USMLE (United States Medical Licensing Examination) Step 1 Practice Exam

Which of the following is a cause of decreased pulse pressure?

1. Aortic regurgitation

2. Obstructive sleep apnea

3. Exercise

4. Hyperthyroidism

The correct answer is: Aortic regurgitation

Decreased pulse pressure is defined as a reduced difference between systolic and diastolic blood pressure. It can occur in conditions where there is a decrease in stroke volume or an increase in peripheral resistance. Aortic regurgitation is a condition characterized by backflow of blood from the aorta into the left ventricle during diastole due to the incomplete closure of the aortic valve. This leads to a higher diastolic pressure while the systolic pressure may not increase as significantly, resulting in a narrowed pulse pressure. In the case of aortic regurgitation, the heart compensates to maintain cardiac output, but the volume overload can lead to a relative decrease in systolic pressure, especially as the condition progresses. Consequently, this can result in a reduced pulse pressure, which is consistent with the option provided. In contrast, obstructive sleep apnea and exercise generally increase pulse pressure due to increased cardiac output and vascular stress, while hyperthyroidism usually results in an increased heart rate and myocardial contractility, often elevating pulse pressure rather than decreasing it.