Chapter 54

Cardiogenic shock is an acute state of decreased cardiac output resulting in inadequate tissue perfusion despite adequate or excessive circulating volume. Cardiogenic shock remains the leading cause of death in patients with acute myocardial infarction (AMI) who reach the hospital alive. The precise overall incidence of cardiogenic shock is difficult to ascertain because patients who die before hospital presentation are not given the diagnosis. However, for those who reach the hospital alive, the incidence is approximately 6% to 8%, and has remained constant for the past three decades.1–3 During the past decade, a strategy of early revascularization, either by percutaneous coronary intervention or coronary artery bypass surgery, has proven superior to initial aggressive medical therapy.4–6 Despite these advances, once cardiogenic shock is diagnosed, the mortality remains high (~50%), with half of the deaths occurring within the first 48 hours after presentation.7–9

Risk factors for cardiogenic shock are listed in Table 54-1. The more risk factors that present, the greater the amount of vulnerable myocardium and the greater the likelihood of cardiogenic shock. Early identification of increased risk may suggest more aggressive reperfusion strategies to prevent cardiogenic shock.

Table 54-1 Risk Factors for Cardiogenic Shock

The most common cause of cardiogenic shock is extensive myocardial infarction (MI) with subsequent depression of myocardial contractility. Additional causes are listed in Table 54-2. Regardless of the precipitating cause, the majority of cardiogenic shock is associated with pump failure, which initiates a vicious cycle of reduced cardiac output, blood pressure (BP), and coronary artery hypoperfusion, which potentiates a further decline in contractility and cardiac output.

Table 54-2 Causes of Cardiogenic Shock

The classic shock paradigm predicts that acute reduction in cardiac output leads to compensatory vasoconstriction, and that systemic vascular resistance (SVR) should rise in response to the impaired cardiac output. However, the SHOCK trials and registry demonstrated that the average SVR was not elevated in cardiogenic shock patients, even with vasopressor use.10 Furthermore, the average left ventricular (LV) ejection fraction (EF) was found to be only moderately ...

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