Virtual Histology and Color Flow Intravascular Ultrasound in Peripheral Interventions

Intravascular Ultrasound in the Endovascular Treatment of Patients With Peripheral Arterial Disease: Current Role and Future Perspectives

Over the last decade, intravascular ultrasound (IVUS) has emerged as a useful adjunctive tool to angiography in an increasing number of catheter-based procedures for peripheral arterial disease (PAD). IVUS catheters offer accurate cross-sectional imaging of arterial vessels with high dimensional accuracy and provide accurate information about lesion morphology. IVUS enables assessment of the plaque morphology, vessel diameter, and the presence of arterial dissections. Furthermore, IVUS is able to properly guide the best choice of appropriate percutaneous transluminal angioplasty (PTA) technique, guide the delivery of different devices, and assess the immediate result of any endovascular intervention. In the present review, the role of IVUS for PAD will be discussed, specifically the applications of IVUS technology during interventional procedures including PTA, stent sizing, crossing total occlusion, assessing residual narrowing and stent apposition and expansion, and atherectomy. Future perspectives of IVUS-guided treatments and cost-effectiveness of the systematic use of IVUS during endovascular interventions will be also discussed.

Safety and efficacy of intravascular ultrasound as an adjunct to stenting for cerebral venous sinus stenosis-induced idiopathic intracranial hypertension: a pilot study

OBJECTIVE

Symptomatic intracranial hypertension can be caused by cerebral venous sinus stenosis (CVSS) and cerebral venous sinus thrombotic (CVST) stenosis, which is usually found in some patients with idiopathic intracranial hypertension (IIH). Recently, at the authors' center, they utilized intravascular ultrasound (IVUS) as an adjunct to conventional venoplasty or stenting to facilitate diagnosis and accurate stent placement in CVSS.

METHODS

The authors designed a retrospective review of their prospective database of patients who underwent IVUS-guided venous sinus stenting between April 2016 and February 2017. Clinical, radiological, and ophthalmological information was recorded and analyzed. IVUS was performed in 12 patients with IIH (9 with nonthrombotic CVSS, 3 with secondary stenosis combined with CVST) during venoplasty through venous access. The IVUS catheter was used from a proximal location to the site of stenosis. Post-stenting follow-up, including symptomatic improvement, stent patency, and adjacent-site stenosis, was assessed at 1 year.

RESULTS

Thirteen stenotic cerebral sinuses in 12 patients were corrected using IVUS-guided stenting. No technical or neurological complications were encountered. The IVUS images were excellent for the diagnosis of the stenosis, and intraluminal thrombi were clearly visualized by using IVUS in 3 (25%) of the 12 patients. A giant arachnoid granulation was demonstrated in 1 (8.3%) of the 12 patients. Intravenous compartments or septations (2 of 12, 16.7%) and vessel wall thickening (6 of 12, 50%) were also noted. At 1-year follow-up, 10 of 12 patients were clinically symptom-free in our series.

CONCLUSIONS

IVUS is a promising tool with the potential to improve the diagnostic accuracy in IIH, aiding in identification of the types of intracranial venous stenosis, assisting in stent selection, and guiding stent placement. Further study of the utility of IVUS in venous stenting and venous stenosis pathology is warranted.

Comparison of plaque morphology between peripheral and coronary artery disease (from the CLARITY and ADAPT-DES IVUS substudies)

OBJECTIVE

The aim of this study was to help understand the different outcomes when treating peripheral arterial disease (PAD) versus coronary artery disease (CAD). We compared plaque morphology between PAD and CAD using intravascular ultrasound.

METHODS

Complete Lesion Assessment with ffR and IVUS TechnologY (CLARITY) was a prospective, multicenter trial that enrolled 50 PAD patients with a lower extremity wound fed by a tibial or a peroneal artery with diameter stenosis more than 50%. Assessment of Dual AntiPlatelet Therapy With Drug Eluting Stents (ADAPT-DES) was a prospective, multicenter, registry that enrolled 8582 CAD patients. We compared preintervention intravascular ultrasound findings in 42 PAD lesions from CLARITY versus 79 matched CAD lesions from ADAPT-DES.

