Sex-based differences in VA-ECMO patients: gender gap or selection bias?

Abstract Background Peripheral veno-arterial extracorporeal membrane oxygenation (VA-ECMO) is used to provide cardiopulmonary support in patients with refractory cardiogenic shock or cardiac arrest. Clinical presentations of cardiogenic shock differ by gender, but whether these differences persist in patients with severe shock requiring VA-ECMO is not well stablished. Purpose To analyse gender-based differences in clinical features among peripheral VA-ECMO patients admitted to our Cardiac Intensive Care Unit (CICU). Methods We conducted a retrospective observational study of all adults who received peripheral VA-ECMO support in our CICU between January 2021 and August 2025. Data regarding baseline characteristics, procedural details and hospital course outcomes were collected. Patients were stratified by sex, and statistical comparisons were performed. Results A total of 65 patients were included: 48 males (74%) and 17 females (26%). Women were significantly younger (46.2 ±17.5 vs. 57.7 ±11.9 years; p=0.021) and had lower body weight (65.9 ±13.2 kg vs. 80.2 ±15.5 kg; p=0.003). Baseline creatinine (1 ±0.4 vs. 1.52 ±0.88 mg/dL; p=0.027) and haemoglobin (10.5 ±2.4 vs. 13.1 ±2.2 g/dL; p0.001) were also lower in women. Ischaemic cardiomyopathy was a less common aetiology in females (29.4% vs. 72.9%; p=0.002), as was VA-ECMO initiation during extracorporeal cardiopulmonary resuscitation (ECPR) (35.3% vs. 64.6%; p= 0.036). Women exhibited better PaO2/FiO2 ratio at 24h of admission (323 ±144 vs. 207 ±99; p=0.001) and lower peak C-reactive protein (11.5 ±8.8 vs. 17.9 ±12 mg/dL; p=0.036), while peak lactate levels were similar (91.9 ±65.7 vs. 81.8 ±45.3 g/dL; p=0.555). Duration of VA-ECMO support did not differ by sex (6.11 ±4.94 vs. 5.88 ±4.14; p=0.844). Mortality showed a non-significant trend toward lower rates in women (35.3% vs. 58.3%; p=0.102). In a multivariate analysis adjusted for age, sex, baseline creatinine, ECPR at admission and aetiology, only ECPR at admission was independently associated with mortality. Conclusions Female patients treated with VA-ECMO in our CICU displayed a differential clinical profile characterized by younger age, better baseline renal function and less severe initial presentation. Their lower inflammatory response and better early respiratory recovery suggest a comparatively lower-risk subgroup. These findings show a low-risk highly selected population, suggesting a potential selection bias.Clinical characteristics and outcomes Multivariate regression analysis