Prevalence of HIT among patients under VA‑ECMO is extremely low at 0.36% with an associated mortality rate of 33.3%, which appears to be in the same range as that observed in patients treated with VA‑ECMO without HIT. In addition, HIT was ultimately ruled out in one‑third of patients with clinical suspicion of HIT and positive anti‑PF4/heparin antibodies. A total of 5797 patients under VA‑ECMO were screened; 39/5797 met the inclusion criteria, with HIT con‑firmed in 21/5797 patients (0.36% [95% CI] [0.21–0.52]). Fourteen of 39 patients (35.9% [20.8–50.9]) with suspected HIT were ultimately excluded because of negative functional assays. Drug‑induced thrombocytopenia tended to be more frequent in Excluded HIT at the time of HIT suspicion (p = 0.073). The platelet course was similar between Confirmed and Excluded HIT (p = 0.65). Mortality rate was 33.3% [13.2–53.5] in Confirmed and 50% [23.8–76.2] in Excluded HIT (p = 0.48). This retrospective study included patients under VA‑ECMO from 20 French centers between 2012 and 2016. Selected patients were hospitalized for more than 3 days with high clinical suspicion of HIT and positive anti‑PF4/heparin antibodies.

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