Review Question - QID 100659

This patient presents with chest pain, EKG, and lab findings consistent with an acute myocardial infarction (MI). An acute MI will result in a loss of cardiac contractility with a resulting drop in cardiac output (CO) and a reflexive increase in systemic vascular resistance (SVR).

Myocardial infarctions generally cause a decrease in CO secondary to a loss of function of an area of myocardium. The drop in blood pressure is detected by baroreceptors in the aortic and carotid bodies, resulting in decreased vagal tone. Simultaneously, the drop also results in a medullary response to increase vascular tone. These responses represent the hallmark of cardiogenic shock, mainly a drop in CO (pump failure) and a reflexive increase in SVR.

Incorrect Answers:
Answer 1: Unchanged CO and increased SVR would be expected in someone without the current pathology.
Answer 2: Unchanged CO and decreased venous return can be seen in patients with anaphylaxis. The systemic vasodilation and third-spacing of fluids can cause a marked decrease in venous return.
Answer 4: Decreased CO and decreased venous return can be seen in patients with hypovolemia (e.g., acute hemorrhage).
Answer 5: Increased CO and increased SVR can be seen in patients with sympathomimetic intoxication such as cocaine.

Bullet Summary:
An acute myocardial infarction will result in a drop in cardiac output (CO) and a reflexive increase in systemic vascular resistance (SVR).