This retrospective propensity-matched study compared early Impella unloading (the calendar day before through the day after VA-ECMO initiation) with delayed unloading (days 2–7) in adults with cardiogenic shock, matching 282 patients per group. Thirty-day mortality was 48.9% versus 49.6% (RR 0.99, 95% CI 0.83–1.17). Early unloading was associated with more renal-replacement therapy at 30 days (37.4% versus 21.7%; RR 1.73, 95% CI 1.29–2.31), but this association disappeared with VA-ECMO-indexed follow-up in AKI-restricted cohorts. Residual confounding and immortal-time bias limit causal interpretation.
Early unloading was not associated with improved survival compared with delayed unloading. The renal-replacement therapy association was sensitive to follow-up alignment, leaving the optimal timing uncertain.
Study limitation: The retrospective design remains vulnerable to residual confounding and immortal-time bias despite propensity matching and sensitivity analyses.
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