A 50-year-old African American gentleman presents to the Emergency Department with sudden onset “vice-like” chest pain, diaphoresis, and pain radiating to his left shoulder. He has ST elevations on his EKG and elevated cardiac enzymes. Concerning his current pathophysiology, what would be the expected cardiac output and venous return changes seen in this patient?
1.No change in cardiac output;increased systemic vascular resistance
2.No change in cardiac output; decreased venous return
3.Decreased cardiac output increased systemic vascular resistance
4.Decreased cardiac output; decreased venous return
5.Increased cardaic output; increased systemic vascular resistance
summary
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, and a reflexive increase in systemic vascular resistance.
Myocardial infarctions generally cause a decrease in cardiac output (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, resulting in chronotropy and inotropy. 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 cardiac output (pump failure) and a reflexive increase in systemic vascular resistance.
McConaghy and Oza discuss acute chest pain syndromes. Gastroesophageal reflux disease, costochondritis, and chest wall pain are three very common causes of chest pain. Less common, but still extremely important causes of chest pain include pericarditis, pneumonia, pulmonary embolism, and myocardial infarction. Each diagnosis presents with subtle differences, and it is of utmost importance to be able to tease out the intricacies of each in order to make the correct diagnosis.
Boateng and Sanborn review myocardial infarctions. The initial evaluation of a patient with a suspected acute myocardial infarction should include a focused history and physical, EKG, cardiac markers, and a chest radiograph. Myocardial infarctions take place when there is decreased myocardial perfusion sufficient enough to cause necrosis. The most common cause is a coronary thrombus. Rupture of atherosclerotic plaques can be thrombrogenic and lead to acute MIs. The main goals of treatment are pain relief and reperfusion in order to maintain appropriate hemodynamic stability.
Illustration A depicts a cardiac function curve. Be able to understand how each parameter changes with varying diseases.