TIL: "Coronary steal" is not the new look of Derek Zoolander, but a physiologic phenomenon caused by vasodilation medications (drugs that make your blood vessels expand). These drugs have a variety of effects on the cardiovascular system but the one you might reasonably think would be useful is opening up the coronary arteries supplying the heart in a patient with athlerosclerotic plaques causing angina (chest pain) which could lead to a myocardial infarction (heart attack). But if you give these drugs to such a person, it will likely make the condition worse.
This counterintuitive result is due to the body being one step ahead of you. When the heart is ischemic (not getting enough nutrients via blood), the body automatically fully dilates the coronary arteries to maximize their blood flow. So, when you prescribe the vasodilator, it has no effect on the coronaries that you were targeting, but still works beautifully on all the other healthier blood vessels in the body. The other vessels widen and divert even more blood away from the coronaries, quite the opposite of the desired effect.
This seemingly nasty side effect (more like downright failure of the drug) actually has a silver lining; by administering this drug class in a controlled setting, you can test the heart's response to ischemic stress. This is one type of cardiac stress test.
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