RESULTS

Compared with CAD lesions, PAD lesions had (i) smaller mean vessel, plaque, and lumen volumes; (ii) twice the lesion length; (iii) greater maximum superficial calcium arc and plaque eccentricity (i.e. there was more concentric plaque) measured at the minimum lumen area site; (iv) calcium arc and plaque eccentricity were positively correlated to plaque burden in both PAD and CAD lesions; and (v) calcium arc and the presence of concentric plaque were greater in PAD compared with CAD independent of the degree of plaque burden.

CONCLUSION

Compared with CAD lesions, PAD lesions in a tibial or a peroneal artery were longer; had more concentric, diffuse, and calcified plaque; and had smaller vessel volumes.

Intravascular Ultrasound Characterization of a Tissue-Engineered Vascular Graft in an Ovine Model

Patients who undergo implantation of a tissue-engineered vascular graft (TEVG) for congenital cardiac anomalies are monitored with echocardiography, followed by magnetic resonance imaging or angiography when indicated. While these methods provide data regarding the lumen, minimal information regarding neotissue formation is obtained. Intravascular ultrasound (IVUS) has previously been used in a variety of conditions to evaluate the vessel wall. The purpose of this study was to evaluate the utility of IVUS for evaluation of TEVGs in our ovine model. Eight sheep underwent implantation of TEVGs either unseeded or seeded with bone marrow-derived mononuclear cells. Angiography, IVUS, and histology were directly compared. Endothelium, tunica media, and graft were identifiable on IVUS and histology at multiple time points. There was strong agreement between IVUS and angiography for evaluation of luminal diameter. IVUS offers a valuable tool to evaluate the changes within TEVGs, and clinical translation of this application is warranted.

Usefulness of intraopertive ultrasonography during directional atherectomy using SilverHawk/TurboHawk system

PURPOSE

Directional atherectomy (DA) was introduced for the management of infrainguinal arterial stenosis or occlusive lesions. The procedure success rate in the DEFINITIVE LE study was determined using radiologic imaging. The aim of our study was to determine the usefulness of intraoperative ultrasonography (USG) during DA for evaluating the early results of this procedure.

METHODS

Patients who underwent DA from January to December 2014 were reviewed retrospectively. Twenty lesions from 14 patients with femoral artery stenosis (>70% stenosis) with short segment occlusive lesions (<2 cm in length) were treated. Among 20 lesions, 3 were treated with the TurboHawk system with a protective device due to lesion calcification. The percentage of stenosis during and after DA was determined with USG.

RESULTS

Median follow-up was 5.1 months, and the procedural success rate (<30% stenosis at the end of the procedure) was 100% on angiography, but only 30% on intraoperative USG. On USG, median residual stenosis was 40% (range, 28%-42%) at the end of DA, 40% (range, 30%-55%) at 1 month, 55% (range, 35%-85%) at 6 months, and 64% (range, 60%-100%) at 1 year. There was one dissection, but no cases of perforation, pseudoaneurysm, or thrombosis. Primary patency, which was defined as a peak systolic velocity ratio ≤3.5 with no reintervention at 6 months, was found in 18 lesions (90%), and 11 of 14 patients (78.6%) were free of ischemic symptoms such as claudication at 6 months.

CONCLUSION

Our results demonstrated that DA with intraoperative USG is an effective treatment option for short segment occlusive lesions of the femoral artery.

Virtual Histology Intravascular Ultrasound in Carotid Interventions

Purpose:

To report early clinical experience with virtual histology intravascular ultrasound (VH IVUS) in carotid endoluminal repair.

Technique:

A 2.9-F, 20-MHz catheter that utilizes computer software to demonstrate the histological components of arteriosclerotic plaque was evaluated during carotid angioplasty and stenting. VH IVUS images were created following a pullback through the carotid stenosis and produced a color-coded map of the different histological constituents of the disease (dark green: fibrous, yellow/green: fibrofatty, white: calcified, and red: necrotic lipid core plaque).

Conclusion:

VH IVUS produces a color-coded map of the different histological components of artery plaque. It has the potential to predict how the plaque is likely to behave at the moment of endoluminal treatment.

