Cardiogenic Shock
Cardiovascular shock refers to a hemodynamic state in which the arterial pressure is less than 90/60 mmHg. When this hypotensive state is caused by reduced cardiac output, it is referred to as "cardiogenic" shock. These patients have a reduced cardiac output (cardiac index <2.2 L/min/m2) and a pulmonary capillary wedge pressure >15 mmHg. When cardiac output is reduced, the baroreceptor reflex increases systemic vascular resistance in an attempt to maintain arterial pressure. Therefore, when arterial pressure is reduced and the systemic vasculature is constricted, organ perfusion can become greatly impaired. Reflex tachycardia and cardiac dilation can increase myocardial oxygen demand at the same time coronary blood flow is reduced owing to the reduced arterial pressure. This reduction in the oxygen supply/demand ratio will lead to myocardial ischemia, which can further reduce cardiac performance.
The most common cause of cardiogenic shock is the loss of functioning myocardium following acute myocardial infarction. Heart failure patients who undergo acute compensation are also at risk of cardiogenic shock. Severe valve disease, myocarditis and arrhythymias can also precipitate cardiogenic shock.
Revised 12/16/2009