Role of Intravascular Imaging for the Diagnosis of Recanalized Coronary Thrombus

Endovascular Detection of Catheter-Thrombus Contact by Vacuum Excitation

OBJECTIVE

The objective of this work is to introduce and demonstrate the effectiveness of a novel sensing modality for contact detection between an off-the-shelf aspiration catheter and a thrombus.

METHODS

A custom robotic actuator with a pressure sensor was used to generate an oscillatory vacuum excitation and sense the pressure inside the extracorporeal portion of the catheter. Vacuum pressure profiles and robotic motion data were used to train a support vector machine (SVM) classification model to detect contact between the aspiration catheter tip and a mock thrombus. Validation consisted of benchtop accuracy verification, as well as user study comparison to the current standard of angiographic presentation.

RESULTS

Benchtop accuracy of the sensing modality was shown to be 99.67%. The user study demonstrated statistically significant improvement in identifying catheter-thrombus contact compared to the current standard. The odds ratio of successful detection of clot contact was 2.86 (p = 0.03) when using the proposed sensory method compared to without it.

CONCLUSION

The results of this work indicate that the proposed sensing modality can offer intraoperative feedback to interventionalists that can improve their ability to detect contact between the distal tip of a catheter and a thrombus.

SIGNIFICANCE

By offering a relatively low-cost technology that affords off-the-shelf aspiration catheters as clot-detecting sensors, interventionalists can improve the first-pass effect of the mechanical thrombectomy procedure while reducing procedural times and mental burden.

A State-Of-The-Art Review on Coronary Artery Border Segmentation Algorithms for Intravascular Ultrasound (IVUS) Images

Intravascular Ultrasound images (IVUS) is a useful guide for medical practitioners to identify the vascular status of coronary arteries in human beings. IVUS is a unique intracoronary imaging modality that is used as an adjunct to angioplasty to view vessel structures using a catheter with high resolutions. Segmentation of IVUS images has always remained a challenging task due to various impediments, for example, similar tissue components, vessel structures, and artifacts imposed during the acquisition process. Many researchers have applied various techniques to develop standard methods of image interpretation, however, the ultimate goal is still elusive to most researchers. This challenge was presented at the MICCAI- Computing and Visualization for (Intra)Vascular Imaging (CVII) workshop in 2011. This paper presents a major review of recently reported work in the field, with a detailed analysis of various segmentation techniques applied in IVUS, and highlights the directions for future research. The findings recommend a reference database with a larger number of samples acquired at varied transducer frequencies with special consideration towards complex lesions, suitable validation metrics, and ground-truth definition as a standard against which to compare new and current algorithms.

Optical Coherence Tomography-OCT for Characterization of Non-Atherosclerotic Coronary Lesions in Acute Coronary Syndromes

Cardiovascular diseases are the main cause of death worldwide, with coronary artery disease being the predominant underlying etiology. The most prevalent coronary lesions are represented by the atherosclerotic plaques, in more than 85% of cases, but there are several other non-atherosclerotic lesions such as spontaneous coronary artery dissection and/or hematoma and spontaneous recanalization of coronary thrombus, which are less common, approximately 5% of cases, but with similar clinical manifestations as well as complications. There are insufficient data regarding the pathological mechanism, true prevalence and optimal treatment of these kind of coronary lesions. Optical coherence tomography (OCT) is an intracoronary imaging technique, developed in order to overcome the diagnostic limitations of a standard coronary angiography and has an extremely high resolution, similar to that of a usual histological evaluation of a biopsy sample, thus, OCT provides a histological-like information, but in a in vivo environment. The aim of this article is to review the current knowledge regarding non-atherosclerotic coronary lesions, with an emphasis on the importance of OCT for optimal identification, characterization of pathogenic mechanisms and optimal treatment selection.

Optical coherence tomography characterization of spontaneous recanalized coronary thrombus - Single center experience

Introduction: Recanalized thrombus is an under diagnosed clinical entity. Aim was to investigate the utility of optical coherence tomography (OCT) in identifying spontaneously recanalized thrombi (SRCT) for management in clinical practice. Methods: This was a retrospective study analyzing 2678 coronary angiograms over a 4-year period which included intravascular imaging guidance in 75.8% of the percutaneous coronary interventions (PCI). Angiographic suspicion of SRCT has hazy appearance seen in 34 patients. Results: Eight patients (7 males and 1 female) were confirmed with SRCT on OCT and two underwent intravascular ultrasound (IVUS). Median age was 52 years (range 33-67 years). Based on clinical symptoms, diagnosis was STEMI-2, NSTEMI-1, unstable angina-3 and chronic stable angina-2. Angiographic patterns were veiled/hazy appearances in 3; braided in 2; pseudo dissection in 2; and near occlusion in 1 patient. OCT findings displayed multiple small cavities, signal-rich with high backscattering and thin septa with smooth inner borders dividing the lumen and intercommunications. Presence of multiple holes conferred typical "Swiss cheese" or 'lotus root' like appearance, characteristic of recanalized thrombi. SRCT lesion length was (median interquartile ranges [IQR], 16.5[12.07-21.5] mm) and minimal luminal area (median [IQR], 1.77 [0.93-3.26] mm²) with significant stenosis (median [IQR], 74.0[67.0-81.0] %). Minimum/maximum number of channels were (median [IQR], 2.0[2.0-2.0]) and (median [IQR], 4.50[4.0-6.75]) respectively. Lipid rich plaque was predominant. IVUS demonstrated echo-lucent channels with small cavities. All but one patient underwent PCI. Conclusion: Intravascular imaging by OCT delineates the characteristics of recanalized thrombi and distinguishes ambiguous lesions. Majority of the lesions involving SRCT were significant both symptomatic and stenosis severity wise on OCT requiring PCI.