Heavily calcified lesions in coronary arteries have been known to cause stent underexpansion, which increases the risk of in-stent restenosis. Plaque modification before stent implantation is considered to be the key for treatment of calcified lesions. We hypothesized that calcium fracture by percutaneous coronary intervention (PCI) might be associated with adequate stent expansion and favorable late outcome.
From the coronary catheterization registry of Wakayama Medical University between February 1, 2010 and August 31, 2013, we retrospectively selected 61 patients with chronic stable angina who had a heavily calcified culprit lesion on coronary angiography. The heavily calcified lesion on coronary angiography was identified by radiopacities noted without cardiac motion before contrast injection, generally compromising both sides of the arterial lumen. Everolimus-eluting stent was used for PCI. PCI procedures including stent size, pre- and post-dilation, and inflation pressure were determined by each physician. Optical coherence tomography (OCT) was performed before and immediately after PCI. Maximal calcium thickness, maximal calcium arc, and maximal calcium length were measured on each candidate frame selected by visual screening in the OCT images before PCI. Calcium fracture and stent expansion were assessed in the OCT images immediately after PCI. Calcium fracture was characterized by a gap of calcium and direct exposure of calcium to the lumen at the gap. The calcium fracture thickness was measured at the edge of the fracture. The minimal stent area was measured on a candidate frame selected by visual screening. Stent expansion index was calculated as the minimal stent area divided by the average of the proximal and distal reference lumen area. Scheduled follow-up angiography was conducted 10 months after PCI.