Ultrasonic and pathological evidence of a neo-intimal plaque rupture in patients with bare metal stents

Case 1 A 58-year-old man was admitted to our coronary care with troponin negative unstable angina. His risk factors included, being an exsmoker for a year, treated hypertension and dyslipidaemia. Medication on admission was aspirin and a statin. ECG showed Twave inversion laterally. Nine years previously he had a bare metal stent implanted in his circumflex artery following a lateral infarction the preceding year. Angiography done during his acute presentation revealed an in-stent restenosis in the previously treated circumflex artery and a diffusely diseased marginal branch. The left anterior decending coronary (LAD) was normal and the right coronary artery (RCA) had a non-flow limiting lesion in the mid-vessel with a fractional flow reserve (FFR) of 0.79. Intravascular ultrasound (IVUS) of the circumflex artery was performed using a 20 MHz Eagle eye IVUS catheter (Volcano Therapeutics, Rancho Cordova, CA, USA). The length of the stented segment was 30mm and had a minimal luminal area (MLA) 4.6 mm2. Neo-intimal formation was visible throughout the stent (Figure 1). This gave a neointimal hyperplasia (NIH) volume of 80.3 mm3. The NIH on virtual histology had a tissue composition of necrotic core (NC) 13.6%, (0.08 mm2, 2.4 mm3), calcified tissue 16.8%, (0.10 mm2, 3.0 mm3), fibrofatty 5.8%, (0.03 mm2, 1.04 mm3), fibrotic tissue 63.9%, (0.38 mm2, 11.5 mm3). Distal to the MLA at distance of 18 mm IVUS revealed an eccentric soft neo-intimal ruptured plaque1,2 (Figure 1C) within the stent. The necrotic core was 22% with remnant plaque burden of 54% at the plaque rupture site (Figure 1 C’). Just distal to ruptured plaque the vessel wall was intact and the plaque burden was higher 65% with no necrotic core in contact with the lumen (Figure 1D”). This ruptured lesion was subsequently managed with a drug eluting stent (DES) that also covered the MLA. The histological findings of a similar plaque rupture are illustrated in Case 2.