Rosh Emergency Medicine Practice Test

In a patient with ST elevation in leads V1-V3, which hemodynamic parameter is likely to be diminished?

1. Cardiac output

2. Heart rate

3. Pulmonary capillary wedge pressure

4. Systemic vascular resistance

The correct answer is: Cardiac output

In the case of a patient presenting with ST elevation in leads V1-V3, indicative of an anterior wall myocardial infarction (MI), one likely consequence is a diminished cardiac output. This occurs due to impaired contractility of the heart muscle, which can arise from ischemia affecting the left ventricle. When the heart is unable to contract effectively, it directly impacts its ability to pump blood efficiently, thereby reducing the volume of blood (cardiac output) that is ejected during each heartbeat. In an acute myocardial infarction, the damaged myocardium cannot generate the same stroke volume, leading to overall reduced cardiac performance. As a result, the patient may exhibit signs of heart failure, which is often associated with decreased cardiac output. The other parameters, like heart rate, may remain unchanged or even increase in response to the body’s compensatory mechanisms during a myocardial infarction, as the heart tries to maintain perfusion pressure. Pulmonary capillary wedge pressure typically rises due to fluid backing up in the heart, the systemic vascular resistance may also change depending on compensatory responses, but in the setting of diminished cardiac output, it is primarily the cardiac output that reflects the acute hemodynamic impact of the myocardial injury.