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Percutaneous Extracorporeal Membrane Oxygenation: The Newest Iteration of Temporary Mechanical Support for the Left Ventricle
The ability to effectively support the left ventricle is a central component of the care of patients with life-threatening cardiovascular diseases, including cardiogenic shock (CS) and cardiac arrest (CA). As initially described by Hollenberg in 2001, patients with CS progress through a rapid, downward cascade of hypotension, hypoxemia, reduced coronary artery perfusion, and ischemia (Figure 1).1 The ability to halt and/or reverse progressive myocardial dysfunction and this “downward spiral” with a mechanical support device is paramount to survival. The intraaortic balloon pump (IABP) is the most commonly used device for this indication because of ease and speed of insertion, widespread availability, and low cost. However, recent randomized clinical trials have questioned whether routine use of the IABP in the setting of CS improves clinical outcome.2 In addition, the IABP only increases cardiac output by up to 1.0 L/minute. Because of these limitations, several newer forms of mechanical support have emerged into clinical practice. Each device has advantages and disadvantages as summarized in Table 1. Similar to patients with CS, those with in-hospital CA also have a poor prognosis.3 A recent study from Taiwan suggests a benefit in neurologic outcome and survival for patients receiving extracorporeal membrane oxygenation (ECMO) vs conventional cardiopulmonary resuscitation.4 In addition to temporarily supporting the left ventricle with a mechanical device, correcting the underlying cause(s) that lead to the arrest and/or left ventricle failure is crucial. Timely primary percutaneous coronary intervention, rapid correction of electrolyte and acid-base abnormalities, optimization of volume status, and restoration of flow to an occluded proximal pulmonary artery in the setting of massive pulmonary embolism are several examples.
Traditional ECMO systems required placement of large-bore arterial and venous cannulas within the operating room by vascular and/or cardiothoracic surgeons and trained perfusionists to run the circuits. However, newer miniaturized ECMO systems can now be placed either at the bedside or in the cardiac catheterization laboratory using traditional percutaneous techniques. The CardioHelp system (Maquet Cardiovascular) represents the newest iteration in peripheral ECMO as a miniaturized, single hybrid pump-oxygenator unit that weighs 9 kg and was initially developed as a compact system for helicopter transport in communities without nearby tertiary-care facilities. The system can achieve cardiac outputs of 5.0 L/minute, with higher flow rates possible using larger-diameter venous and arterial cannulas. The system is relatively easy to initiate with percutaneous arterial and venous access and also allows oxygenation of venous blood for patients with coexisting hypoxia.
In this issue of the Journal of Invasive Cardiology, Czobor et al describe a contemporary series of 25 patients who received the CardioHelp system for CS and CA.5 The authors applied the Sequential Organ Failure Assessment (SOFA) score to quantify the severity of organ failure prior to placement of the CardioHelp system.6 In addition, they evaluated the association of arterial cannula size on clinical outcome and bleeding complications. Thirty-day survival was associated with a lower SOFA score at presentation and smaller arterial cannula size. The authors propose that smaller cannula size may be associated with fewer bleeding complications and therefore improved survival. Additional questions raised the Czobor et al study include a better understanding of methods to further reduce vascular and bleeding complications. Use of antegrade superficial femoral artery puncture with a 4 or 5 Fr sheath is a commonly used method to improve distal blood flow. The double-Perclose (“preclose”) technique at the time of initial arterial access and the use of ultrasound and/or fluoroscopy may also reduce vascular and bleeding complications. Although the authors used body mass index to estimate the appropriate arterial cannula size, additional factors may be related to the required amount of device flow. These include pump speed, volume status, severity of left ventricular (and right ventricular) dysfunction, duration of illness, and underlying acid-base status. A more complete understanding of all these related factors may allow better precision when choosing cannula size. From the description of the patient cohort, it is not clear which patients had potentially treatable underlying illnesses such as an acute coronary syndrome and massive pulmonary embolism. In the setting of a treatable condition, prognosis would be expected to be improved. An additional practical issue when using percutaneous ECMO is determining the optimal duration for device support. The authors state that weaning was started from full flow to approximately 1 L/minute while observing hemodynamic status. It would be important to understand at which time frame this occurred; this would, perhaps, reduce the ongoing risk of bleeding and vascular complications during device use.
