Taylor Hoyt

Diagnosis of Thin-Capped Fibroatheromas in Intravascular Optical Coherence Tomography Images

Background—Intravascular optical coherence tomography (IVOCT) images are recorded by detecting light backscattered within coronary arteries. We hypothesize that non–thin-capped fibroatheroma (TCFA) causes may scatter light to create the false appearance of IVOCT TCFA. Methods and Results—Ten human cadaver hearts were imaged with IVOCT (n=14 coronary arteries). IVOCT and histological TCFA images were coregistered and compared. Of 21 IVOCT TCFAs (fibrous cap <65 &mgr;m, lipid arc >1 quadrant), only 8 were true histological TCFA. Foam cell infiltration was responsible for 70% of false IVOCT TCFA and caused both thick-capped fibroatheromas to appear as TCFA, and the appearance of TCFAs when no lipid core was present. Other false IVOCT TCFA causes included smooth muscle cell–rich fibrous tissue (12%) and loose connective tissue (9%). If the lipid arc >1 quadrant (obtuse) criterion was disregarded, 45 IVOCT TCFAs were identified, and sensitivity of IVOCT TCFA detection increased from 63% to 87%, and specificity remained high at 92%. Conclusions—We demonstrate that IVOCT can exhibit 87% (95% CI, 75%–93%) sensitivity and 92% specificity (95% CI, 86%–96%) to detect all lipid arcs (both obtuse and acute, <1 quadrant) TCFA, and we also propose new mechanisms involving light scattering that explain why other plaque components can masquerade as TCFA and cause low positive predictive value of IVOCT for TCFA detection (47% for obtuse lipid arcs). Disregarding the lipid arc >1 quadrant requirement enhances the ability of IVOCT to detect TCFA.

Translating Intravascular Optical Coherence Tomography from a Research to a Clinical Tool

Intravascular optical coherence tomography (IVOCT) continues to be a hot topic as a method for studying vulnerable plaque in research laboratories across the globe. It is also growing in popularity as a tool for interventional cardiologists to guide percutaneous coronary intervention (PCI). The power of IVOCT for diagnosis of thin-capped fibroatheromas (TCFAs) has yet to receive mainstream clinical attention due to the fact that clinicians still do not have a protocol to follow if TCFA are identified and that TCFA identification requires extensive training in IVOCT image analysis—it is not yet an automated process. In this review, we will discuss the progress of translation of IVOCT from predominantly a research tool to clinical practice by reviewing recent advances in the field of IVOCT for guiding PCI and how the challenge of automated plaque characterization for vulnerable plaque identification is being approached.

Impact of ticagrelor and aspirin versus clopidogrel and aspirin in symptomatic patients with peripheral arterial disease: Thrombus burden assessed by optical coherence tomography

PURPOSE To compare OCT identified white thrombus decline, neointimal hyperplasia and clinical outcomes of patients treated with ticagrelor plus aspirin with those patients treated with clopidogrel plus aspirin after peripheral interventions. BACKGROUND Ticagrelor is a potent platelet inhibitor. In patients with coronary artery disease, ticagrelor and aspirin demonstrated reduced rates of stent thrombosis, compared to aspirin and clopidogrel. The clinical importance of potent antiplatelet inhibition after peripheral endovascular interventions is unknown. METHODS We enrolled 18 patients with superficial femoral artery disease and the presence of OCT-detected clot post-stent placement. Patients were randomized to 75 mg clopidogrel once daily for 1 month vs. 90 mg ticagrelor twice daily for 6 months, both in addition to 81 mg aspirin for 6 months. Clot volumes, ankle-brachial index (ABI), 6-minute walk test, and Rutherford classification were measured at baseline and 6-month follow-up. Neointimal hyperplasia and neovascularization were calculated at 6-month follow-up. RESULTS N = 11 patients were enrolled in the clopidogrel group and N = 7 in the ticagrelor group. There was a significantly greater decrease in white thrombus in the ticagrelor group (median volume/stent length (0.067 vs 0.014 mm3/mm, p = 0.05)). No differences were found in % neointima (0.412 vs 0.536 mm3/mm, p = 0.44) and neovascularization (28 vs 44, p = 0.16). ABI and Rutherford classification were improved significantly after 6 months in the clopidogrel group, with no difference between groups at 6 months in ABI or Rutherford. CONCLUSION In symptomatic patients with PAD, ticagrelor showed significant improvement relative to clopidogrel with respect to white thrombus burden decline.

MECHANISMS FOR FALSE THIN-CAP FIBROATHEROMAS IDENTIFIED BY OPTICAL COHERENCE TOMOGRAPHY

The correct identification of thin-cap fibroatheromas (TCFAs) with optical coherence tomography (OCT) is crucial. Superficial macrophage infiltration and tangential light drop-out are known to cause “false TCFAs.” We identify additional false TCFA mechanisms and quantify the frequency of true

COMPARING TICAGRELOR AND ASPIRIN WITH CLOPIDOGREL AND ASPIRIN IN PATIENTS WITH PERIPHERAL ARTERIAL DISEASE: THROMBUS BURDEN ASSESSED BY OPTICAL COHERENCE TOMOGRAPHY

Claudication is a frequent symptom of peripheral arterial disease (PAD) that limits physical activity. We hypothesized that ticagrelor plus aspirin for 6 months would reduce white thrombus burden post peripheral intervention compared to the current medical standard of care (clopidogrel plus aspirin

Intravascular OCT Imaging Artifacts

This chapter discusses many intravascular imaging artifacts that may be encountered when interpreting OCT images from coronary arteries in the clinic or in research settings. All OCT artifacts originate in either the propagation of light in the vessel lumen, signal acquisition or polar-to-rectangular conversion. When these artifacts are recognized and understood, OCT image interpretation can become much more accurate.

In Situ Quantification and 3D Reconstruction of Thrombus in the Superficial Femoral Artery Disease Using Optical Coherence Tomography

Background: SFA disease accounts for approximately 40% of the symptomatic peripheral artery disease. Atherosclerosis and thrombosis both contribute in the progression of the peripheral arterial disease. Conventional angiography provides little information about the amount of the thrombus burden. Limited data exists on the use of OCT for the evaluation of PAD. Methods: We performed OCT in three patients with SFA disease who underwent peripheral angiogram from January 2011 – December 2014. Using custom-based imaging software we performed 3D reconstruction and quantification of intraluminal thrombus. Results: We identified thrombus formation in all three patients despite absence of evident thrombosis with invasive angiography. The length of the clot ranged from 12.6 - 47.7 mm and the volume from 11.19 - 43.26 mm3). Conclusion: Atherosclerosis and thrombosis both contribute in the progression of the peripheral arterial disease. OCT can accurately quantify the length and the volume of the clot burden. Larger studies are needed to assess their clinical importance in the prevention and management of PAD.