The vast majority of patients undergoing percutaneous coronary intervention (PCI) these days are treated with stent insertion uneventfully. Often, in simple cases, pre-dilatation with a balloon is not even performed (so-called “direct” stenting). In more complex cases, varying degrees of resistance of the lesion to balloon expansion are experienced, and these may require multiple balloon pre-dilatations to higher pressure and larger sizes before the stent can be implanted. A truly undilatable lesion is an unpredictable, fearsome and, mercifully, rare finding. It is usually associated with …