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

Intravascular ultrasound and virtual histology of basilar artery atherosclerotic lesion. A case report

To our knowledge, this paper presents the first intravascular ultrasound and virtual histology (IVUS-VH) study in the basilar artery. IVUS-VH serves to characterize and determine the extension of the plaque and we also to check stent placement.

The association between renal atherosclerotic plaque characteristics and renal function before and after renal artery intervention

OBJECTIVE

To evaluate the effect of plaque composition on renal function after renal artery intervention (RAI).

PATIENTS AND METHODS

In 33 consecutive patients with atherosclerotic renal artery stenosis (enrolled between January 1, 2007, and April 30, 2009), renal angiography, pressure gradients across the lesion, and intravascular ultrasonography (IVUS) with virtual histology (VH)-derived plaque characteristics were assessed. In 25 patients who underwent RAI, estimated glomerular filtration rate (eGFR) was evaluated at baseline and at 3 months.

RESULTS

Mean pressure gradients across the lesion were poorly associated with baseline eGFR (r=-0.37; P=.07). In gray scale IVUS data, only remodeling index was significantly correlated with baseline eGFR (r=-0.38; P=.03). Plaque components classified by VH-IVUS had no correlation with baseline eGFR. During follow-up of 25 patients, the improvement in eGFR after RAI was observed in 9 patients, unchanged in 3, and deteriorated in 13. Overall, follow-up eGFR (median, 49.0 mL/min/1.73 m(2); interquartile range [IQR], 40.6-63.9 mL/min/1.73 m(2)) was unchanged compared with baseline eGFR (median, 53.8 mL/min/1.73 m(2); IQR, 41.4-63.4 mL/min/1.73 m(2); P=.38). The percent change in eGFR (median, -0.2%; IQR, -16.0% to 16.0%) after RAI had a significant negative correlation with the mean percentage of necrotic core classified by VH-IVUS (r=-0.47; P=.02), and the mean percentage of necrotic core was significantly larger in patients with deterioration of eGFR than in patients without deterioration of eGFR (median, 12.7%; IQR, 9.5%-19.5%; vs median, 8.3%; IQR, 5.5%-11.6%; P=.04).

CONCLUSION

In patients with atherosclerotic renal artery stenosis, the change in eGFR after RAI was related to plaque composition classified by VH-IVUS. The evaluation of plaque composition may provide more insights into the change in renal function after RAI.

Reproducibility of IVUS border detection for carotid atherosclerotic plaque assessment

Plaque composition is a potentially important diagnostic feature for carotid artery stenting (CAS). The purpose of this investigation is to evaluate the reproducibility of manual border correction in intravascular ultrasound with virtual histology (VH IVUS) images. Three images each were obtained from 51 CAS datasets on which automatic border detection was corrected manually by two trained observers. Plaque was classified using the definitions from the CAPITAL (Carotid Artery Plaque Virtual Histology Evaluation) study, listed in order from least to most pathological: no plaque, pathological intimal thickening, fibroatheroma, fibrocalcific, calcified fibroatheroma, thin-cap fibroatheroma, and calcified thin-cap fibroatheroma. Inter-observer variability was quantified using both weighted and unweighted Kappa statistics. Bland-Altman analysis was used to compare the cross-sectional areas of the vessel and lumen. Agreement using necrotic core percentage as the criterion was evaluated using the unweighted Kappa statistic. Agreement between classifications of plaque type was evaluated using the weighted Kappa statistic. There was substantial agreement between the observers based on necrotic core percentage (κ=0.63), while the agreement was moderate (κ(quadratic)=0.60) based on plaque classification. Due to the time-consuming nature of manual border detection, an improved automatic border detection algorithm is necessary for using VH IVUS as a diagnostic tool for assessing the suitability of patients with carotid artery occlusive disease for CAS.

Evaluation of plaque composition by intravascular ultrasound "virtual histology": the impact of dense calcium on the measurement of necrotic tissue

AIMS

We aimed to evaluate if the co-localisation of calcium and necrosis in intravascular ultrasound virtual histology (IVUS-VH) is due to artefact, and whether this effect can be mathematically estimated.

