Carotid atherosclerosis, one of the leading causes of ischemic stroke worldwide, can induce severe narrowing or even occlusion of the vessel, restricting blood flow to the brain and resulting in perfusion deficits. The plaque that has a high probability of undergoing rapid progression or future ruptures is defined as “vulnerable plaque”. Identifying vulnerable plaque is of great importance in clinical carotid atherosclerosis imaging. To date, a multi-contrast magnitude-based MR approach with blood suppression technique has been widely used to detect vulnerable plaque features. However, due to the limitations of magnitude-based methods, developing new MR techniques that have better sensitivity to hemorrhage and calcification is of great interest. Quantitative Susceptibility Mapping (QSM) is a technique that utilizes the MR phase information and has been widely used for quantifying the tissue susceptibility in the brain. The susceptibility contrast is extremely sensitive to hemorrhage and calcium which makes QSM a potential tool for carotid plaque imaging to identify intraplaque hemorrhage (IPH) and calcification. However, existing QSM methods have not been successfully implemented in the neck due to several challenges. The presence of air/tissue interface, plaque that has high susceptibility, and fat surrounding the carotid arteries can cause severe phase aliasing and other problems that will induce errors in the resultant susceptibility maps. To overcome these challenges and thus, develop a robust method for carotid QSM, a protocol that includes both data acquisition strategy and post-processing methods is proposed. For data acquisition, four echoes including two water/fat in-phase echoes and two water/fat out-of-phase echoes were collected. For data post-processing, temporal domain algorithm Catalytic Multiecho Phase Unwrapping Scheme (CAMPUS) was used to unwrap the phase images and local QSM was proposed. This protocol is able to properly unwrap the phase images even with the presence of high susceptibility plaque and eliminate the water/fat chemical shift effect in QSM reconstructions which will generate reliable susceptibility maps. From our results, the proposed QSM protocol has demonstrated the ability to generate reliable susceptibility maps and excellent sensitivity to IPH and calcification. Combining QSM with existing magnitude-based methods will lead to a major improvement in the diagnosis of carotid atherosclerosis. / Thesis / Master of Applied Science (MASc)

A partir des données de 2 études de population menées chez des sujets âgés, non institutionnalisés, respectivement l’étude des 3 Cités et l’étude EVA (Epidémiologie du Vieillissement Artériel), nos objectifs étaient 1) de revisiter le rôle de l’athérosclérose carotidienne dans son association avec les évènements coronaires et avec les démences, en dissociant précisément l’athérome (i.e. les plaques carotidiennes ; PC) de l’hypertrophie artérielle (i.e. l’épaississement diffus de l’intima-média mesuré au niveau de l’artère carotide commune ; EIM-ACC) et 2) dans un objectif plus mécanistique, d’analyser le lien différentiel entre l’athérome, l’hypertrophie artérielle et l’un des polymorphismes nucléotidiques (rs1333049) les plus associés à la maladie coronaire et situé sur le chromosome 9 (locus 9p21).Dans un 1er travail, nous avons montré que les PC étaient associées à une augmentation du risque d’évènement coronaire à 6 ans, à l’inverse de l’EIM-ACC qui n’était pas associée au risque coronaire. De plus l’ajout des PC à un modèle comprenant les FDRCV améliorait significativement la prédiction du risque coronaire avec près de 12% des sujets correctement reclassés en terme de risque prédit (NRI = 11,7% ; IC95% = 3,1%-20,0%). Dans la seconde analyse (3C et EVA), nous avons mis en évidence une association spécifique entre les PC et le polymorphisme nucléotidique rs1333049 (OR allèle C = 1,24 ; IC 95% = 1,13-1,36). Chez les sujets de la cohorte EVA, l’allèle C était également associé à la progression des plaques carotidiennes à 4 ans, mais pas à la progression de l’EIM. Dans le dernier volet de cette thèse et de manière similaire aux évènements coronaires, il existait une association spécifiques entre les PC et la survenue de démences vasculaires/mixtes à 7 ans (HR ≥ 2 sites avec plaques vs. 0 = 1,93 ; IC 95% = 1,13-3,28). Aucune association n’était retrouvée avec l’EIM. L’ajout des plaques carotidiennes à un modèle comprenant les FDR CV et de démence permettait de reclasser correctement 43% des sujets en terme de risque de DVasc (NRI=43,0% ; IC95% = 20,2-66,2). Enfin, dans le cadre de cette thèse, nous participons à un travail collaboratif portant sur la progression individuelle de l’EIM au cours du temps en association avec la survenue