skip to main content

Coronary Steal — FRCA Primary MCQ

Instant feedback + full explanation. One question, done properly.

HardPharmacology - Inhalational AgentsCoronary StealFRCA Primary

In a patient with a critical proximal coronary stenosis, distal resistance vessels are already maximally dilated and the affected myocardium is dependent on collateral flow. An inhalational anaesthetic dilates resistance vessels in normally perfused coronary territories, theoretically redistributing collateral flow away from the ischaemic region. Which agent was classically implicated in the resulting coronary-steal controversy, although later controlled studies did not confirm a clinically important steal effect when haemodynamics were maintained?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — Isoflurane

Isoflurane was the agent classically associated with coronary steal. The proposed mechanism was preferential dilatation of resistance vessels in normally perfused myocardium, lowering collateral driving pressure to an ischaemic territory whose arterioles were already maximally dilated. However, later clinical and experimental work did not demonstrate clinically important isoflurane-induced steal when arterial pressure and heart rate were controlled. Sevoflurane and desflurane also dilate coronary resistance vessels at high concentrations, so an unqualified question asking which agent is simply “most likely” is insufficiently precise. Halothane predominantly causes myocardial depression and was not the focus of the classic controversy. Nitrous oxide is not a potent volatile coronary vasodilator. Clinically, preservation of coronary perfusion pressure and avoidance of tachycardia remain more important than the historical attribution.

Reference: Crystal GJ. Isoflurane and the Coronary Steal Controversy of the 1980s: Origin, Resolution, and Legacy. Journal of Anesthesia History. 2017;3(2):56-62. https://pubmed.ncbi.nlm.nih.gov/28641827/