DOI: 10.1097/01.CCM.0000208327.13731.75

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PMID: 16550075

Issn Print: 0090-3493

Publication Date: 2006/04/01


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Cardiogenic shock: Giving the heart a break*

Janah Aji; Steven Hollenberg

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Over the past 3 decades, the short-term and long-term mortality of ST-elevation myocardial infarction (MI) has improved remarkably, from about 19% in the mid-1980s (1) to <5% in some of the most recent registries and trials (2–4). The main reason for this progress appears to be improved and more efficient reperfusion strategies (2). Despite the remarkable improvement in survival, the incidence of cardiogenic shock, one of the most lethal complications of acute MI, remains steady at 5% to 10% (5–7). The likely explanation is that a decrease in the incidence of cardiogenic shock per surviving patient is balanced by more patients with cardiogenic shock surviving the initial event, maintaining the overall incidence somewhere around 7% to 8% (6, 7).
Despite the complex underlying pathophysiology and clinical variability of cardiogenic shock, the result is low cardiac output, tissue hypoperfusion, and high mortality (8). Early revascularization, along with inotropic support and intra-aortic balloon pumping, has been shown to improve the 6-month mortality from 63% to about 50% (7). In this issue of Critical Care Medicine, Chen and colleagues (9) studied 36 patients with advanced cardiogenic shock, resulting in cardiac arrest and the need for resuscitation, a group for which the predicted mortality is >90% (10). They included mostly patients after prolonged cardiopulmonary resuscitation (CPR) (46 ± 18 mins); all patients received intra-aortic balloon pumps and a high dose of inotropic medications. Patients were stabilized hemodynamically by rapidly receiving extracorporeal life support (ECLS) for an average of 4.5 days, during which they underwent revascularization therapy with percutaneous coronary intervention (PCI) in 11 patients and coronary artery bypass grafting (CABG) in 28 patients. Remarkably, 70% (25 patients) were able to be weaned off ECLS, with 50% (18 patients) surviving for more than 30 days and 33% (12 patients) being discharged from the hospital. Although it seems that Chen and colleagues selected a very sick group of patients, the coronary atherosclerosis burden is similar to that reported in other trial reports (7). The high lactic acid levels and the prolonged CPR times in this group prove the advanced stage of cardiogenic shock these patients were in and brings to mind the concept that ECLS can bring some patients “back from irreversibility” (11).
The principle behind ECLS involves obtaining access to drain the blood from the venous circulation into an extracorporeal circuit, where it is oxygenated and cleansed of carbon dioxide and returned to the circulation to maintain perfusion to the brain, kidneys, and other vital organs. Nearly 29,000 patients have received extracorporeal circulation life support for various reasons. ECLS has become an accepted therapy for children and adults with reversible cardiac and respiratory failure, with a proven benefit for short- and long-term survival (12, 13), and most of the patients reported so far have been neonates and children with respiratory failure. Its use in adults with cardiac failure is increasing, and the overall survival rate is about 33% (14).
Three indications for ECLS in acute MI have been well-studied: first, for supported high-risk PCI in acute MI (15, 16); second, in patients with cardiogenic shock, to allow time for recovery of stunned myocardium (17), as a bridge for revascularization therapy (18), or as a bridge for cardiac transplant (19); and third, as a rescue measure in patients with ongoing CPR for cardiac arrest (20–22). Elective use of ECLS for high-risk PCI gained popularity in the early 1990s but subsequently fell out of favor owing to quicker and more efficient intervention and much improved PCI equipment; no benefit was shown for ECLS over intra-aortic balloon pump support in the elective setting (23).
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