Use of DES is reasonable when PCI is indicated in patients with an aorto-ostial stenosis.746,747 (Level of Evidence: B) Aorto-ostial stenoses of native coronary arteries (left main coronary artery and right coronary artery) are most com- monly caused by atherosclerosis, but they can also occur in patients with congenital malformations, radiation exposure, vasculitides, and aortic valve replacement. The angiographic diagnosis of aorto-ostial disease is not always straightfor- ward, especially in the ostial left main coronary artery, where eccentricity and angulation can be mistaken for stenosis.490,748 Aorto-ostial disease can be evaluated with IVUS744,745; FFR (with IV adenosine) has also been used.484,749 The treatment of aorto-ostial stenoses with balloon angioplasty has been associated with lower procedural success rates, more frequent in-hospital complications, and a greater likelihood of late restenosis.750 Although atherectomy devices (directional atherectomy, rotational atherectomy, and excimer laser an- gioplasty) have improved acute angiographic results over balloon angioplasty, restenosis has remained a limitation.751 In patients with aorto-ostial stenoses undergoing PCI, use of DES has been shown to reduce restenosis compared with 5.8.5. Calcified Lesions: Recommendation Class IIa 1. Rotational atherectomy is reasonable for fibrotic or heavily calcified lesions that might not be crossed by a balloon catheter or adequately dilated before stent implantation.514,515,520 (Level of Evidence: C) The presence of coronary calcification is a marker for significant CAD and increased long-term mortality.753 Calci- fied coronary lesions are not a homogenous entity, and their response to PCI varies according to severity of calcification. 