METHODS AND RESULTS

We hypothesised that, in case calcium induces an artefactual coding of necrosis, any addition in calcium content would generate an artificial increment in the necrotic tissue. Stent struts were used to simulate the "added calcium". The change in the amount and in the spatial localisation of necrotic tissue was evaluated before and after stenting (n=17 coronary lesions) by means of a especially developed imaging software. The area of "calcium" increased from a median of 0.04 mm2 at baseline to 0.76 mm2 after stenting (p<0.01). In parallel the median necrotic content increased from 0.19 mm2 to 0.59 mm2 (p<0.01). The "added" calcium strongly predicted a proportional increase in necrosis-coded tissue in the areas surrounding the calcium-like spots (model R2=0.70; p<0.001).

CONCLUSIONS

Artificial addition of calcium-like elements to the atherosclerotic plaque led to an increase in necrotic tissue in virtual histology that is probably artefactual. The overestimation of necrotic tissue by calcium strictly followed a linear pattern, indicating that it may be amenable to mathematical correction.

Intraarterial ultrasound in pancreatic cancer: feasibility study and preliminary results

Despite technological advances in computed tomography (CT) and magnetic resonance imaging, the involvement of the celiac or mesenteric artery in pancreatic cancer remains uncertain in many cases. Infiltration of these vessels is important in making decisions about therapy choices but often can only be definitively determined through laparotomy. Local (intraarterial) ultrasound may increase diagnostic accuracy. Using the Volcano intravascular ultrasound (IVUS) system, we applied a transfemoral method to scan the celiac and mesenteric arteries directly intraarterial. This technique was used in five patients with suspected pancreatic cancer. Technical success was achieved in all cases. In one case, a short dissection of the mesenteric artery occurred but could be managed interventionally. In tumors that did not contact with the vessels, IVUS was unable to display the tissue pathology. Our main interest was the infiltration of the arteries. In one case, infiltration was certain in the CT scan but uncertain in two patients. In the latter two cases, IVUS correctly predicted infiltration in one and freedom from tumor in the other case. In our preliminary study, IVUS correctly predicted arterial infiltration in all cases. IVUS did not provide new information when the tumor was far away from the vessel. Compared with IVUS in the portal vein, the information about the artery is more detailed, and the vessel approach is easier. These results encouraged us to design a prospective study to evaluate the sensitivity and specificity of this method.

Combined optical coherence tomography and intravascular ultrasound radio frequency data analysis for plaque characterization. Classification accuracy of human coronary plaques in vitro

This study was performed to characterize coronary plaque types by optical coherence tomography (OCT) and intravascular ultrasound (IVUS) radiofrequency (RF) data analysis, and to investigate the possibility of error reduction by combining these techniques. Intracoronary imaging methods have greatly enhanced the diagnostic capabilities for the detection of high-risk atherosclerotic plaques. IVUS RF data analysis and OCT are two techniques focusing on plaque morphology and composition. Regions of interest were selected and imaged with OCT and IVUS in 50 sections, from 14 human coronary arteries, sectioned post-mortem from 14 hearts of patients dying of non-cardiovascular causes. Plaques were classified based on IVUS RF data analysis (VH-IVUS^TM), OCT and the combination of those. Histology was the benchmark. Imaging with both modalities and coregistered histology was successful in 36 sections. OCT correctly classified 24; VH-IVUS 25, and VH-IVUS/OCT combined, 27 out of 36 cross-sections. Systematic misclassifications in OCT were intimal thickening classified as fibroatheroma in 8 cross-sections. Misclassifications in VH-IVUS were mainly fibroatheroma as intimal thickening in 5 cross-sections. Typical image artifacts were found to affect the interpretation of OCT data, misclassifying intimal thickening as fibroatheroma or thin-cap fibroatheroma. Adding VH-IVUS to OCT reduced the error rate in this study.

Research priorities for intracranial atherosclerotic diseases

The current review summarizes the characteristics of existing experimental models for intracranial atherosclerosis in rabbits, pigs, and dogs with potential implications for research. New methodologies for understanding plaque morphology, and plaque quantitation and its prognostic implications are important for risk stratification in regards to ischemic events and lesion progression. A potential treatment strategy for intracranial atherosclerotic disease may be aimed at medical therapies that induce plaque regression. The treatment with statins to stabilize and/or promote plaque regression of intracranial atherosclerotic lesions is largely inferred from data in the coronary literature. In patients with multisegmented intracranial atherosclerotic diseases with no other therapeutic option, angiogenic growth factors may represent a new venue.

