclusive pattern. With a median follow-up of 24 months, survival numerically favored blood-based priming, but the difference was not statistically significant. The Kaplan–Meier analysis reported a log-rank p-value of 0.055, while adjusted Cox regression produced a mortality hazard ratio of 0.59 with a wide 95% confidence interval of 0.27–1.32. As the authors emphasize, these data should not be interpreted as evidence that blood-based priming improves survival. The survival figure on page 23 visually demonstrates this numerical separation alongside the substantial uncertainty.
Importantly, propensity score-based inverse probability of treatment weighting was used as a sensitivity analysis. The association with delirium persisted, whereas the estimated association with right heart failure weakened and became statistically imprecise. This finding reinforces the need for caution when interpreting the primary results.
Overall, the study presents a clinically interesting hypothesis: blood-based cardiopulmonary bypass priming during HeartMate 3 LVAD implantation may reduce severe postoperative complications by limiting hemodilution and potentially improving intravascular volume preservation and end-organ perfusion. The strongest signals were lower rates of right heart failure and delirium, with a possible reduction in dialysis.
Nevertheless, the study cannot demonstrate causality. Its retrospective, single-center design, small sample of 92 patients, surgeon-selected priming strategy, potential residual confounding, and limited numbers of major events all reduce certainty. The authors appropriately characterize their results as hypothesis-generating and recommend prospective multicenter investigation, ideally through a randomized controlled trial. If subsequently validated, CPB priming strategy could represent a relatively modifiable component of LVAD surgery with meaningful implications for right ventricular and end-organ outcomes.
