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 mm(2), P < 0.001) that was greater than the increase in plaque area ( 9.6 +/- 3.0 to 11.4 +/- 2.9 mm(2), 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 approximate to 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.