Analysis by optical coherence tomography of long-term arterial healing after implantation of different types of stents

Intravascular imaging of angioplasty balloon under-expansion during pre-dilation predicts hyperelastic behavior of coronary artery lesions

Introduction: Stent-induced mechanical stimuli cause pathophysiological responses in the coronary artery post-treatment. These stimuli can be minimized through choice of stent, size, and deployment strategy. However, the lack of target lesion material characterization is a barrier to further personalizing treatment. A novel ex-vivo angioplasty-based intravascular imaging technique using optical coherence tomography (OCT) was developed to characterize local stiffness of the target lesion. Methods: After proper institutional oversight, atherosclerotic coronary arteries (n = 9) were dissected from human donor hearts for ex vivo material characterization <48 h post-mortem. Morphology was imaged at the diastolic blood pressure using common intravascular OCT protocols and at subsequent pressures using a specially fabricated perfusion balloon that accommodates the OCT imaging wire. Balloon under-expansion was quantified relative to the nominal balloon size at 8 ATM. Correlation to a constitutive hyperelastic model was empirically investigated (n = 13 plaques) using biaxial extension results fit to a mixed Neo-Hookean and Exponential constitutive model. Results and discussion: The average circumferential Cauchy stress was 66.5, 130.2, and 300.4 kPa for regions with <15, 15-30, and >30% balloon under-expansion at a 1.15 stretch ratio. Similarly, the average longitudinal Cauchy stress was 68.1, 172.6, and 412.7 kPa, respectively. Consequently, strong correlation coefficients >0.89 were observed between balloon under-expansion and stress-like constitutive parameters. These parameters allowed for visualization of stiffness and material heterogeneity for a range of atherosclerotic plaques. Balloon under-expansion is a strong predictor of target lesion stiffness. These findings are promising as stent deployment could now be further personalized via target lesion material characterization obtained pre-operatively.

Differences in Vessel Healing Between Sirolimus- and Everolimus-Eluting Stent Implantation for Bifurcation Lesions: The J-REVERSE Optical Coherence Tomography Substudy

BACKGROUND

We aimed to clarify the differences in vessel healing after stenting of bifurcation lesions using sirolimus-eluting stents (SESs) or everolimus-eluting stents (EESs).

METHODS

Japanese Registry Study in Comparison Between Everolimus-Eluting Stent and Sirolimus-Eluting Stent for the Bifurcation Lesion (J-REVERSE) is a prospective multicentre registry of 303 bifurcation lesions that were treated with provisional SES or EES with or without final kissing inflation. The first 115 lesions at selected study sites were predefined for inclusion in the optical coherence tomography (OCT) substudy, and 9-month follow-up OCT was conducted in 64 lesions (SES, n = 18; EES, n = 46). In addition to standard OCT parameters, stent eccentricity index (SEI; minimum divided by the maximum stent diameter), neointimal unevenness score (NUS; maximum neointimal thickness in the cross-section [CS] divided by the average neointimal thickness [NIT] of the same CS; uniformity of the neointima suppression) were averaged for each segment (proximal, bifurcation, and distal segments).

RESULTS

Overall, the average stent and luminal area, NIT, and frequency of uncovered struts were similar. The frequency of malapposed struts and SEI were significantly lower in the EES group than in the SES group. The EES group had a significantly smaller NUS in the proximal and distal segments.

CONCLUSIONS

EESs offer homogeneous vessel healing with less malapposition in the treatment of bifurcation lesions.

Neointimal Coverage After Drug-Eluting Stent Implantation: Insights from Optical Coherence Tomography

Optical coherence tomography (OCT), which provides high-resolution imaging of the coronary vasculature, has provided novel insights into the pathophysiology of neointimal growth after drug-eluting stent (DES) implantation. The natural history, time course, and characteristics of strut coverage with neointima have been well defined by OCT. Pathology studies have identified strut coverage as a risk factor for stent thrombosis, and OCT studies have shown that next-generation DES have better strut coverage than first-generation DES. By reducing the incidence of stent thrombosis, improved strut coverage should lead to favorable clinical safety and the feasibility of shorter-duration dual antiplatelet therapy after DES implantation.