Long-term follow-up of attenuated plaques in patients with acute myocardial infarction: an intravascular ultrasound substudy of the HORIZONS-AMI trial

Abstract

Background: Intravascular ultrasound (IVUS)-attenuated plaque is characterized by absence of ultrasound signal behind hypoehcoic plaque and is seen almost exclusively in acute coronary syndromes.

Methods and results: We analyzed poststenting and 13-month follow-up IVUS in 186 patients (195 lesions) with acute myocardial infarction who underwent primary percutaneous coronary intervention. The primary prespecified IVUS end point was the in-stent percent net volume obstruction at follow-up. Overall, 70.3% of lesions contained attenuated plaques at baseline. During follow-up, attenuation scores decreased significantly, behind paclitaxel-eluting stents (PES) (14.1 [11.9, 16.3] to 7.7 [5.4, 9.9], P<0.0001), behind bare metal stents (BMS) (18.5 [13.2, 23.8] to 12.0 [6.7, 17.3], P<0.0001), and within distal references (3.1 [1.1, 5.1] to 2.2 [0.2, 4.1], P=0.02). There was a greater calcium increase in attenuated than nonattenuated plaques in both PES (Δcalcium score of 4.4 [3.3, 5.5] versus 1.6 [0.9, 2.3], P<0.0001) and BMS (Δcalcium score of 4.1[2.3, 5.9] versus 1.0 [0.3, 1.7], P=0.001). PES implantation into attenuated plaques was particularly associated with late acquired stent malapposition (36.8% versus 15.4% compared with nonattenuated plaques treated with PES, P=0.03). Changes in attenuation scores correlated with changes in calcium scores both in PES (Pearson correlation coefficient=-0.456, P<0.0001] and BMS sites (Pearson correlation coefficient=-0.450, P=0.0006). In 3 years of follow-up, target lesion revascularization was significantly less in patients with attenuated plaque at baseline (6.0% versus 17.4% in patient without attenuated plaques, P=0.019).

Conclusions: Attenuated plaques evolved into calcified plaques after stent implantation. Attenuated plaque is associated with late acquired stent malapposition and related less target lesion revascularization (consistent with less neointimal hyperplasia), especially after PES implantation in patients with acute myocardial infarction.

Clinical trial registration: URL: http://www.clinicaltrials.gov. Unique identifier: NCT00433966.