Current status of hybrid intravascular ultrasound and optical coherence tomography catheter for coronary imaging and percutaneous coronary intervention

State-of-art review: intravascular imaging in percutaneous coronary interventions

The history of intravascular ultrasound (IVUS) and optical coherence tomography (OCT) reflects the relentless pursuit of innovation in interventional cardiology. These intravascular imaging technologies have played a pivotal role in our understanding of coronary atherosclerosis, vascular pathology, and the interaction of coronary stents with the vessel wall. Two decades of clinical investigations demonstrating the clinical efficacy and safety of intravascular imaging modalities have established these technologies as staples in the contemporary cardiac catheterization lab's toolbox and earning their place in revascularization clinical practice guidelines. In this comprehensive review, we will delve into the historical evolution, mechanisms, and technical aspects of IVUS and OCT. We will discuss the expanding evidence supporting their use in complex percutaneous coronary interventions, emphasizing their crucial roles in optimizing patient outcomes and ensuring procedural success. Furthermore, we will explore the substantial advances that have propelled these imaging modalities to the forefront of contemporary interventional cardiology. Finally, we will survey the latest developments in the field and explore the promising future directions that have the potential to further revolutionize coronary interventions.

Plaque burden estimated from optical coherence tomography with deep learning: In vivo validation using co-registered intravascular ultrasound

OBJECTIVES

The objective of the present study was to compare plaque burden (PB) calculated from optical coherence tomography (OCT) using deep learning (DL) with PB derived from co-registered intravascular ultrasound (IVUS).

BACKGROUND

A DL algorithm was developed for automated plaque characterization and PB quantification from OCT images. However, the performance of this algorithm for PB quantification has not been validated.

METHODS

Five-year follow-up OCT and IVUS images from 15 patients implanted with bioresorbable vascular scaffold (BVS) at baseline were analyzed. Precise co-registration for 72 anatomical slices was achieved utilizing unique BVS radiopaque markers. PB derived from OCT DL and IVUS were compared. OCT cross-sections were divided into four subgroups with different media visibility level. The impact of media visibility on the numerical difference between OCT-derived and IVUS-derived PB was investigated. The stent sizes selected by OCT DL and IVUS were compared.

RESULTS

Sixty-four paired OCT and IVUS cross-sections were compared. OCT DL showed good concordance with IVUS for PB assessment (ICC = 0.81, difference = -3.53 ± 6.17%, p < 0.001). The numerical difference between OCT DL-derived PB and IVUS-derived PB was not substantially impacted by missing segments of media visualization (p = 0.21). OCT DL showed a diagnostic accuracy of 92% in identifying PB > 65%. The stent sizes selected by OCT DL were smaller compared to the ones selected by IVUS (difference = 0.30 ± 0.34 mm, p < 0.001).

CONCLUSIONS

The DL algorithm provides a feasible and reliable method for automated PB estimation from OCT, irrespective of media visibility. OCT DL showed good diagnostic accuracy in identifying PB > 65%, revealing its potential to complement conventional OCT imaging.

Human Coronary Plaque Optical Coherence Tomography Image Repairing, Multilayer Segmentation and Impact on Plaque Stress/Strain Calculations

Coronary vessel layer structure may have a considerable impact on plaque stress/strain calculations. Most current plaque models use single-layer vessel structures due to the lack of available multilayer segmentation techniques. In this paper, an automatic multilayer segmentation and repair method was developed to segment coronary optical coherence tomography (OCT) images to obtain multilayer vessel geometries for biomechanical model construction. Intravascular OCT data were acquired from six patients (one male; mean age: 70.0) using a protocol approved by the local institutional review board with informed consent obtained. A total of 436 OCT slices were selected in this study. Manually segmented data were used as the gold standard for method development and validation. The edge detection method and cubic spline surface fitting were applied to detect and repair the internal elastic membrane (IEM), external elastic membrane (EEM) and adventitia-periadventitia interface (ADV). The mean errors of automatic contours compared to manually segmented contours were 1.40%, 4.34% and 6.97%, respectively. The single-layer mean plaque stress value from lumen was 117.91 kPa, 10.79% lower than that from three-layer models (132.33 kPa). On the adventitia, the single-layer mean plaque stress value was 50.46 kPa, 156.28% higher than that from three-layer models (19.74 kPa). The proposed segmentation technique may have wide applications in vulnerable plaque research.

