Cardiogenic shock, an outcome of various cardiac diseases, results in cardiac pump failure, which leads to significant “supply-demand” mismatch and causes decreased tissue perfusion. Due to the complicated and heterogenic nature of cardiogenic shock, it has been one of the most challenging conditions to manage, and resulting mortality still remains high at 50-60%.¹ Despite the underlying etiology, pharmacologic approaches (including inotropes and vasopressors) have been the mainstay of therapy to stabilize the patient, while a definitive therapy (such as reperfusion therapy in acute coronary syndromes [ACS] patients) is instituted. Although the most common management strategy is initiating inotropes with the addition of vasopressors when hypotension persists, the efficacy of this approach has never been tested in a prospective controlled trial. During the last 10 to 15 years, there has notably been very limited progress in pharmacological therapies for cardiogenic shock.² With the recent advances in mechanical circulatory support (MCS) options, this strategy is increasingly being used as a “bridge-to-MCS” rather than a “bridge-to-recovery” approach.

When the patient continues to exhibit poor organ perfusion despite the conventional pharmacological therapy, cardiogenic shock is defined as “refractory” with a very poor prognosis.³ It seems that the timely institution of MCS can significantly improve outcomes.³ However, the availability of appropriate forms of MCS could be a challenging issue for many centers. MCS is still mostly limited to tertiary centers, and transferring a hemodynamically unstable patient with cardiogenic shock to another hospital can be problematic. A potential solution is to mobilize a team of MCS specialists from an experienced center, send them to a referring hospital, stabilize the patient with temporary MCS, and safely transfer the patient to the referred hospital. Leprince et al. recently published their experience with this strategy. The authors launched a program utilizing a Mobile Unit of Cardiac Assistance (MUCA) to offer extracorporeal membrane oxygenation (ECMO) support to refractory shock patients in institutions that do not have MCS capabilities within Paris. Interestingly, the in-hospital mortality of the referred patients was comparable to the outcome of the “in-house” patients.³

Due to recent advances in the field of MCS, treatment strategies are now tailored to various patient profiles. For example, if a cardiogenic shock patient had normal (or presumed normal) heart function in the past, then a “bridge-to-recovery” strategy would be a reasonable option. An example of this might be a patient presenting with an ST elevation myocardial infarction complicated by refractory cardiogenic shock. Aside from providing timely reperfusion and vasoactive medications, a short-term percutaneous MCS device should be initiated as soon as possible for further hemodynamic support. A traditionally used short-term percutaneous MCS device is an intra-aortic balloon pump (IABP). An IABP improves coronary perfusion and decreases afterload, resulting in up to 0.5 liters of cardiac output. However, this is not always adequate to support a failing circulation.^4,5 More current and advanced temporary MCS devices include an Impella system (Abiomed Inc), Tandem Heart system (CardiacAssist Inc.), CentriMag (Thoratec Corp.), or a veno-arterial extracorporeal membrane oxygenation (VA-ECMO). Impella and Tandem Heart are more readily available as they can be placed in the catheterization lab by an interventional cardiologist while the patient is undergoing reperfusion therapy. Compared to IABP, these short-term percutaneous ventricular assist devices (VADs) have produced superior hemodynamic support in patients with refractory cardiogenic shock. However, early experiences with the devices did not translate to better clinical outcomes.⁶

Table 1

Why hemodynamic improvement did not translate into improved clinical outcomes is still a matter of debate. One hypothesis states that the disease processes for some patients were too far advanced to be reversed (“point-of-no-return”). For this subset of patients, a “bridge-to-bridge” strategy might have been appropriate. In this scenario, should a patient’s heart function fail to recover after several days of temporary MCS, a durable VAD could be considered as long as the patient’s other clinical characteristics (i.e., right ventricular [RV] function, age, pulmonary arterial pressure, peripheral organs, neurological status) are satisfactory. Compared to Impella 2.5 (which was used in study), newer devices, such as Impella 5.0 or CP, can generate up to 5.0 or more liters/minute of cardiac output. Recent experience suggests that these VADs could improve the survival in patients with refractory cardiogenic shock; however, large-scale, adequately powered, randomized prospective studies are needed to confirm this (Table 1).^7,8 These devices can be used safely for several days to weeks. A similar approach can be applied for cardiogenic shock patients presenting with acute myocarditis or other etiologies of cardiogenic shock that are considered reversible.

