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Acute Circulatory Support with ECMO: Great Achievements but Still a Long Road Ahead.

Venoarterial (VA) extracorporeal membrane oxygenation (ECMO) in the past few decades has become the mainstay of circulatory support for the treatment of refractory cardiogenic shock. There has been a resurgence of interest in ECMO with exponential increase in its use in adult population.1 Technological improvements in cannulae, membrane oxygenators, pumps, circuits, portability, and ease of deployment have undoubtedly contributed to these trends. This has made possible the movement of ECMO out of the operating rooms and intensive care units into cardiac catheterization laboratories where interventional cardiologists are becoming more comfortable in initiating ECMO support for medically unmanageable cardiogenic shock complicated by acute myocardial infarction (AMI). In the manuscript by Truby et al.,2 the authors present contemporary results of VA ECMO in 179 patients at their center supported between 2007 and 2013. Overall results in this contemporary cohort closely reflects our experience with this technology. In a diverse patient population consisting primarily of postcardiotomy shock, AMI, primary graft failure after heart transplantation, and acute decompensated heart failure, they have achieved a respectable survival to hospital discharge close to 40%. The survival data are impressive when one considers that 30% of patients were undergoing active cardiopulmonary resuscitation (CPR) at the time of initiation of treatment. This puts into perspective that without ECMO, mortality was almost certain in all these patients. More importantly the mean duration of support in survivors was 3.6 days, and close to 30% were transitioned to other shortterm device (CentriMag, Thoratec Corp., Pleasanton, CA; n = 40) or durable left ventricular assist device (LVAD; n = 10). Expeditious restoration of circulatory and pulmonary support offers the greatest advantage of ECMO and “buys” time to sort out other issues including metabolic derangements, potential for recovery, eligibility for advanced therapies such as LVAD, or decision to withdraw support because of futility of further care.3 The early determination of the prognosis of patients and the strategy to bridge select patients from ECMO to another device should be commended given the limitations and complications associated with prolonged ECMO support. Peripheral support applies constant afterload on the failing heart. In this report, 8.9% of patients developed left ventricle (LV) distention, which is likely an underestimate. Monitoring of LV distention by echocardiography is not always feasible at all times unless continuous imaging is available. Even if available, the LV geometry may not necessarily correlate with left ventricular enddiastolic pressure (LVEDP), and pulmonary complications may evolve before being clinically detectable. The use of intra-aortic balloon pump with VA ECMO was underused as the combination has a favorable effect on LV dimension and decreases pulmonary artery pressure.4 Limb ischemia (14% in this study) developed despite continuous bedside surveillance by Doppler. Again Doppler evaluation is episodic and does not adequately monitor limb perfusion particularly if patients have high pressor requirements. We favor the placement of reperfusion cannula routinely for all patients on VA ECMO with femoral arterial cannula and monitor with near-infrared spectroscopy,5 as ischemic lower extremity requiring amputation is a major impediment to long-term assist device placement. Fear of bleeding complications and unreliable monitoring of coagulation status may in itself contribute to thromboembolic complications that are not clinically detected.6 Finally, inability to ambulate the patients is a major limitation of ECMO support leading to debilitation, pulmonary complications, and prolonged hospitalization. Indeed survival results with ECMO have been remarkable, but even better success with this technology requires specialized teams dedicated to management and monitoring of patients. Continuous monitoring of LVEDP and limb perfusion, with improved anticoagulation management and early decision to transition the patients to a support system that removes leg cannulas and allows for early extubation and ambulation may lead to further improvement of results. Although challenges remain in terms of reducing the serious complications associated with ECMO such as stroke, limb ischemia, reperfusion injury, coagulopathy, and bleeding, it is still the easiest and most inexpensive form of acute circulatory and respiratory support in patients with refractory cardiogenic shock. Until more experience and data become available on other percutaneous support systems, it will remain a significant tool in rescuing otherwise dying patients. For refractory cardiogenic shock, acute circulatory support with ECMO is an immediate lifeboat with a far visible shore.