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Physiology · Cardiovascular system: jugular venous pulse
Sample itemA 70-year-old man with an irregularly irregular pulse has no visible 'a' wave in the jugular venous pulse. What is the physiological reason?
Original practice item, not a recalled exam question. Nothing here is recorded.
The answer and the reasoning
C. Loss of effective atrial contraction
The a wave is produced by right atrial contraction at end diastole. In atrial fibrillation there is no coordinated atrial systole, so the a wave disappears. The c wave and v wave arise from other events.
Option by option
A. Tricuspid valve bulging during ventricular systole
Tricuspid bulging produces the c wave, which does not replace the a wave.
B. Raised right ventricular end-diastolic pressure
High right ventricular pressure produces a prominent a wave, not an absent one.
C. Loss of effective atrial contraction (correct)
Correct. Without organised atrial systole there is no a wave.
D. Passive filling of the atrium during systole
Passive atrial filling produces the v wave.
Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.
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