C52-06 Harlequin Syndrome in a Patient Undergoing Veno-Arterial Extracorporeal Membrane Oxygenation Successfully Treated With Veno-Arteriovenous Extracorporeal Membrane Oxygenation

Introduction Harlequin syndrome is a rare but potentially life-threatening complication of veno-arterial extracorporeal membrane oxygenation (VA-ECMO) characterized by poorly oxygenated blood in the upper body and adequately oxygenated blood in the lower body. This oxygenation differential requires prompt recognition and management to mitigate cerebral hypoxia. We report a case of Harlequin syndrome following VA-ECMO initiation in a patient with refractory cardiogenic shock secondary to a non-ST-elevation myocardial infarction, which resolved with conversion to veno-arteriovenous ECMO (VAV-ECMO). Case Description A 40-year-old man with a history of hypertension, dyslipidemia, and obstructive sleep presented to the emergency department with chest pain radiating down the left arm. Electrocardiography revealed ST-segment depressions in the lateral and septal leads, and an initial high-sensitivity troponin I of 351 ng/L. The patient was taken for left cardiac catheterization; however, prior to the procedure, he experienced a ventricular fibrillation arrest. After return of spontaneous circulation, the patient was in refractory cardiogenic shock despite vasoactive infusions, requiring initiation of VA-ECMO via femoral cannulation. Subsequent coronary angiography revealed distal left circumflex disease that was successfully treated with one drug-eluting stent. In the intensive care unit, an arterial blood gas from the right radial artery demonstrated severe hypoxemia that was discordant from blood obtained via the ECMO circuit. The ECMO configuration was subsequently converted to VAV-ECMO with venous return via the right internal jugular vein, resulting in normalization of arterial gases and resolution of the differential hypoxemia. The patient was subsequently transferred to a tertiary care center, where he underwent atrial septostomy and was weaned off ECMO. Discussion This case emphasizes the need for prompt early recognition of Harlequin syndrome in patients on VA-ECMO. The condition, also known as North-South syndrome or differential hypoxemia, arises when poorly oxygenated blood from the recovering left ventricle perfuses the upper body, while the lower body receives well-oxygenated blood from the ECMO pump. This syndrome typically arises in the setting of femoral cannulation and partial cardiac recovery. Recognition depends on identifying differences in upper- and lower-body oxygenation via continuous saturation monitoring or arterial blood gases. Prompt management is essential to prevent cerebral or myocardial hypoxia. Strategies include optimizing ventilation, adjusting ECMO flow, providing additional temporary mechanical circulatory support (i.e., Impella), or converting to VAV-ECMO, the latter of which effectively restored upper body oxygenation in this case.