Incidence, Mechanism, Predictors, and Long-Term Prognosis of Late Stent Malapposition after Bare-Metal Stent Implantation

Background - Predictors and long-term prognosis of late stent malapposition (LSM) after bare-metal stent (BMS) implantation are unknown. Methods and Results - We evaluated the incidence, mechanisms, predictors, and long-term prognosis of LSM after BMS implantation in 881 patients (992 native lesions) in whom intravascular ultrasound was performed at index and 6-month follow-up. LSM was defined as a separation of stent struts from the intimal surface of the arterial wall that was not presented at stent implantation. LSM occurred in 54 patients with 54 lesions (5.4% overall); the incidence was 10.3% (9 of 87) after directional coronary atherectomy (DCA) before stenting and 11. 5% (11 of 96) after primary stenting in acute myocardial infarction (P=0.031 and P=0.007, respectively, versus elective stenting with conventional balloon pre-dilation, 4.3% [30 of 692]). There was an increase of external elastic membrane area (18.9±3.9 to 24.5±5.1 mm², P<0.001) that was greater than the increase in plaque area (9.6±3.0 to 11.4±2.9 MM², P<0.001). Independent predictors of LSM were primary stenting in acute myocardial infarction (P=0.023, OR=2.55, 95% CI=1.14 to 5.69) and DCA before stenting (P=0.025, OR=3.02, 95% CI=1.15 to 7.96). There were no significant differences in major adverse cardiac events between LSM and non-LSM groups during mean 3-year follow-up (1.9% versus 1.8%, respectively, P=NS). Conclusions - LSM occurs in ≈5% after BMS implantation. The predictors of LSM are primary stenting in acute myocardial infarction and DCA before stenting. Compared with complete stent apposition at follow-up, LSM after BMS implantation is not associated with any major adverse cardiac events during a mean 3-year follow-up after detection of LSM.