Invasive evaluation of plaque morphology of symptomatic superficial femoral artery stenoses using combined near-infrared spectroscopy and intravascular ultrasound

The purpose of this study is to characterize the plaque morphology of severe stenoses in the superficial femoral artery (SFA) employing combined near-infrared spectroscopy and intravascular ultrasound (NIRS-IVUS). Atherosclerosis is the most common cause of symptomatic peripheral arterial disease. Plaque composition of SFA stenoses has been characterized as primarily fibrous or fibrocalcific by non-invasive and autopsy studies. NIRS has been validated to detect lipid-core plaque (LCP) in the coronary circulation. We imaged severe SFA stenoses with NIRS-IVUS prior to revascularization in 31 patients (46 stenoses) with Rutherford claudication ⩾ class 3. Angiographic parameters included lesion location and stenosis severity. IVUS parameters included plaque burden and presence of calcium. NIRS images were analyzed for LCP and maximum lipid-core burden index in a 4-mm length of artery (maxLCBI4mm). By angiography, 38 (82.6%) lesions were calcified and 9 (19.6%) were chronic total occlusions. Baseline stenosis severity and lesion length were 86.0 ± 11.0% and 36.5 ± 46.5 mm, respectively. NIRS-IVUS identified calcium in 45 (97.8%) lesions and LCP in 17 (37.0%) lesions. MaxLCBI4mm was 433 ± 244. All lesions with LCP also contained calcium; there were no non-calcified lesions with LCP. In conclusion, this is the first study of combined NIRS-IVUS in patients with PAD. NIRS-IVUS demonstrates that nearly all patients with symptomatic severe SFA disease have fibrocalcific plaque, and one-third of such lesions contain LCP. These findings contrast with those in patients with acute coronary syndromes, and may have implications regarding the pathophysiology of atherosclerosis in different vascular beds.

Effect of Intravascular Ultrasound-assisted Thoracic Endovascular Aortic Repair for "Complicated" Type B Aortic Dissection

Background:

Intravascular ultrasound (IVUS) examination can provide useful information during endovascular stent graft repair. However, its actual clinical utility in thoracic endovascular aortic repair (TEVAR) for type B aortic dissection (type B-AD) remains unclear, especially in complicated aortic dissection. We evaluated the effect of IVUS as a complementary tool during TEVAR.

Methods:

From September 2011 to April 2012, we conducted a prospective cohort study of 47 consecutive patients with “complicated” type B-AD diagnosed. We divided the patients into two groups: IVUS-assisted TEVAR group and TEVAR using angiography alone group. The general procedure of TEVAR was performed. We evaluated the perioperative and follow-up events. Patient demographics, comorbidities, preoperative images, dissection morphology, details of operative strategy, intraoperative events, and postoperative course were recorded.

Results:

A total of 47 patients receiving TEVAR were enrolled. Among them (females, 8.51%; mean age, 57.38 ± 13.02 years), 13 cases (27.66%) were selected in the IVUS-assisted TEVAR group, and 34 were selected in the TEVAR group. All patients were symptomatic. The average diameter values of IVUS measurements in the landing zone were greater than those estimated by computed tomography angiography (31.82 ± 4.21 mm vs. 30.64 ± 4.13 mm, P < 0.001). The technique success rate was 100%. Among the postoperative outcomes, statistical differences were only observed between the IVUS-assisted TEVAR group and TEVAR group for total operative time and the amount of contrast used (P = 0.013 and P < 0.001, respectively). The follow-up ranged from 15 to 36 months for the IVUS-assisted TEVAR group and from 10 to 35 months for the TEVAR group (P = 0.646). The primary endpoints were no statistical difference in the two groups.

Conclusions:

Intraoperative IVUS-assisted TEVAR is clinically feasible and safe. For the endovascular repair of “complicated” type B-AD, IVUS may be helpful for understanding dissection morphology and decrease the operative time and the amount of contrast used.

Utility of intravascular ultrasound in intracranial and extracranial neurointerventions: experience at University at Buffalo Neurosurgery-Millard Fillmore Gates Circle Hospital

Intravascular ultrasound (IVUS) generates high-resolution cross-sectional images and sagittal reconstructions of the vessel wall and lumen. As a result, this imaging modality can provide accurate measurements of the degree of vessel stenosis, allow the detection of intraluminal thrombus, and analyze the plaque composition. The IVUS modality is widely used in interventional cardiology, and its use in neurointerventions has gradually increased. With case examples, the authors illustrate the utility of IVUS as an adjunct to conventional angiography for a wide range of intracranial and extracranial neurointerventions.

