Acute decompensated heart failure is the most common acute heart failure phenotype. Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) can provide bridging support for patients with acute decompensated heart failure to transplantation. We studied the association between baseline (<6 months), pre-ECMO (<24 h) parameters and outcome of VA-ECMO support in patients with severe acute decompensated heart failure. We included 26 consecutive patients with acute decompensated heart failure (acute myocarditis, myocardial infarction or post-cardiotomy shock were excluded) who were bridged with peripheral VA-ECMO to transplantation. Data within six months (baseline) and immediately pre-ECMO were collected. Model for end-stage liver disease (MELD) with sodium (MELD-Na) and without international normalized ratio (MELD-XI) scores were calculated. Outcome was defined as death at 30 days following VA-ECMO support. Thirteen of the 26 patients died within 30 days of VA-ECMO support. Univariate associations with 30-day mortality were baseline MELD-XI, baseline sodium, creatinine, bilirubin, pre-ECMO alanine aminotransferase and lactate. However, only baseline MELD-XI score (hazard ratio 2.678 (95% CI 1.085-6.607), p=0.033) was associated 30-day survival on logistic regression analysis. Survivors demonstrated greater reduction in inotropic and vasoactive drug support and improvement in alanine aminotransferase and lactate levels. Using a threshold based on the median MELD-XI of 14.1, 30-day survival in patients with a baseline MELD-XI ⩽ 14.1 was 69% compared with 31% in patients with baseline MELD-XI > 14.1 ( p=0.046). Baseline MELD-XI score, but not pre-ECMO parameters, is independently associated with outcomes from VA-ECMO support in patients with acute decompensated heart failure.