Pulsus alternans is seen in: March 2009
**Core Concept**
Pulsus alternans is a physical examination finding characterized by alternating strong and weak pulses in a patient's radial or carotid arteries. This phenomenon is typically associated with severe left ventricular failure, where the left ventricle is unable to generate a consistent pressure wave to propel blood forward.
**Why the Correct Answer is Right**
The alternating pulses in pulsus alternans are due to the left ventricle's inability to maintain a consistent stroke volume, resulting in a beat-to-beat variation in blood pressure. This can be attributed to the left ventricle's reduced contractility, often seen in conditions such as heart failure with reduced ejection fraction (HFrEF). As the left ventricle contracts, it generates a strong pulse, but in the subsequent beat, it fails to contract adequately, leading to a weak pulse.
**Why Each Wrong Option is Incorrect**
**Option A:** Pulsus alternans is not typically seen in patients with atrial fibrillation, as the irregular heart rhythm does not allow for the consistent beat-to-beat variation characteristic of pulsus alternans.
**Option B:** While pulsus bigeminus is a related phenomenon, it is characterized by a strong pulse followed by a premature, weak pulse, whereas pulsus alternans involves alternating strong and weak pulses in a more regular rhythm.
**Option C:** Pulsus paradoxus is a different physical examination finding, where there is a greater than 10 mmHg decrease in systolic blood pressure during inspiration, typically seen in conditions such as severe asthma or cardiac tamponade.
**Clinical Pearl / High-Yield Fact**
Remember that pulsus alternans is a sensitive but not specific sign of left ventricular failure, and its presence should prompt further evaluation of the patient's cardiac function.
**Correct Answer: C. Pulsus alternans is seen in severe left ventricular failure.**