Intravascular ultrasound: principles and cerebrovascular applications

Intravascular sonography is a valuable tool for the morphologic assessment of coronary atherosclerosis and the effect of pharmacologic and nonpharmacologic interventions on the progression or stabilization of atherosclerosis. An analysis of the different modes, applications, and limitations is provided on the basis of review of existing data from multiple clinical case studies, trials, and mechanistic studies. Intravascular sonography has been used to assess the outcomes of different percutaneous interventions, including angioplasty and stent implantation, and to provide detailed characterization of atherosclerotic lesions, aneurysms, and dissections within the cerebrovascular circulation. Evolution of intravascular sonographic technology has led to the development of more sophisticated diagnostic tools such as color-flow, virtual histology, and integrated backscatter intravascular sonography. The technologic advancement in intravascular sonography has the potential of providing more accurate information prior, during, and after a medical or endovascular intervention. Continued assessment of this diagnostic technique in both the intracranial and extracranial circulation will lead to increased use in clinical practice with the intent to improve outcomes.

Imaging in endovascular therapy: our future

The endovascular therapist now has many modern imaging techniques available to plan and execute treatment, whereas in the past vascular surgeons relied mostly on clinical examination and arteriography. Advances in computer technology have enabled fast acquisition and processing of the large amounts of digital data essential to capture the dynamic information from fast-flowing blood at high resolution. Functional imaging has begun to play a role in predicting stability of progressive vascular disease and the need for and risks of intervention. Computing power now affords the interventionist the ability to handle imaging data in powerful 3-dimensional programs and electronically "in-lay" a variety of devices to plan complex endovascular procedures from the familiar platform of a laptop. In four major clinical areas, carotid intervention, peripheral intervention, endoluminal grafting, and cardiac imaging, we review the latest advances and changes with an eye toward how we should best be using imaging in our patients undergoing endovascular treatment...now and into the future.

Virtual histology intravascular ultrasound assessment of carotid artery disease: the Carotid Artery Plaque Virtual Histology Evaluation (CAPITAL) study

PURPOSE

To determine the diagnostic accuracy of virtual histology intravascular ultrasound imaging (VH IVUS) of carotid plaque and to assess the feasibility of VH IVUS to identify plaque with embolic potential in patients undergoing carotid artery stenting (CAS).

METHODS

Thirty patients (17 men; mean age 74+/-7 years) were entered nonrandomly into a single-center, prospective, 2-arm study following FDA and Institutional Review Board approval. In one arm, 15 patients underwent VH IVUS examination of carotid plaque with a cerebral protection device immediately followed by carotid endarterectomy (CEA). A comparison of "virtual" with true histology was then performed, classifying plaque type by VH IVUS and histopathology in a blinded study. In the second arm, 15 patients undergoing CAS had a preliminary VH IVUS scan performed with cerebral protection. Debris collected from the filter following stenting was examined histologically and compared with the VH IVUS data.

RESULTS

The diagnostic accuracy of VH IVUS to agree with true histology in different carotid plaque types was 99.4% in thin-cap fibroatheroma, 96.1% for calcified thin-cap fibroatheroma, 85.9% in fibroatheroma, 85.5% for fibrocalcific, 83.4% in pathological intimal thickening, and 72.4% for calcified fibroatheroma. Filter debris was captured in 2 patients prior to CEA and in 4 patients undergoing CAS for restenosis; VH IVUS classification of plaque composition was consistent with the histological evaluation of filter fragments. Calcified nodules projecting into the carotid artery lumen were associated with a higher incidence of previous neurological symptoms (66.7% versus 33.3%, p<0.05), while patients on aspirin has significantly less necrotic lipid core plaque detected by VH IVUS than patients not taking aspirin (6.4%+/-4.7% versus 9.7%+/-2.8%, p<0.05).

CONCLUSION

This study showed a strong correlation between VH IVUS plaque characterization and the true histological examination of the plaque following endarterectomy, particularly in "vulnerable" plaque types. The feasibility study to examine VH IVUS data and the filter debris histology in CAS patients supports a larger prospective study.