Abstract 4556: Incidence and Mechanisms of Acute and Late Stent Malapposition After Stent Implantation in Patients With Acute Myocardial Infarction: An Intravascular Ultrasound Substudy of the HORIZONS-AMI Trial
Background. The incidence and mechanisms of stent malapposition (SM) after primary stent implantation in ST-segment elevation myocardial infarction (STEMI) have not been described.
Methods. HORIZONS-AMI was a prospective, dual-arm, factorial, trial in which pts with STEMI were randomized to
unfractionated heparin + GPIIb/IIIa inhibition vs bivalirudin (1:1); and
paclitaxel-eluting TAXUS stents (PES) vs bare metal EXPRESS stents (BMS) (3:1).
A formal IVUS substudy enrolled 241 pts with 263 native coronary lesions (201 PES and 62 BMS) in whom baseline and 13-month follow-up imaging was completed.
Results. Acute SM (ASM) was present in 33.8% PES and 38.7% BMS-treated lesions (p=0.73) and resolved in 13.4% and 14.5% of PES and BMS pts over 13 months (p=0.85). ASM resolution was associated with negative remodeling (r=0.414, p<0.001). An ASM area <1.25mm2 was the best predictor of ASM resolution rather than persistence over 13 months ([AUC]=0.71, p<0.001, 95% CI 0.61– 0.80). At follow-up, late acquired SM (LASM) occurred in 30.8% PES and 8.1% BMS-treated lesions (p<0.001). LASM area correlated with a decrease of peri-stent plaque in lesions without positive remodeling and with an increase in EEM in pts with positive remodeling (Figure⇓). Independent predictors of LASM were plaque or thrombus protrusion after stenting (OR=4.407, 95% CI=1.733 to 11.204) and randomization to PES (OR=4.050, 95% CI=1.477 to 11.111).
Conclusions. In pts with AMI, resolution of ASM is the result of negative remodeling, with larger baseline ASM areas predicting persistent SM. LASM, which is more frequent with PES, is primarily attributable to positive remodeling and/or plaque/thrombus resolution.