Clinical relevance of DES implantation problems highlighted by OCT remains unclear
In a first study of its kind, researchers in Japan using serial optical coherence tomography (OCT) imaging found that patients with unstable and stable angina have markedly different vascular responses to drug-eluting stents, and that those with unstable angina have greater risk of certain complications. The findings, however, were not associated with adverse outcomes in patients taking dual-antiplatelet therapy.

While sirolimus-eluting stents (SES) reduce the need for target-vessel revascularization, they impair local vascular healing with delayed endothelization, the authors wrote. Patients with unstable angina pectoris (UAP), compared to those with stable angina pectoris (SAP), present a greater risk for thrombotic complication after SES implantation, according to a study published in the July issue of JACC Cardiovascular Imaging.

Takashi Kubo, MD, and colleagues from the department of cardiovascular medicine at Wakayama Medical University in Japan, enrolled 55 patients in the study: 24 UAP and 31 SAP. Researchers examined lesion morphologies by using high-resolution (10 to 20 µm) OCT (Image Wire, Light Lab Imaging) at pre- and post-SES (Cypher, Cordis) implantation. The investigators followed the patients out to nine months.

Ten patients refused the angiographic and OCT follow-up. Therefore, the follow-up OCT examination was performed in 18 patients with UAP and 27 patients with SAP.

According to the investigators, the major findings of their analysis were:

  • The incidence of plaque rupture, intracoronary thrombus and thin-capped fibroatheroma (TCFA) (cap thickness <65 µm) in patients with UAP was significantly greater than that in patients with SAP.

  • Although the stent and procedural characteristics were not different between the two groups, the incidence of inadequate stent apposition and tissue protrusion after PCI was significantly greater in patients with UAP.

  • Plaque rupture was significantly increased by PCI in UAP patients, and the residual ruptured plaque at nine months follow-up was observed more frequently in UAP compared to SAP patients.

  • The incidence of inadequately apposed stent and partially uncovered stent by neointima at nine months follow-up was significantly greater in UAP compared to SAP patients.
Researchers found that OCT was able to visualize the inadequate stent features more frequently than when using intravascular ultrasound (IVUS) (Atlantis SR Pro, Boston Scientific).

All patients took aspirin and ticlopidine (Ticlid, Roche Pharmaceuticals) during follow-up period, and no patients had stent thrombosis or adverse coronary events. Furthermore, none of the patients with follow-up coronary catheterization had angiographic restenosis and target vessel revascularization.

The authors cited several previous OCT studies, which support their current findings that OCT can accurately detect fibrous cap disruption in cases of acute MI and that there is a significantly greater prevalence of TCFA in patients with unstable versus stable angina.

“Although OCT is limited in the quantification of lipid-core, it might be a useful modality to evaluate the intrinsic features that determine plaque vulnerability in vivo,” the authors concluded.

IVUS is currently the gold standard to assess coronary intervention. Previous studies have demonstrated the ability of OCT to identify an increased frequency and detail in the detection of small stent features.

“However, these subtle findings by OCT may not be clinically relevant regardless of clinical presentation, lesion characteristics or stent type,” the authors wrote, adding that the quantification or grading of the findings may be important to predict lesion outcomes after PCI.

OCT and IVUS Findings After PCI in UAP and SAP Patients
(A) In the OCT analysis, although the incidence of stent edge dissection was not different between UAP and SAP, the incidence of inadequate stent apposition (*p = 0.038), tissue protrusion (†p = 0.005) and intracoronary thrombus (‡p = 0.001) in UAP was signi?cantly higher than that in SAP. (B) In the IVUS analysis, the incidence of inadequate lesion ?ndings after stenting was similar in both groups. IVUS = intravascular ultrasound; OCT = optical coherence tomography; PCI = percutaneous coronary intervention; SAP = stable anginapectoris; UAP = unstable angina pectoris.