Mechanisms of late stent malapposition after primary stenting in ST-elevation myocardial infarction: a subanalysis of the selection trial.

Background: One of the major predictors of late stent malapposition (LSM) is primary stenting in acute myocardial infarction. However, mechanisms of LSM are still under debate.

Methods: Patients with ST-elevation myocardial infarction (STEMI) and enrolled in the SELECTION trial (38 patients in the paclitaxel-eluting stent, PES, and 35 in the bare metal stent, BMS, cohort) were retrospectively analyzed to evaluate LSM, by means of intravascular ultrasound (IVUS) data recorded at the index and 7-month follow-up procedures.

Results: Stent malapposition was documented in 21 lesions in 21 patients (28.8%): in 8 of these 21 patients (38.1%) it was LSM. Although statistical significance was not reached, LSM was more frequent after PES than BMS implantation (15.8% vs. 5.7%). LSM was mainly located within the body of the stent (62.5% of the cases). At the LSM segment, a significant increase of vessel area (19.2 +/- 3.3 mm(2) vs. 21.9 +/- 5.3 mm(2), P = 0.04) and a reduction of plaque area (12.6 +/- 4.6 mm(2) vs. 9.1 +/- 3.9 mm(2), P = 0.04) were observed at IVUS between the index and follow-up procedure.

Conclusions: After primary stenting for STEMI, LSM seems to be more frequent after PES rather than BMS implantation. In the STEMI setting, possible mechanisms leading to LSM include positive remodeling and plaque mass decrease.