A different approach would be more reasonable if the patient had an underlying heart disease, such as acute decompensation of advanced chronic heart failure. In this case, the progression of cardiogenic shock would be more gradual (from days to weeks). When the patient’s low output state persists despite optimal pharmacological or other non-invasive therapies, durable MCS should be implemented. Unless arrhythmias, infections, or other etiologies (rather than disease progression) are thought to be the reason of the decompensation, the likelihood of cardiac recovery with short-term MCS would be low; in most cases, more durable devices (such as the HeartMate II [Thoratec Inc] or HVAD [HeartWare Inc]) might be better options. If a patient deteriorates rapidly and there is no time to evaluate the patient for candidacy, or if the patient seems to be too ill to undergo a major surgery, a temporary MCS device could be instituted to stabilize the patient (“bridge-to-bridge” or “bridge-to-decision” strategy).

Figure 1

In special circumstances in which the patient has isolated RV failure, biventricular failure, or a concomitant acute respiratory failure, the selection of MCS might need to be modified accordingly. CentriMag (Thoratec Corp.) is a surgically implanted short-term VAD approved as a temporary right ventricular assist device (RVAD) in patients with an acute RV failure. Compared to other short-term percutaneous VADs, it is more durable (repeatedly reported to be used for many weeks) and can provide much higher cardiac output. In cases of respiratory failure, it can also provide ECMO with the addition of an oxygenator. Biventricular failure is a well-known poor prognostic indicator, and mortality is much higher than after univentricular failure. A combination of VADs can be used for biventricular support, but many investigators would advocate VA-ECMO as the preferred option.⁹ Initial experience with an older generation VA-ECMO has been plagued with frightful complications, including surgical trauma, bleeding, infection, and limb ischemia. However, with the technical advances in newer generation VA-ECMO, favorable outcomes have been achieved with fewer complications. VA-ECMO is considered more durable compared to most short-term percutaneous VADs, can support both ventricles, and can be used in the setting of a concomitant respiratory failure (Figure 1).¹

Despite continued efforts to improve clinical outcomes in these critically ill patients, survival remains low at 40-50%. When 90 refractory cardiogenic shock patients from a single institution were studied, half of the patients received short-term VADs while the other half received VA-ECMO support. Reported survival to discharge was 49%; of these patients, 26% required an exchange to durable LVAD support, and 11% required a transplant.¹¹ Therefore, it is imperative that every effort be made to establish a clear endpoint prior to instituting these MCS options. However, due to the acuity of the condition, more often than not a thorough evaluation is not feasible. In addition, a patient incapacitated by critical illness may be unable to participate in shared decision making, thereby shifting this responsibility to family members or a designated healthcare proxy. The hope for reversal of an acute medical condition often leads families toward requesting more aggressive therapies without a full understanding of the potential risks. Due to the high morbidity and mortality of the condition and the aggressive nature of MCS, the patient can often suffer serious complications which might lead one to consider withdrawing care.¹² Published experiences define withdrawal from MCS as morally and ethically appropriate.¹³

To provide the best care for cardiogenic shock patients, it is imperative that device selection and patient management be made by multidisciplinary cardiogenic shock teams in experienced centers.

References:

