AbstractA 56‐year‐old female, who underwent aortocoronary bypass graft for occlusion of anterior descending artery is reported, who postoperatively developed a harsh systolic murmur, mitral regurgitation, and intraventricular systolic pressure gradient suggestive of hypertrophic subaortic stenosis. The above findings were due to the administration of dobutamine hydrochloride for hypotension in association with afterload reduction (intra‐aortic balloon pumping) and disappeared almost immediately after left ventriculography (volume load).