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.

Intracranial atherosclerotic disease: an update

The consensus conference on intracranial atherosclerosis provides a comprehensive review of the existing literature relevant to the epidemiology, diagnosis, prevention, and treatment of intracranial atherosclerosis, and identifies principles of management and research priorities. Patients who have suffered a stroke or transient ischemic attack attributed to stenosis (50-99%) of a major intracranial artery face a 12 to 14% risk for subsequent stroke during the 2-year period after the initial ischemic event, despite treatment with antithrombotic medications. The annual risk for subsequent stroke may exceed 20% in high-risk groups. In patients with intracranial atherosclerotic disease, short-term and long-term anticoagulation is not superior to antiplatelet treatment. Overall, the subgroup analyses from randomized trials provide evidence about benefit of aggressive atherogenic risk factor management. Intracranial angioplasty with or without stent placement has evolved as a therapeutic option for patients with symptomatic intracranial atherosclerotic disease, particularly those with high-grade stenosis with recurrent ischemic symptoms, medication failure, or both. A multicenter randomized trial is currently under way to compare stent placement with intense medical management for patients with high-grade symptomatic intracranial atherosclerotic disease.

Evaluation of peripheral atherosclerosis: a comparative analysis of angiography and intravascular ultrasound imaging

OBJECTIVE

Angiography remains a critical component for diagnostic imaging and therapeutic intervention in peripheral arterial disease (PAD). The goal of this study was to compare angiography with corresponding intravascular ultrasound (IVUS) imaging of the same vessels in patients with PAD.

METHODS

From 2004 to 2008, 93 patients undergoing angiography for PAD were recruited in a prospective observational analysis. At the time of angiography, diseased lower extremities were interrogated using a 10-cm IVUS pullback with registration points. IVUS data were analyzed with radiofrequency techniques for vessel and lumen diameter, plaque volume, plaque composition, and cross-sectional area. Similarly, three vascular surgeons blinded to the IVUS data graded corresponding angiographic images according to vessel diameter, degree of stenosis, degree of calcification, and extent of eccentricity. Statistical analyses of matched IVUS images and angiograms were performed.

RESULTS

The distribution of demographic and risk variables were typical for PAD: 54% male, 96% hypertension, 78% hyperlipidemia, 44% diabetic, 87% tobacco history, 65% coronary artery disease, and 10% end-stage renal disease. Symptoms precipitating the angiographic evaluation included claudication (53%), rest pain (18%), and tissue loss (29%). Angiographic and IVUS interpretation were similar for luminal diameters, but external vessel diameter was greater by IVUS imaging (7.0 +/- 0.7 vs 5.2 +/- 0.8 mm, P < .05). The two-dimensional diameter method resulted in a significant correlation for stenosis determination (r = 0.84); however, IVUS determination of vessel area stenosis was greater by 10% (95% confidence interval, 0.3%-21%, P < .05). IVUS imaging indicated that a higher proportion of plaques were concentric. Grading of calcification was moderate to severe in 40% by angiography but in only 7% by IVUS (P < .05).

CONCLUSIONS

In the evaluation of PAD, angiography and IVUS imaging provide similar luminal diameters and diameter-reducing stenosis measurements. Determination of overall vessel diameter and interpretation of plaque morphology by angiography are discordant from IVUS-derived data.

How to avoid complications associated with carotid angioplasty and stenting

Carotid angioplasty and stenting (CAS) has been proposed as an alternative to surgery and is now performed more frequently and is well accepted, at least for high surgical risk patients. However, complications and particularly embolic strokes, even with a meticulous technique, can occur at any step of the procedure. Silent embolism is detected after CAS and may be a problem that needs to be discussed. To avoid and reduce these complications associated with CAS, it is important to have good indications dependent upon on good patient and lesions selection, as well as correct technique. New parameters have been proposed, particularly for asymptomatic lesions. The authors consider that embolic protection devices (EPDs) are mandatory for CAS, and new techniques will be presented. The choice of the EPD depends on the clinical status of the patient, the lesion morphology and characteristics, and the anatomy of the artery. All stents are not equivalent and so a good choice of the stent is necessary to avoid and reduce the complications associated with CAS, and experienced operators are also needed. With all these considerations, CAS can now be performed with acceptable outcomes and in certain population the results are comparable or superior to surgery. The results of ongoing randomized trials are awaited.