1. Goldberg RJ, Spencer FA, Gore JM, et al. Thirty-year trends (1975-2005) in the magnitude of, management of, and hospital death rates associated with cardiogenic shock in patients with acute myocardial infarction: a population-based perspective. Circulation 2009;119:1211-9.
2. Nativi-Nicolau J, Selzman CH, Fang JC, et al. Pharmacological therapies for acute cardiogenic shock. Curr Opin Cardiol 2014;29:250-7.
3. Beurtheret S, Mordant P, Paoletti X, et al. Emergency circulatory support in refractory cardiogenic shock patients in remote institutions: a pilot study (the cardiac-RESCUE program). Eur Heart J 2013;34:112-20.
4. Romeo A, Acconcia MC, Sergi D, et al. The outcome of intra-aortic balloon pump support in acute myocardial infarction complicated by cardiogenic shock according to the type of revascularization: a comprehensive meta-analysis. Am Heart J 2013;165:679.
5. Thiele H, Zeymer U, Neumann FJ, et al. Intraaortic balloon support for myocardial infarction with cardiogenic shock. N Eng J Med 2012;367:1287-96.
6. Cheng JM, Uil CA, Hoeks SE, et al. Percutaneous left ventricular assist devices vs. intra-aortic balloon pump counterpulsation for treatment of cardiogenic shock: a meta-analysis of controlled trials. Eur Heart J 2009;30:2102-8.
7. Lemaire A, Anderson M, Lee L, et al. The Impella device for acute mechanical circulatory support in patients in cardiogenic shock. i 2014;97:133-8.
8. Lamarche Y, Cheung A, Ignaszewski A, et al. Comparative outcomes in cardiogenic shock patients managed with Impella microaxial pump or extracorporeal life support. J Thorac Cardiovasc Surg 2011;142:60-5.
9. Dutt DP, Pinney SP. Clinical variability within the INTERMACS 1 profile: implications for treatment options. Curr Opin Cardiol 2014;29:244-9.
10. Ghodsizad A, Koerner MM, Brehm CE, et al. The role of extracorporeal membrane oxygenation circulatory support in the ‘crash and burn’ patient: from implantation to weaning. Curr Opin Cardiol 2014;29:275-80.
11. Takayama H, Truby L, Koekort M, et al. Clinical outcome of mechanical circulatory support for refractory cardiogenic shock in the current era. J Heart Lung Transplant 2013;32:106-11.
12. Drakos S and Uriel N. Spotlight on cardiogenic shock therapies in the era of mechanical circulatory support. Curr Opin Cardiol 2014;29:241-3.
13. Brush S, Budge D, Alharethi R, et al. End-of-life decision making and implementation in recipients of a destination left ventricular assist device. J Heart Lung Transplant 2010;29:1337-41.
14. Thiele H, Zeymer U, Neumann F, et al. Intraaortic balloon support for myocardial infraction with cardiogenic shock. N Eng J Med 2012;367:1287-96.
15. Thiele H, Sick P, Boudriot E, et al. Randomized comparison of intra-aortic balloon support with a percutaneous left ventricular assist device in patients with revascularized acute myocardial infarction complicated by cardiogenic shock. E Heart J 2005;26:1276-83.
16. Burkhoff D, Cohen H, Brunckhorst C, et al. A randomized multicenter clinical study to evaluate the safety and efficacy of the TandemHeart percutaneous ventricular assist device versus conventional therapy with intraaortic balloon pumping for treatment of cardiogenic shock. Am Heart J 2006;152:469.
17. Seyfarth M, Sibbing D, Bauer I, et al. A randomized clinical trial to evaluate the safety and efficacy of a percutaneous left ventricular assist device versus intra-aortic balloon pumping for treatment of cardiogenic shock caused by myocardial infarction. J Am Coll Cardiol 2008;52:1584-8.
18. O’Neill W, Schreiber T, Wohns D, et al. The current use of Impella 2.5 in acute myocardial infarction complicated by cardiogenic shock: Results from the USPella Registry. J Interven Cardiol 2014;27:1-11.
19. Lauten A, Engstrom A, Jung C, et al. Percutaneous left ventricular support with Impella 2.5 assist device in acute cardiogenic shock – results of the Impella EUROSHOCK-Registry. Circ Heart Fail 2013;6:23-30.
20. Combes A, Leprince P, Luyt C, et al. Outcomes and long-term quality-of-life of patients supported by extracorporeal membrane oxygenation for refractory cardiogenic shock. Crit Care Med 2008;36:1404-11.
21. Bermudez C, Rocha R, Toyoda Y, et al. Extracorporeal membrane oxygenation for advanced refractory shock in acute and chronic cardiomyopathy. Ann Thorac Surg 2011;92:2125-31.

Keywords: Arrhythmias, Cardiac, Arterial Pressure, Cardiac Output, High, Critical Illness, Decision Making, Disease Progression, Extracorporeal Membrane Oxygenation, Heart Failure, Heart-Assist Devices, Hospital Mortality, Hypotension, Intra-Aortic Balloon Pumping, Myocarditis, Oxygenators, Respiratory Insufficiency, Shock, Cardiogenic

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