Routine Unloading in Patients Treated With Extracorporeal Membrane Oxygenation for Cardiogenic Shock

Cardiogenic ShockMixed Outcomes Set the Stage for Future Trials Article, see p 2095 C ardiogenic shock (CS) is most commonly caused by acute myocardial infarction, accounting for 80% of cases. 1 Despite improvements in revascularization and systems of care, mortality rates are still more than 30% in contemporary studies.[2][3][4] Hence, for critically ill patients with CS who do not respond to (or who deteriorate with) initial medical therapy and supportive measures, temporary mechanical circulatory support has emerged as a promising measure to interrupt the downward spiral of hypotension and end-organ hypoperfusion that may portend cardiac death.5,6 Among the temporary mechanical circulatory support options available, venoarterial extracorporeal membrane oxygenation (VA-ECMO) provides robust biventricular and respiratory support and may be the preferred option in patients requiring cardiopulmonary resuscitation, those with poor oxygenation that is not expected to improve with other devices, and those requiring biventricular support.6 One of the recognized complications of peripheral femoral VA-ECMO cannulation is the retrograde aortic perfusion of the heart.In some patients, the resultant increase in left ventricular (LV) afterload may impair LV ejection, raise the LV end-diastolic pressure, and potentially lead to North-South (or Harlequin) syndrome wherein pulmonary edema impairs gas exchange and deoxygenated blood enters the aorta leading to further coronary or cerebral ischemia.7,8 To minimize this complication, physicians caring for patients on VA-ECMO often aim to prevent a significant rise in LV end-diastolic pressure and to maintain aortic ejection by unloading the LV, either noninvasively with inotropes or with additional mechanical circulatory support.7 Whether these strategies should be used immediately at the time of cannulation, or provisionally in patients with either rising LV end-diastolic pressures measured with pulmonary arterial catheters, or clinical evidence of pulmonary edema or impaired gas exchange remains unclear.Thus far, high-quality evidence is lacking and evidence is limited to nonrandomized studies.In a seminal 2019 meta-analysis of 17 observational VA-ECMO studies Russo et al 9 reported that LV unloading with intra-aortic balloon pump, Impella with ECMO (ie, ECMELLA), or additional transeptal left atrial drainage catheters was associated with a lower risk of all-cause mortality at the expense of higher hemolysis rates.The retrospective nature of these data, however, precluded causal inferences and could not exclude treatment and selection biases or identify provisional versus immediate unloading strategies.In addition, the sum of the ECMELLA experience was limited to only 453 patients.In this study, Schrage and colleagues performed a retrospective analysis of a 16-center international cohort of patients with cardiogenic shock (77% male, 63% acute myocardial infarction, 67% precannulation cardiac arrest, 33% cannulation during extracorporeal cardiopulmonary resuscitation) treated with ECMO. 10

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