Virtual histology-intravascular ultrasound in assessment of carotid plaques: ex vivo study

OBJECTIVE

Virtual histology-intravascular ultrasound (VH-IVUS) has been reported to be useful in detecting the components of coronary plaques in vivo. Recently, the application of VH-IVUS to peripheral interventions has been evaluated. The aim of this study was to examine the extent to which the necrotic core of carotid plaques could be assessed accurately by VH-IVUS compared with histopathology.

METHODS

A total of 37 carotid plaques underwent ex vivo VH-IVUS within 24 hours after endarterectomy. Ninety-five segments of virtual histological images were matched to histological sections. The area of the necrotic core on histological sections was compared with that on virtual histological images. Intraplaque hemorrhage (IPH) was histopathologically graded by its severity using immunohistochemical staining for glycophorin A as a marker. The relationship of the severity of the IPH to the necrotic core was histopathologically evaluated. The correlation between the necrotic core or IPH with symptomatology was also evaluated.

RESULTS

The area of the necrotic core on virtual histological images (median, 8.0%; interquartile range, 5.0%-13%) was significantly smaller compared with that of the histological sections (median, 50%; interquartile range, 40%-63%) (P < 0.0001). The Bland-Altman analysis showed poor agreement in the necrotic core measurement between virtual histological images and histological sections (mean difference, 39.8%; 95% confidence interval, 35.8%-43.8%). Severe IPH was significantly associated with a larger necrotic core and symptomatology (P < 0.0001 and P = 0.0039, respectively). The area of necrotic core on the virtual histological analysis did not correlate with symptomatology (P = 0.70), but that on pathological analysis tended to correlate with symptomatology (P = 0.059).

CONCLUSION

In the present virtual histological algorithm, the underestimation of the necrotic core was revealed. The lack of a hemorrhage component in the virtual histological algorithm is a leading cause of its underestimation.

Validation of in vivo plaque characterisation by virtual histology in a rabbit model of atherosclerosis

AIMS

Most acute coronary syndromes are caused by plaque rupture. The risk of plaque rupture is related to plaque composition. The purpose of this study was to validate VH-IVUS for in vivo plaque characterisation.

METHODS AND RESULTS

Six rabbits were fed a cholesterol-supplemented diet for 12 to 18 months. Thereafter, VH-IVUS imaging of the aorta was performed. After sacrifice, the VH-IVUS images were matched to the corresponding histological cross sections. A total of 260 atherosclerotic plaques were analysed. VH-IVUS had a high sensitivity, specificity and positive predictive value for the detection of non-calcified thin cap fibroatheroma (88%, 96%, 87%, respectively) and calcified thin cap fibroatheroma (95%, 99%, 93%, respectively). These values were respectively 82%, 94%, 85% for non-calcified fibroatheroma and 78%, 98%, 84% for calcified fibroatheroma. The lowest values were obtained for pathological intimal thickening (74%, 92%, 70%, respectively). For all plaque types, VH-IVUS had a kappa-value of 0.79. Linear regression analysis and Bland-Altman plots showed a strong correlation between VH-IVUS and histology for fibrous tissue, fibrofatty tissue, necrotic calcified tissue and confluent necrotic core.

CONCLUSIONS

VH-IVUS showed a good accuracy for in vivo plaque characterisation and is a promising technique for the detection of the vulnerable plaque.

Association of plaque composition and vessel remodeling in atherosclerotic renal artery stenosis: a comparison with coronary artery disease

OBJECTIVES

The current study was designed to investigate the relationship between renal arterial structure and vessel remodeling in patients with atherosclerotic renal artery stenosis (RAS), compared with that seen in coronary artery disease (CAD).

BACKGROUND

The nature and the tissue characterization of atherosclerotic RAS lesions have not been fully explored.

