Incidence, mechanisms and clinical impact of largely uncovered struts in current generation drug-eluting-stents: insight from the TRANSFORM-OCT Study

Abstract

Background: Thin‐strut drug‐eluting stents (DES) and optimal implantation technique reduce the rate of stent failure significantly. Nevertheless, uncovered struts (US) have been observed as a key factor for stent thrombosis regardless of stent generation and time of follow‐up. Associated factors and temporal evolution are currently unknown. Purpose: To evaluate the prevalence, mechanisms and long‐term clinical impact of largely‐US after state‐of‐the‐art DES implantation in complex coronary clinical/lesion cohorts Methods: The study was a pre‐specified analysis of TRASFORM‐OCT, a randomized controlled trial comparing bioabsorbable or durable polymer DES by serial optical coherence tomography (OCT), obtained at baseline, immediately after procedure, at 3 and 18 months follow‐up. Methods and results were published previously. For the current analysis enrolled patients (n=90) were divided in 2 groups according to the amount of US identified by OCT at 3 months: a largely US (LUS ≥30%) group and the control group (<30% US), to evaluate factors associated to LUS, and the clinical impact at follow‐up. Results: Out of 90 patients, 31 (34.4%) were assigned to the LUS group, and 59 (65.6%) to the control group. At baseline, LUS patients had larger vessels (reference area 5.51±1.1 vs. 4.27±1.5 2, p=0.001), a higher rate of plaque rupture (41.9 vs. 18.6%, p=0.02), thin‐cap fibroatheroma (58.1% vs. 51.7% p=0.03) and thrombus (58.1% vs. 35.6%, p=0.001) as detected by OCT. 98% patients continued dual antiplatelet therapy up to 12 months, and 24% of them up to 18 months. At stent implant, performed with high pressure dilation (21.18±3.8 vs 20.54±3.6 atm in LUS vs control group, p 0.48), the rate of apposed and embedded struts was high in both groups, although higher in controls (93.92±5.30% vs 96.46±3.68%, p 0.03 and 16.8±11.5% vs 21.7±15.8%, p=0.12, respectively for controls and LUS). At 3 months, US rate was 48.4±12% in the LUS group, and 13.3±7% in the control group (p<0.001). Global malapposition rate was 7.95±7.5% and 1.69±1.6% (p<0.001), respectively. 84.52±12.41% of the US in the LUS group and 86.49±19.98% in controls group were apposed to the wall (p 0.07). At 18 months, the rate of US dropped significantly to 8.4±10% in LUS group and 1.8±3% in control group (p<0.001), with malapposition rate being 1.4±3.3 and 0.16±0.43% (p 0.006). Of the US, 81.6±25.15 and 91.11±21.76% were apposed to the wall, respectively. At 5 years clinical follow‐up, no differences were observed at the composite endpoint of major adverse cardiovascular events (detailed data will be presented). Conclusions: In a setting of optimal PCI with modern DES and highpressure inflation, LUS occur in 30% of patients at early follow‐up, more frequently in large vessels with lipid‐rich, complex plaques. The vast majority of US is apposed to the wall and near‐complete coverage is observed at long‐term follow‐up, with no clinical impact compared to subjects with a low rate of US.