CVP Waveform a-Wave — FRCA Primary MCQ
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Correct answer: E — Atrial contraction
The correct answer is E. The a-wave is the rise in right atrial pressure produced by right atrial contraction in late diastole, shortly after the ECG P-wave. Atrial filling while the tricuspid valve is closed produces the v-wave, so A is incorrect. Tricuspid valve opening initiates right atrial emptying and the y-descent; the associated rapid passive right ventricular filling makes B and C incorrect. Early ventricular contraction closes the tricuspid valve and may make it bulge into the right atrium, producing the c-wave, so D is incorrect. Large a-waves occur when atrial contraction meets increased resistance to right ventricular filling; cannon a-waves specifically result from atrial contraction against a closed tricuspid valve during atrioventricular dissociation.
Reference: Del Rio-Pertuz G, Nugent K, Argueta-Sosa E. Right heart catheterization in clinical practice: a review of basic physiology and important issues relevant to interpretation. Figure 2: right atrial waveforms. 2023. https://pubmed.ncbi.nlm.nih.gov/37469534/