METHODS

Gray scale and virtual histology (VH) intravascular ultrasound imaging was used to assess 23 lesions in 14 consecutive RAS patients and 20 left main trunk lesions in age-matched CAD patients. Analysis included assessment of vessel area and atherosclerotic plaque area of the main renal artery or left main trunk. Plaque was characterized as fibrous tissue, fibro-fatty tissue, necrotic core, and dense calcium. Remodeling was assessed by means of the remodeling index (RI).

RESULTS

Positive remodeling (defined as RI > or =1.05) was present in 15 RAS and 9 CAD lesions, whereas intermediate/negative remodeling (RI <1.05) was present in 8 RAS and 11 CAD lesions. VH showed that the fibrous tissue was the most prominent plaque composition, followed by fibro-fatty, necrotic core, and dense calcium in both vascular beds. Greater vascular adaptive enlargement was observed in slices with plaque burden < or =40% compared with plaque burden >40% (p < 0.001 for all). Vessel area had a positive association with the area of all VH components (p < 0.001, for all). VH analysis shows that the most powerful determinant of adaptive vessel enlargement is dense calcium in RAS (p < 0.001), while that is necrotic core in CAD (p < 0.001). Necrotic core and dense calcium areas were greater in lesions with positive remodeling compared with intermediate/negative remodeling (p = 0.03, p = 0.03, respectively, in RAS; p = 0.005, p = 0.03, respectively, in CAD).

CONCLUSIONS

The current study demonstrates in humans that plaque composition as assessed by VH intravascular ultrasound has an important role of adaptive vessel enlargement, and it is related to renal artery remodeling in RAS in a pattern similar to CAD.

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.

Segmental coronary endothelial dysfunction in patients with minimal atherosclerosis is associated with necrotic core plaques

BACKGROUND/OBJECTIVE

Endothelial dysfunction and atherosclerosis are systemic disorders, but are often characterised by segmental involvement and complications. A potential mechanism for local involvement early in the disease process may be related to plaque composition. This study was designed to test the hypothesis that in patients with minimal coronary atherosclerosis, coronary artery segments with abnormal endothelial function have specific plaque characteristics.

METHODS

Intravascular ultrasound (IVUS) images were obtained from 30 patients who underwent coronary endothelial function assessment. Spectral analysis of the IVUS radiofrequency data was used for assessment of plaque composition. IVUS findings of the coronary sections were compared according to the corresponding endothelial response to acetylcholine.

RESULTS

Sections with a decrease epicardial coronary arterial diameter in response to acetylcholine had smaller baseline lumen (7.5 (2.4) mm(2) vs 8.8 (3.3) mm(2), p = 0.006) but larger plaque burden (37.1% (9.4%) vs 31% (7%), p = 0.003) than sections with normal endothelial response. Sections with endothelial dysfunction had larger necrotic core plaques: 0.13 (0.03-0.33) mm(2) vs 0.0 (0.0-0.07), p<0.001 and more dense calcium: 0.03 (IQR 0.0-0.13) mm(2) vs 0.0 (0.0-0.10) mm(2), p<0.01), than those with normal endothelial response. Only necrotic core area was associated with endothelial dysfunction (p<0.001) after adjusting for other measures.

CONCLUSIONS

This study suggests that local coronary endothelial dysfunction in patients with minimal coronary atherosclerosis is associated with plaque characteristics that are typical of vulnerable plaques.

Intravascular Ultrasound Analysis of Correlation between Plaque-Morphology and Risk Factors in Peripheral Arterial Disease

OBJECTIVE

To analyze relationships between plaque-morphology classified by intravascular ultrasound (IVUS) and risk factors in patients with peripheral arterial disease (PAD).

METHODS

We performed IVUS in 203 patients with PAD. Multiple regression and logistic analysis were used to assess relationships between plaque-morphology (degree of calcification, presence of a lipid core, intimal flap and thrombus) and risk factors including diabetes mellitus, hypertension, dyslipidemia, estimated glomerular filtration rate (eGFR), HbA1c and the homeostasis model assessment-insulin resistance ratio (HOMA-IR).

RESULTS

IVUS data led to 22% of lesions being classified as soft, 18% as fibrous, 32% as calcified, and 28% as mixed. Calcification was present in the superficial and deep layers in 65% and 35% of cases, respectively, and a lipid core, intimal flap and thrombus were found in 31%, 5.4% and 3.0%, respectively. The calcified angle correlated with HbA1c and eGFR (p < 0.05). Associations were found between deep calcification and HOMA-IR (odds ratio: 4.4, p < 0.05) and a lipid core and hypercholesterolemia (odds ratio: 3.2, p < 0.05). The odds ratio for intimal flap was 15.6 times with hypercholesterolemia (p < 0.05) and 16.9 times with a high HOMA-IR (p < 0.01).

