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More patients admitted with acute myocardial infarction (MI) could be saved if cardiogenic shock (CS) was prevented, concludes a review.
Early recognition of cardiogenic shock is crucial but tricky, the authors say. Decreased peripheral blood flow despite sufficient blood volume indicates CS, and in the time around infarction sustained hypotension and decreased peripheral blood flow. However, signs can vary. In particular, patients with anterior MI and tissue hypoxia but normal blood pressure should be assumed to have CS. This pre-shock state has a very poor prognosis; if unrecognised and treated with β blockers it will precipitate overt CS.
The causes of CS are left ventricular fibrillation—the most common—right ventricular fibrillation, and mechanical failure. In trials early revascularisation significantly improves survival, but only in patients under 75, and this is the treatment strategy endorsed by the ACC/AHA. The immediate priorities are resuscitation and maintaining arterial pressure. Aspirin and full dose heparin should be given. IABP is indicated for patients with ST elevation MI needing angiography and glycoprotein IIb/IIIa inhibitor for non-ST elevated MI.
Then judging the state of the heart and cardiac vessels is the crux of treatment—a task for a tertiary referral centre—and patients should be supported with prophylactic IABP before and during transfer. The classic anatomical picture is of triple vessel disease, left main disease, and decreased left ventricular function.
CS often goes unrecognised, and though it often occurs soon after MI, many patients with ST or non-ST elevation MI die as a result.