d’évènements cardiovasculaires. Les données de EVA ont été intégrées à ce projet. Un premier résultat de cette méta-analyse était que la progression annuelle de l’EIM-ACC n’était associée à aucun des évènements cardiovasculaires étudiés. Au total, les résultats de cette thèse indiquent la présence d’une association différentielle des plaques carotidiennes et de l’EIM-ACC avec les évènements coronaires et les démences. Les implications sur le plan de la prévention et en termes de cibles thérapeutiques potentielles sont discutées dans cette thèse. / Using data from 2 large French cohorts of non-institutionalized older adults, namely the Three-City Study (3C) and the Vascular Aging Study (EVA), we aimed 1) to explore the respective contribution of ultrasound detected carotid plaques (e.g. atherosclerosis) and diffuse common carotid intima-media thickness (CCA-IMT) (e.g. arteriosclerosis) to incident coronary events and dementia and 2) to assess the differential relationship between carotid plaques, CCA-IMT and the coronary heart disease (CHD)-associated single polymorphism nucleotide (rs1333049) on chromosome 9p21. First, we showed that carotid plaques but not CCA-IMT were associated with an increased risk of 6-year CHD. Furthermore, carotid plaques significantly improved CHD risk prediction beyond traditional CV risk factors, as nearly 12% of the participants were correctly reclassified in terms of predicted risk(Net Reclassification Improvement (NRI) = 11.7%; 95% CI = 3.1%-20.0%). In our second analysis, including subjects from both 3C and EVA, we found a specific association between carotid plaques and the rs1333049 genotype (OR C allele at risk= 1.24; 95% CI = 1.13-1.36). Moreover, among the EVA participants, the rs1333049 genotype was also associated with carotid plaques progression over 4 years, but not with CCA-IMT progression. Thirdly, we showed a specific relationship between carotid plaques and the occurrence of 7-year vascular/mixed dementia (VaD) (HR ≥ 2 sites with plaques vs. 0 = 1.93; 95% CI = 1.13-3.28). No relationship was found for CCA-IMT. Furthermore, adding carotid plaques to a model including vascular and dementia risk factors resulted in a significant continuous NRI of 43.0% (95% CI = 20.2%-66.2%) for VaD. At last, in line with the present work, we currently participate through the EVA Study to a collaborative project on the relationship between individual IMT progression over time and cardiovascular risk. A first result recently published, showed the absence of relationship between yearly IMT progression and cardiovascular events. In summary, the present work indicates that carotid plaques and CCA-IMT are differentially associated with coronary events and vascular/mixed dementia. Potential implications of our results regarding primary prevention and therapeutic targets are discussed in this thesis.

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.

Ischemic stroke is the most common cause of handicap in adults and the third most common cause of death in Sweden. Internal carotid artery atherosclerosis is an important cause and accounts for 20% of ischemic strokes. Screening for carotid atherosclerosis has been debated over the past two decades. The aims of this thesis were (I) to study the prevalence of and risk factors associated with carotid artery atherosclerosis among 65 year old men, (II) to evaluate a simplified ultrasound protocol (the grayscale/mosaic method) for the exclusion of significant carotid artery stenosis for screening purpose, (III) to evaluate the required effect of primary preventive therapy in reducing risk of stroke among patients with asymptomatic carotid disease in order for screening to be cost-effective and (IV) to study natural history of carotid atherosclerosis and outcome five years after screening in 65-year old men. The prevalence of atherosclerotic plaques was high (25%), while the prevalence of >50% stenosis was relatively low (2.0%). Smoking, hypertension, diabetes mellitus and coronary artery disease were independent risk factors and individuals with several risk factors had a higher prevalence of stenosis. Most of those at risk were not on any preventive medication. A simplified grayscale/mosaic method was found to have a high negative predictive value for significant carotid stenosis. The minimum stroke risk reduction effect required for preventive intervention to be cost effective was 22%. Carotid atherosclerotic plaque and stenosis 50-79% has a relatively benign development during five years if treated with BMT and risk factor adjustment. Very few progressed to symptomatic disease. More severe stenosis (80-99%) had higher rate of neurological events, and may benefit from additional intervention. In conclusion, prevalence of silent atherosclerotic disease in carotid arteries was common among 65-year-old men. Most of those at risk had no secondary prevention. There is a simple DUS method that could be used for screening purpose. Screening for carotid disease is only cost-effective if the preventive strategy lowers the risk of stroke by 22%. Men with plaques and moderate stenosis have a good prognosis, but among those with severe stenosis there is a need for further intervention. / Screening for asymptomatic carotid atherosclerosis