CONCLUSION

Plaque calcification and morphology are associated with chronic kidney disease, insulin resistance and dyslipidemia in PAD patients.

Can periprocedural hypotension in carotid artery stenting be predicted? A carotid morphologic autonomic pathologic scoring model using virtual histology to anticipate hypotension

SUMMARY

Periprocedural hypotension, which frequently occurs during carotid artery stenting (CAS), is an important risk factor for complications such as stroke or death after CAS. To determine if a scoring model can be established to predict periprocedural hypotension (systolic blood pressure < or = 90 mm Hg) and prolonged periprocedural hypotension (requiring vasopressor for > 3 hours) in CAS, we conducted a prospective cohort study of patients undergoing interventional treatment of cervical carotid artery stenosis in an urban tertiary referral hospital from April 2006 to April 2007. Forty-eight stenotic lesions in 45 consecutive patients treated with CAS were included in the study. Multivariate analysis showed three independent risk factors of periprocedural hypotension; "fibrous plaque on Virtual Histology" (P = 0.029), "stenotic lesion involving both the common carotid artery and internal carotid artery on angiogram" (P = 0.004), and "patients without history of diabetes mellitus" (P = 0.020). Further, "distance between carotid bifurcation and point of minimum lumen size < or = 10 mm on angiogram" (P = 0.003) was an independent risk factor of prolonged periprocedural hypotension. Carotid morphologic autonomic pathologic score (carotid MAPS), determined by adding one point for each of those risk factors (total 0 to 4), had good discrimination for both periprocedural hypotension (area under receiver operating characteristic curve: ROC AUC = 0.876; SE 0.053) and prolonged periprocedural hypotension (ROC AUC = 0.811; SE 0.066). Carotid MAPS is useful for predicting periprocedural hypotension and prolonged periprocedural hypotension during CAS.

Intravascular ultrasound of symptomatic intracranial stenosis demonstrates atherosclerotic plaque with intraplaque hemorrhage: a case report

BACKGROUND

Intracranial artery stenosis is assumed to represent atherosclerotic plaque. Catheter cerebral arteriography shows that intracranial stenosis may progress, regress, or remain unchanged. It is counterintuitive that atherosclerotic plaque should spontaneously regress, raising questions about the composition of intracranial stenoses. Little is known about this disease entity in vivo. We provide the first demonstration of in vivo atherosclerotic plaque with intraplaque hemorrhage using intravascular ultrasound (IVUS).

CASE DESCRIPTION

A 35-year-old man with multiple vascular risk factors presented with recurrent stroke failing medical therapy. Imaging demonstrated left internal carotid artery occlusion, severe intracranial right internal carotid artery stenosis, and cerebral perfusion failure. Cerebral arteriography with IVUS confirmed 85% stenosis of the petrous right carotid artery due to atherosclerotic plaque with intraplaque hemorrhage. Intracranial stent-supported angioplasty was performed with IRB approval. The patient recovered without complication.

CONCLUSIONS

This case supports the premise that symptomatic intracranial stenosis can be caused by atherosclerotic plaque complicated by intraplaque hemorrhage similar to coronary artery plaque. IVUS provides additional characteristics that define intracranial atherosclerosis and high-risk features. To our knowledge, this is the first report of stroke due to unstable atherosclerotic plaque with intraplaque hemorrhage in vivo.

Effects of the direct lipoprotein-associated phospholipase A(2) inhibitor darapladib on human coronary atherosclerotic plaque

BACKGROUND

Lipoprotein-associated phospholipase A(2) (Lp-PLA(2)) is expressed abundantly in the necrotic core of coronary lesions, and products of its enzymatic activity may contribute to inflammation and cell death, rendering plaque vulnerable to rupture.

