Serial Intravascular Ultrasound Analysis of the Impact of Myocardial Bridge on Neointimal Proliferation After Coronary Stenting in Patients with Acute Myocardial Infarction

BACKGROUND: Mechanisms underlying the association between myocardial bridge (MB)-stenting and in-stent restenosis (ISR) are still unclear. OBJECTIVE: To assess the impact of MB on ISR using intravascular ultrasound (IVUS). METHODS: In the Harmonizing Outcomes with Revascularization and Stents in Acute Myocardial Infarction (HORIZONS-AMI) trial, 100 left anterior descending artery (LAD) culprit lesions (79 treated with paclitaxel-eluting stents [PES] and 21 treated with bare metal stents) were imaged with serial IVUS immediately postprocedure and at 13 months. RESULTS: At baseline the LAD stent extended into the MB segment beyond the culprit lesion in seven patients (MB-stent group). In the remaining 93 patients the LAD stent was implanted only in the culprit lesion without extending into the MB segment (non-MB-stent group). In PES-treated lesions intimal hyperplasia (IH) was greater in MB-stent group than in non-MB-stent group (1.0 [0.9, 1.3] mm(2) vs. 0.4 [0.2, 0.7] mm(2), P = 0.007). When comparing the MB-stent segment with the non-MB-stent segment in the MB-stent group treated with PES, a significant reduction in lumen area was observed in only the MB-stent segment, owing to an augmented IH within the MB-stent segment (1.56 [1.40, 1.91] mm(2) vs. 0.77 [0.55, 1.23] mm(2) for non-MB-stent segment, P = 0.08), not significant stent recoil (Deltastent area). At follow-up, the minimum lumen area was smaller in the MB-stent group than in the non-MB-stent group (2.9 [2.5, 4.2] mm(2) vs. 5.2 [4.1, 6.7] mm(2), P = 0.02). CONCLUSIONS: Increased incidence of ISR associated with MB-stenting may be attributable to enhanced IH, specific to stented MB segment, not to chronic stent recoil.