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Content Update: Cardiogenic Shock - May 2022
Text and references have been updated throughout in keeping with contemporary reports. See the section on Hypotension, and Table 50-4 for new information on vasopressors. Mechanical complications associated with cardiogenic shock are discussed in the section “Physical Examination”.
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INTRODUCTION AND EPIDEMIOLOGY
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Cardiogenic shock results from decreased cardiac output, leading to inadequate tissue perfusion despite adequate circulating volume, and it carries an in-hospital mortality rate of 27% to 51%.1,2 While the true incidence is unknown due to missing data from out-of-hospital associated deaths, cardiogenic shock occurs in up to 10% of patients with ST-segment elevation myocardial infarction (STEMI) and is the leading cause of in-hospital death in patients with acute myocardial infarction (AMI).3-6,63 Cardiogenic shock occurs less frequently (2.5%) in those with non–ST-segment elevation myocardial infarction (NSTEMI).7,8 Only approximately 10% of AMI patients who will develop cardiogenic shock have it at initial ED presentation. With the median time of onset after ED arrival being 6 hours, prompt recognition and rapid intervention are essential.9,66 A strategy of early revascularization (percutaneous coronary intervention or coronary artery bypass surgery), mechanical circulatory support device when indicated, and optimal medical therapy, portend the best outcomes.3,10-13 The more individual risk factors (Table 50-1), and the greater amount of vulnerable myocardium, the greater the risk of cardiogenic shock.67 Cardiogenic shock is difficult to diagnose due to its diverse presentations, overlap with other shock states, multifactorial causes that may not be ischemic in nature, and variability in presenting hemodynamics.
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Despite advances in pharmacologic and device-based approaches for patients with cardiogenic shock, only small improvement in mortality has been observed over the past decade. Limited randomized controlled trials have failed to show clear superiority of recommended therapeutic strategies in part due to the heterogeneity of trial and registry data.
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The most common cause of cardiogenic shock is extensive myocardial infarction that depresses myocardial contractility. Additional causes are listed in Table 50-2. Regardless of the precipitating cause, cardiogenic shock is primarily “pump failure,” resulting in diminished cardiac output, hypotension, systemic vasoconstriction, and increasing cardiac ischemia.14 The systolic blood pressure drops due to poor cardiac output, causing hypoperfusion of vital organs. Without a rise in systemic vascular resistance, the diastolic blood pressure drops, resulting in coronary artery hypoperfusion. This creates a deadly cycle of worsening myocardial ischemia and pump dysfunction and ...