METHODS AND RESULTS

This study compared the effects of 12 months of treatment with darapladib (an oral Lp-PLA(2) inhibitor, 160 mg daily) or placebo on coronary atheroma deformability (intravascular ultrasound palpography) and plasma high-sensitivity C-reactive protein in 330 patients with angiographically documented coronary disease. Secondary end points included changes in necrotic core size (intravascular ultrasound radiofrequency), atheroma size (intravascular ultrasound gray scale), and blood biomarkers.

BACKGROUND

=0.37). In contrast, Lp-PLA(2) activity was inhibited by 59% with darapladib (P<0.001 versus placebo). After 12 months, there were no significant differences between groups in plaque deformability (P=0.22) or plasma high-sensitivity C-reactive protein (P=0.35). In the placebo-treated group, however, necrotic core volume increased significantly (4.5+/-17.9 mm(3); P=0.009), whereas darapladib halted this increase (-0.5+/-13.9 mm(3); P=0.71), resulting in a significant treatment difference of -5.2 mm(3) (P=0.012). These intraplaque compositional changes occurred without a significant treatment difference in total atheroma volume (P=0.95).

CONCLUSIONS

Despite adherence to a high level of standard-of-care treatment, the necrotic core continued to expand among patients receiving placebo. In contrast, Lp-PLA(2) inhibition with darapladib prevented necrotic core expansion, a key determinant of plaque vulnerability. These findings suggest that Lp-PLA(2) inhibition may represent a novel therapeutic approach.

Arterial calcification increases in distal arteries in patients with peripheral arterial disease

The aim of this study was to determine if significant differences in plaque composition exist between the popliteal and tibial vessels in patients with severe peripheral arterial disease (PAD). Forty-four patients with PAD required either above-knee (n = 38), below-knee (n = 5), or through-knee (n = 1) amputation for pedal sepsis/gangrene. The 51 vessels (anterior tibial, n = 9; posterior tibial, n = 10; peroneal, n = 3; popliteal, n = 29) were obtained and underwent intravascular ultrasound (IVUS) evaluation ex vivo within 24 hr of amputation. Sequential IVUS data were obtained at known intervals throughout the vessel length and then analyzed with radiofrequency techniques for quantification of plaque composition, plaque volume, and total vessel volume. Plaque composition was categorized as fibrous, fibro-fatty, necrotic core, and dense calcium. Clinical data were obtained via review of electronic records at the time of amputation. Two-sided t-tests were performed to compare components within each plaque. Results are expressed as mean percentage +/- standard error of the mean. Tibial vessels had more dense calcium within these plaques than popliteal arteries (33.8 +/- 5.6% vs. 10.6 +/- 1.9%, p < 0.001). Consequently, distal vessels had less fibro-fatty and fibrous plaque than popliteal arteries (7.7 +/- 1.4% vs. 13.1 +/- 1.2%, p < 0.005; 42.4 +/- 4.7% vs. 61.4 +/- 2.2%, p < 0.001, respectively). Necrotic core plaque composition was found to be similar when comparing tibial versus popliteal arteries (16.1% vs. 14.9%, p = nonsignificant). Clinical factors including diabetes, hyperlipidemia, and chronic renal insufficiency were not associated with plaque composition differences using a univariate analysis. As we progress distally in the arterial tree of patients with PAD, calcium plaque content increases with decreasing burden of fibro-fatty plaque. Clinical and demographic factors, with the exception of smoking, were not found to be associated with atherosclerotic plaque composition.

Technology insight: in vivo coronary plaque classification by intravascular ultrasonography radiofrequency analysis

Acute coronary syndromes or sudden coronary death are often the first manifestations of coronary artery disease. In the majority of patients, acute coronary syndrome events are caused by plaque rupture in flow-limiting and non-flow-limiting angiographically intermediate stenoses. Histopathologic analyses have shown that plaque composition is related to the occurrence of acute clinical events and, therefore, to the vulnerability of the plaque. The emerging importance of adaptive coronary remodeling processes, such as the compensatory enlargement of the coronary artery in response to initial lesion development, has focused our interest on the nonstenotic lesions of the coronary tree. In vivo intravascular ultrasonography can demonstrate the discrepancies between the actual extent of coronary atherosclerosis and that seen by angiographic imaging. The spectral analysis of intravascular ultrasonography derived radiofrequency data enables more precise analysis of plaque composition and type than grayscale intravascular ultrasonography.