A central venous pressure trace is obtained from a patient in atrial fibrillation. Compared with a trace in sinus rhythm, what change would be expected?
- A Tall cannon a-waves before each QRS complex
- B Absence of the a-wave with a dominant v-wave ✓
- C Prominent x-descent and absent y-descent
- D Regular sawtooth c-waves at 300 per minute
Correct answer: B. Absence of the a-wave with a dominant v-wave
Explanation
The a-wave reflects right atrial contraction and is therefore absent in atrial fibrillation, leaving the v-wave (atrial filling against a closed tricuspid valve) as the dominant deflection. Cannon a-waves occur when the right atrium contracts against a closed tricuspid valve in junctional rhythms or complete heart block, not in AF where coordinated atrial contraction is lost. The x and y descents remain present, though their timing becomes irregular.
Reference: Morgan and Mikhail's Clinical Anesthesiology, 5th ed.
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Written and medically reviewed by the StethoPrep medical team.