To date, there are relatively few additional publications describing clinical use of the CardioHelp system.7-11 One of the initial publications describing use of mini-ECMO systems is from Arlt et al from Germany.9 In this series of 21 patients with CS, the first-generation mini-ECMO device and the CardioHelp device were placed and patients were then transferred by helicopter to a tertiary-care center for definite treatment. ECMO devices were placed percutaneously at the referring facility by the ECMO team, which included a cardiac anesthesiologist, a cardiac surgeon, a perfusionist, and a nurse. In current clinical practice, a perfusionist, cardiac surgeon, and cardiac anesthesiologist are no longer required. Thirteen of 21 patients (62%) survived to hospital discharge. Survivors tended to be younger, have a lower SOFA score (median, 9.7), and higher pH prior to ECMO initiation.
The studies by Arlt et al and Czobor et al both suggest that physicians should consider use of objective scoring systems, such as the SOFA score, when evaluating patients for advanced device support. The ability to accurately identify patients who will derive benefit from temporary left ventricular support and, equally important, the ability to identify patients who are too critically ill for whom use of temporary left ventricular support is futile, remain challenging. Use of objective scoring systems, additional operator experience with newer devices, and additional clinical trials and registries will hopefully provide this information.
References
1. Hollenberg SM. Cardiogenic shock. Crit Care Clin. 2001;17:391-410.
2. Thiele H, Zeymer U, Neumann FJ, et al; IABP-SHOCK II Trial Investigators. Intraaortic balloon support for myocardial infarction with cardiogenic shock. N Engl J Med. 2012;367:1287-1296.
3. Cooper S, Janghorbani M, Cooper G. A decade of in-hospital resuscitation: outcomes and prediction of survival? Resuscitation. 2006;68:231-237.
4. Chen YS, Lin JW, Yu HY, et al. Cardiopulmonary resuscitation with assisted extracorporeal life-support versus conventional cardiopulmonary resuscitation in adults with in-hospital cardiac arrest: an observational study and propensity analysis. Lancet. 2008;372:554-561.
5. Czobor P, Venturinia JM, et al. Sequential organ failure assessment score at presentation predicts survival in patients treated with percutaneous veno-arterial extracorporeal membrane J Invasive Cardiol. 2016;28:133-138. Epub 2016 Feb 15.
6. Vincent JL, Moreno R, Takala J, et al. The SOFA (Sepsis-related Organ Failure Assessment) score to describe organ dysfunction/failure. On behalf of the Working Group on Sepsis-Related Problems of the European Society of Intensive Care Medicine. Intensive Care Med. 1996;22:707-710.
7. Philipp A, Arlt M, Amann M, et al. First experience with the ultra compact mobile extracorporeal membrane oxygenation system Cardiohelp in interhospital transport. Interact Cardiovasc Thorac Surg. 2011;12:978-981.
8. Haneya A, Philipp A, Foltan M, et al. First experience with the new portable extracorporeal membrane oxygenation system Cardiohelp for severe respiratory failure in adults. Perfusion. 2012;27:150-155.
9. Arlt M, Philipp A, Voelkel S, et al. Hand-held minimised extracorporeal membrane oxygenation: a new bridge to recovery in patients with out-of-centre cardiogenic shock. Eur J Cardiothorac Surg. 2011;40:689-694.
10. Alwardt CM, Wilson DS, Alore ML, Lanza LA, Devaleria PA, Pajaro OE. Performance and safety of an integrated portable extracorporeal life support system for adults. J Extra Corpor Technol. 2015;47:38-43.
11. Roncon-Albuquerque R Jr, Basílio C, Figueiredo P, et al. Portable miniaturized extracorporeal membrane oxygenation systems for H1N1-related severe acute respiratory distress syndrome: a case series. J Crit Care. 2012 Oct;27:454-463.
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From the Division of Cardiovascular Medicine, University of Southern California, Los Angeles, California.
Disclosures: The author has completed and returned the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Shavelle has served as a paid consultant to St. Jude Medical and receives research support from St. Jude Medical, Abbott Vascular, AbioMed, and the National Institutes of Health.
Address for correspondence: David M. Shavelle, MD, FACC, FSCAI, Division of Cardiovascular Medicine, Keck School of Medicine, 1510 San Pablo Street, Suite 322, Los Angeles, CA 90033. Email: shavelle@med.usc.edu
