A 72-year-old man is brought to the hospital due to severe substernal chest pain and shortness of breath for the last several hours. The pain started suddenly when he was outside working in the garden. Medical history includes diet-controlled diabetes mellitus and hypertension. Physical examination reveals bilateral crackles and a third heart sound. ECG shows ST elevation in multiple leads. The patient is diagnosed with an acute myocardial infarction complicated by acute severe heart failure. He is started on dobutamine infusion and prepared for coronary catheterization. Which of the following is most likely to be increased due to the medication used in this patient?

Question

A 72-year-old man is brought to the hospital due to severe substernal chest pain and shortness of breath for the last several hours.  The pain started suddenly when he was outside working in the garden.  Medical history includes diet-controlled diabetes mellitus and hypertension.  Physical examination reveals bilateral crackles and a third heart sound.  ECG shows ST elevation in multiple leads.  The patient is diagnosed with an acute myocardial infarction complicated by acute severe heart failure.  He is started on dobutamine infusion and prepared for coronary catheterization.  Which of the following is most likely to be increased due to the medication used in this patient?

Quizplus · Accepted Answer

11ec160b_3b82_297f_9249_2545bb51be70_MD0001_00 Dobutamine is a beta adrenergic agonist with predominant activity on beta-1 receptors, weaker activity on beta-2 receptors, and minimal activity on alpha-1 receptors. It is used for management of refractory heart failure associated with severe left ventricular systolic dysfunction and cardiogenic shock. Stimulation of beta adrenergic receptors results in increased production of cAMP in target cells and causes the following effects: Positive inotropy and chronotropy: Increased cardiac contractility (potent effect) and heart rate (weaker effect), leading to increased cardiac output (improves end-organ perfusion) and decreased left ventricular filling pressures (improves pulmonary congestion/edema) Mild vasodilation: Decreased systemic vascular resistance that often causes a slight reduction in blood pressure; this avoids the increase in afterload seen with other vasopressor/inotropic agents (eg, norepinephrine) but limits its usefulness in severely hypotensive patients The strong inotropic effect of dobutamine significantly increases myocardial oxygen consumption, which can trigger or exacerbate myocardial ischemia. As such, dobutamine should not be used routinely in patients with decompensated heart failure. However, in patients with cardiogenic shock, this drawback is often outweighed by improvement in cardiac output and end-organ perfusion. (Choice A) Dobutamine is a weak chronotropic agent that causes an increase in heart rate. This leads to a decrease in cardiac diastolic filling time. (Choice C) In the vasculature, the beta-2 agonist effects (vasodilation) of dobutamine are somewhat stronger than its alpha-1 agonist activity (vasoconstriction), resulting in overall mild vasodilation. The net hemodynamic effects are a decrease in systemic vascular resistance with or without a slight reduction in blood pressure. (Choices D and E) Dobutamine causes decreased pulmonary capillary wedge pressure and left and right ventricular filling pressures due to the increased cardiac contractility and output. Educational objective: Dobutamine is a beta adrenergic agonist with predominant activity on beta-1 receptors. It causes an increase in heart rate and cardiac contractility, leading to an increase in myocardial oxygen consumption. __________ References: Dobutamine in left heart failure after acute myocardial infarction. (http://www.ncbi.nlm.nih.gov/pubmed/506801) A review of cardiogenic shock in acute myocardial infarction. (http://www.ncbi.nlm.nih.gov/pubmed/19924275)

A 72-Year-Old Man Is Brought to the Hospital Due to Severe