Arterial Waveform Interpretation — FRCA Final MCQ

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HardAnaesthetic Equipment & SafetyArterial Waveform InterpretationFRCA Final

A patient in the ICU has a radial arterial cannula. The transducer is correctly levelled and zeroed, and a fast-flush test confirms an appropriately damped measurement system. Over several cardiac cycles, the arterial waveform has a prolonged, shallow systolic upstroke with an anacrotic shoulder and a delayed, rounded systolic peak. Which haemodynamic condition is most consistent with this waveform?

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Correct answer: B — Severe aortic stenosis

The correct answer is **D, severe aortic stenosis**. Fixed left ventricular outflow obstruction slows systolic ejection, producing a prolonged arterial upstroke and delayed, rounded peak—the waveform correlate of pulsus tardus. An anacrotic shoulder may also occur. In a radial waveform, delayed upstroke is more reliable than reduced pulse pressure for identifying severe stenosis. Hypovolaemia primarily reduces waveform amplitude and pulse pressure and, under suitable conditions, increases respiratory pulse-pressure variation; it does not characteristically cause a fixed delayed peak. Septic vasodilation tends to produce a brisk, hyperdynamic waveform with reduced wave reflection. Severe aortic regurgitation produces a rapid upstroke, wide pulse pressure and rapid diastolic runoff. Confirmation that the monitoring system is appropriately damped excludes overdamping as an explanation for the slow, blunted contour.

Reference: Yoshioka N et al. Do radial arterial pressure curves have diagnostic validity for identify severe aortic stenosis? Journal of Anesthesia. 2010;24:50-55. https://pubmed.ncbi.nlm.nih.gov/20175282/