Impact of Target Lesion Coronary Calcification on Stent Expansion - An Optical Coherence Tomography Study

Background: Stent underexpansion remains a concern as a cause of drug-eluting stent (DES) failure. Although coronary calcification is considered to be a contributing factor in stent underexpansion, previous intravascular ultrasound studies have failed to demonstrate this relationship. We investigated whether stent expansion could be predicted by coronary calcification as assessed by optical coherence tomography (OCT). Methods and Results: We enrolled 51 de novo native coronary artery lesions treated by a single 2nd-generation DES (3 types). Prior to stent deployment, the arc and area of calcium at the target lesion were measured using OCT. After successful stent implantation, OCT imaging was repeated to assess minimal stent diameter and area (MSD and MSA). Stent expansion was defined as MSD (or MSA) divided by the values predicted by the manufacturers' compliance charts. Patients were divided into 4 groups according to the median values of the arc and area of calcium. Mean stent expansion was 73.3 +/- 8.7% for MSD and 65.2 +/- 12.0% for MSA. Stent expansion defined by MSD was significantly different among the 4 groups (P=0.02). A similar trend was observed for stent expansion defined by MSA (P=0.16). Conclusions: The extent of target lesion calcification as assessed by OCT may be an important determinant of the expansion of 2nd-generation DES.