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Carotid IM-GSM is more accurate than conventional IMT for monitoring systemic burden of atherosclerosis
Umeå University.
Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Cardiology.
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(English)Manuscript (preprint) (Other academic)
National Category
Cardiac and Cardiovascular Systems
Identifiers
URN: urn:nbn:se:umu:diva-111073OAI: oai:DiVA.org:umu-111073DiVA: diva2:866788
Available from: 2015-11-03 Created: 2015-11-03 Last updated: 2015-12-04
In thesis
1. Patterns of non-invasive imaging of carotid atherosclerosis
Open this publication in new window or tab >>Patterns of non-invasive imaging of carotid atherosclerosis
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Atherosclerosis is an inflammatory disease that can be generalized, affecting more than one arterial bed simultaneously, or localized, manifested in one system. Ultrasound based measurements of plaque textural features, such as low grey scale median (GSM), echolucent (hypoechoic) plaque types and juxtaluminal black (hypoechoic) area (JBA) are manifestation of potentially unstable lesions. Conventional carotid IMT (intima media thickness) and the recently introduced IM-GSM (echogenicity of the intima media complex) are important measures of subclinical atherosclerosis and are used to predict future ischemic events.

The aims of this thesis were to study, in detail, the systemic nature of atherosclerosis by evaluating the carotid disease burden contralateral to symptomatic arteries, determining the relationship between proximal (subclinical atherosclerosis) and distal segments (well established disease) of the same artery and comparing local plaque features with systemic burden of atherosclerosis disease. In addition, the effect of statins on carotid plaque echogenicity was evaluated in a systematic review and meta-analysis.

Methods:

We have measured ultrasound-based textural carotid plaque features (GSM, JBA, entropy, coarseness), surface morphology, as well as IMT and IM-GSM. An in-house custom developed research software package was used for plaque feature extraction. For the meta-analysis we used Comprehensive Meta-Analysis version 3 software.

Results:

Study 1. In 39 patients, the carotid plaques contralateral to symptomatic arteries had similar morphological and textural features to those in the symptomatic arteries and are more vulnerable than those in asymptomatic arteries; more often mildly or markedly irregular with more vulnerable textural plaque features (lower GSM and larger JBA).

Study 2. In 87 asymptomatic patients, an increased IMT in CCA correlated with plaque irregularities in the bifurcation and ICA while IM-GSM was closely related to plaque echogenicity (GSM), and other textural plaque features.

Study 3. In the same cohort in study 2, patients with previous disease in the coronary arteries had higher IMT and lower IM-GSM and those with prior stroke had lower IM-GSM. Neither IMT nor IM-GSM was different between patients with and without previous lower extremity disease. IM-GSM decreases significantly with increasing number of arterial territories p<0.001 (asymptomatic vs symptoms in one vs multiple arterial systems) but conventional IMT was not different between groups p=0.49.

Study 4. In a meta-analysis of 9/580 identified studies including 566 patients with 7.2 months follow-up, a consistent increase in the carotid plaques echogenicity after statin therapy, was reported. The perpetual (over 12 months) effects of which were shown in a meta-regression analysis to be related to changes in hsCRP.

Conclusion:

Symptomatic patients have similar plaque morphology and textural features of vulnerability in the contralateral carotid system, compared with asymptomatic ones. In the latter, measurements of proximal disease reflect distal pathology and the number of affected arteries. Finally, statin therapy and the drop of LDL cholesterol result in better plaque stability and optimum control of arterial inflammation, shown by arterial wall echogenicity and hsCRP changes, respectively.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 87 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1759
National Category
Cardiac and Cardiovascular Systems
Research subject
Cardiology
Identifiers
urn:nbn:se:umu:diva-110969 (URN)978-91-7601-363-2 (ISBN)
Public defence
2015-11-25, hörsal B, Unod T9, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-11-04 Created: 2015-11-01 Last updated: 2015-11-06Bibliographically approved
2. Carotid artery disease: plaque features and vulnerability
Open this publication in new window or tab >>Carotid artery disease: plaque features and vulnerability
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Background: Atherosclerosis is an important cause of stroke. Ultrasound offers the convenience of real-time and detailed assessment of carotid plaque features as well as arterial wall thickening and composition. Evaluation of these features is important for determining patients’ risk of suffering vascular events and also contributes to selecting the best treatment strategy.

Methods: Using ultrasound data analysis we have determined plaque features in the bifurcation and internal carotid artery (ICA), including: surface plaque irregularities, calcification, echogenicity (grey scale median-GSM) and other textural plaque features (Juxtaluminal black area, entropy, coarseness). In addition, intima media thickens (IMT) and its grey scale median (IM-GSM) was measured in common carotid artery (CCA). Using Cone Beam CT (CBCT) we have quantified calcification volume of the carotid plaques extracted after carotid endarterectomy procedure. For the meta-analysis we have used comprehensive meta-analysis software version 3. Study I: We have included 39 patients and we compared carotid plaque features of the contralateral arteries with those located ipsilateral to symptomatic side and arteries of asymptomatic patients.

Study II: The accuracy of US to detect atherosclerosis calcification was assessed against CBCT in 88 patients. Study III: Based on the previous vascular events in coronary, carotid and lower extremity arterial system, 87 patients were divided into three groups: asymptomatic, symptoms in one vascular system and symptoms in more that one vascular system. IMT, IM-GSM and plaque features were compared between groups.

Study IV: We have meta-analyzed ten cohort prospective studies evaluating carotid plaque echogenicity for cerebrovascular symptoms prediction. Results: Study I. Plaques of the contralateral to symptomatic arteries had similar features to those in symptomatic and more vulnerable than asymptomatic arteries.

Study II. Carotid ultrasound was accurate in detecting calcification volumes of ≥8mm3 with very high sensitivity but it was less accurate in detecting lower calcification volumes (<8mm3). Carotid calcification was not different between symptomatic and asymptomatic patients. Study III. Echogenicity of the intima-media complex (IM-GSM), but not its thickness (IMT), was significantly decreased with increasing number of arterial systems affected by atherosclerosis. IM-GSM was lower in patients with prior myocardial infarction and stroke.

Study IV. Carotid plaque echogenicity evaluated by US could predict future cerebrovascular events in patients with asymptomatic, relative risk RR 2.72 (95% CI, 1.86 to 3.96), and recurrent symptoms in symptomatic patients, RR 2.97 (95% CI, 1.85-4.78). Conclusion: Plaques located in the contralateral to symptomatic arteries have similar features as

symptomatic side and more vulnerable than asymptomatic arteries. Carotid ultrasound could accurately detect larger but not smaller carotid plaque calcification volumes (<8 mm3). Low IM- GSM could identify patients with multi-system atherosclerosis disease, suggesting a better marker for determining systemic atherosclerosis disease burden compared to conventional IMT. Finally, carotid plaque echogenicity predicts future cerebrovascular events in patients with symptomatic and asymptomatic carotid stenosis. 

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. 86 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1760
Keyword
Carotid atherosclerosis, ultrasound, plaque features, echogenicity, calcification, surface plaque irregularities, subclinical atherosclerosis, cerebrovascular symptoms
National Category
Cardiac and Cardiovascular Systems
Research subject
Cardiology; Medicine, cardiovascular disease
Identifiers
urn:nbn:se:umu:diva-111048 (URN)978-91-7601-364-9 (ISBN)
Public defence
2015-11-26, hörsal D, Unod T9., Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2015-11-05 Created: 2015-11-02 Last updated: 2015-11-06Bibliographically approved

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