Detection of myocardial bridge by optical coherence tomography

Myocardial bridge (MB) is less commonly documented by angiography than autopsy. Optical coherence tomography (OCT) may be useful to detect angiographically undetectable MB. To investigate OCT characteristics of MB, 86 LAD vessels were imaged by OCT. MB was defined as presence of intermediate optical intensity, "fine" layer surrounding coronary artery by OCT. Frequency and characteristics of the angio-detectable and angio-undetectable but OCT-detectable MB were investigated. In a subset of patients with angio-detectable MB, cyclic changes in coronary arterial dimensions were analyzed. OCT detected MB in 44 of 86 (51%). Arc of the MB was significantly larger (334.8 ± 58.5° vs. 268.4 ± 92.1°, P = 0.008) and length was significantly longer (22.6 ± 11.7 mm vs. 14.5 ± 8.1 mm, P = 0.014) in angio-detectable MB than OCT-detectable but angio-undetectable MB. Both vessel (6.8 ± 1.5 to 5.3 ± 1.0 mm2, P = 0.035) and lumen area (4.4 ± 1.5 to 3.1 ± 0.7 mm2, P = 0.040) decreased significantly from diastole to systole. Adventitial (0.08 ± 0.03 to 0.08 ± 0.02 mm, P = 0.828) and intima + plaque thickness (0.12 ± 0.05 to 0.10 ± 0.03 mm, P = 0.398) did not change significantly during cardiac cycle. On the other hand, medial thickness increased significantly from diastole to systole (0.08 ± 0.03 to 0.12 ± 0.03 mm, P = 0.022). In conclusion, MB is frequently detected as intermediate intensity, fine layer by OCT. During systole, vessel and lumen size decrease with increased medial thickness. Therefore, we should be careful for OCT interpretation of the coronary arteries with MB.

Incidence and prognostic impact of the calcified nodule in coronary artery disease patients with end-stage renal disease on dialysis

Coronary artery calcification is frequently observed in coronary artery disease (CAD) patients with end-stage renal disease (ESRD). Calcified nodule (CN) is recognized as one of the vulnerable plaque characteristics responsible for acute coronary syndrome (ACS). Although CN is a cause of ACS in only 10%, its prevalence may be higher in elderly patients and/or ESRD. The aim of this study is to investigate incidence, clinical characteristics, and prognostic impact of CN in CAD patients with ESRD on dialysis. A total of 51 vessels from 49 CAD patients with ESRD on dialysis were enrolled in this study. CN was defined as a high-backscattering mass protruding into the lumen with a strong signal attenuation and an irregular surface by optical coherence tomography. Incidence, clinical characteristics and prognosis of patients with CN were studied. Major adverse cardiac events (MACE) were defined as a composite of all-cause death, non-fatal myocardial infarction, target vessel revascularization (TVR) and stroke. CNs were observed in 30 vessels from 29 patients (59.2%). Duration of dialysis was significantly longer in CN group than in non-CN group (P = 0.03). Overall, all-cause death, cardiac death, TVR and MACE occurred in 7 (14.3%), 3 (6.1%), 11 (22.4%) and 16 (32.7%) patients during follow-up (median 826 days), respectively. Kaplan-Meier survival analysis revealed that MACE-free survival was significantly lower in patients with CN compared with those without CN (Log-rank, P = 0.036).In conclusion, CN was observed in about 60% of the CAD patients with ESRD and was associated with duration of dialysis and worse prognosis.

Incidence and characteristics of incomplete stent apposition in calcified lesions: An optical coherence tomography study

BACKGROUND

Persistent or late acquired incomplete stent apposition (ISA) may be associated with late or very late stent thrombosis following drug-eluting stent implantation. Presence of calcium at the target lesion may increase the risk of ISA even after rotational atherectomy (RA) followed by stenting with high pressure balloon inflation. The aim of this study is to examine the incidence and characteristics of ISA in heavily calcified lesions.

METHODS

A total of 52 heavily calcified coronary artery lesions requiring RA plus stenting were selected and studied. After successful ablation followed by stent implantation, optical coherence tomography (OCT) was performed to assess stent expansion and apposition. Presence or absence of ISA was examined and maximal stent strut to vessel wall distance (max SV distance) was measured. In lesions with repeated OCT at follow-up, serial changes in ISA were investigated.

RESULTS

ISA was documented in 51 of 52 (98%) lesions. Mean max SV distance was 713 ± 371 μm. In lesions with serial OCT images (n = 11), max SV distance decreased significantly (692.1 ± 420.2 to 462.5 ± 387.0 μm, P < 0.01) but persisted in all but 2 lesions (82%).

CONCLUSIONS

ISA is frequently documented in heavily calcified lesions requiring RA. Significant ISA still persisted with minimal improvement in SV distance at follow-up. Prognostic impact of the persistent ISA in such calcified lesions needs further investigations.

Optical coherence tomography's current clinical medical and dental applications: a review

Optical coherence tomography (OCT) is a non-invasive investigative technique that is used to obtain high-resolution three-dimensional (3D) images of biological structures. This method is useful in diagnosing diseases of specific organs like the eye, where a direct biopsy cannot be conducted. Since its inception, significant advancements have been made in its technology. Apart from its initial application in ophthalmology for retinal imaging, substantial technological innovations in OCT brought by the research community have enabled its utilization beyond its original scope and allowed its application in many new clinical areas. This review presents a summary of the clinical applications of OCT in the field of medicine (ophthalmology, cardiology, otology, and dermatology) and dentistry (tissue imaging, detection of caries, analysis of dental polymer composite restorations, imaging of root canals, and diagnosis of oral cancer). In addition, potential advantages and disadvantages of OCT are also discussed.