16
The largest published series. It establishes that most episodes resolve without reconfiguration and that they resolve quickly - a median of 4.5 hours - which supports treating the lung first and reserving circuit revision. It cannot establish that any particular intervention caused resolution, nor whether earlier revision would have helped those who deteriorated.
No revision - physiological interventions only, 33 patients (75%)
DOI 10.1007/s12055-026-02185-w
ECMO revision (circuit reconfiguration), 11 patients (25%)
Retrospective, single centre, no control group and no adjustment. The two groups are not comparable - the SAVE difference shows revision was chosen for much sicker patients, which makes the near-identical survival uninterpretable in either direction. The article as retrieved does not state the diagnostic criteria used, the denominator, or which specific interventions were applied to how many patients.
Median time to resolution of Harlequin syndrome for the whole cohort 4.5 hours (IQR 1.4 to 7.80). Survival to decannulation 8 of 11 (73%) in the revision group versus 23 of 33 (70%) in the non-revision group. Hospital length of stay similar. Baseline severity was markedly different: SAVE score -15 (IQR -17 to -11) in the revision group versus -6.0 (IQR -10 to -1) in the non-revision group. Authors conclude that physiological interventions can effectively resolve Harlequin syndrome and should be considered as a key strategy before ECMO revision.
44 patients who developed Harlequin syndrome on femoral VA ECMO at a single institution, March 2016 to May 2021. Indian Journal of Thoracic and Cardiovascular Surgery 2026;42(8):935-942. Retrieved in full. The denominator of VA ECMO patients over the period is NOT stated, so no incidence can be derived.