Systemic lupus erythematosus (SLE) is a chronic inflammatory disease of high morbidity and mortality associated mainly with the activity of disease, infections and cardiovascular disease. In this condition, both premature atherosclerosis (AT) as well as left ventricular hypertrophy (LVH) are related to traditional risk factors for cardiovascular disease (CVD) and probably the peculiar characteristics of the pathophysiology of inflammatory disease. Some evidence shows the association of AT and LVH, which is considered a strong predictor for the presence of atherosclerotic plaques in carotid arteries. This study aimed to determine the frequency of AT and LVH in patients with SLE and to evaluate its relationship with traditional risk factors and factors specific to the disease. We conducted a prospective study of 70 SLE patients attending the outpatient clinic of Rheumatology, Federal University of Sergipe (UFS) and Private Practice of Rheumatology. We evaluated clinical, laboratory and research intima-media thickness of carotid arteries (CIMT) in atherosclerotic plaques and the index of left ventricular mass (LVMI), through questionnaires, the completion of the carotid duplex scan and echocardiogram, respectively. Statistical analysis was determined by multiple logistic regression, after performing descriptive statistics and odds ratios adjusted and simple. We observed the presence of AT in 34.3% of cases, LVH in 45.7% and concomitant LVH with AT in 23% of cases. AT was significantly associated with age > 50 years, systolic blood pressure (SBP), dyslipidemia, non-white race, renal disease, absence of antimalarial, late age of diagnosis, time course of disease and LVH, (p<0.05). In multivariate analysis, the relationship was demonstrated age > 50 years (OR:7.3), p = 0.01, absence of antimalarial (OR:4.7), p=0.006 and SBP (OR:1.5), p=0.05. LVH was associated with age > 50 years, not white race, hypertension (HBP), c-reactive protein > 1 mg/dL (CRP), time course of disease and AT (p <0.05). In the multivariate analysis, we found that hypertension (OR:11.4), p=0.001, CRP > 1 mg/dL (OR:8.2), p=0.004, AT (OR:6.04); p=0.02, remained linked to LVH and body mass index (BMI) > 25 kg/m² (OR:4.61), p=0.04, was added as a strong predictor of LVH. The data suggest that in SLE, the presence of AT and LVH are associated not only to some traditional risk factors for CVD such as hypertension and obesity, but also to the chronicity of the disease, its treatment; and serological markers of inflammation. / O lúpus eritematoso sistêmico (LES) é uma doença inflamatória crônica de elevada morbidade e mortalidade associada, sobretudo, à atividade de doença, infecções e doença cardiovascular. Nessa afecção, tanto a aterosclerose prematura (AT) como a hipertrofia ventricular esquerda (HVE) encontram-se relacionadas a fatores de risco tradicionais para doença cardiovascular (DCV) e provavelmente, a características peculiares na fisiopatogênese dessa doença. Algumas evidências demonstram a associação da AT e HVE, sendo esta considerada um forte preditor para a presença de placas ateroscleróticas nas carótidas. O presente estudo teve como objetivo determinar a frequência de AT e HVE em pacientes com LES e avaliar sua relação com fatores de risco tradicionais e fatores próprios da doença. Foi realizado um estudo prospectivo em 70 pacientes portadores de LES, atendidos no ambulatório de Reumatologia da Universidade Federal de Sergipe (UFS) e consultório particular de Reumatologia. Foram avaliados dados clínicos, laboratoriais e pesquisa da espessura médio-intimal das carótidas (EIMC), de placas ateroscleróticas e do índice de massa do ventrículo esquerdo (IMVE), por intermédio de questionário, da realização do duplex scan de carótidas e do ecocardiograma, respectivamente. A análise estatística foi determinada pela regressão logística múltipla, após realização de estatística descritiva e cálculo de odds ratio (OR) simples e ajustado. Observou-se a presença de AT em 34,3% dos casos, a HVE, em 45,7% e concomitância de AT com HVE em 23% dos casos. Na análise univariada, a AT associou-se significativamente à idade > 50 anos, pressão arterial sistólica (PAS), dislipidemia, raça branca, doença renal, ausência de antimalárico, idade tardia de diagnóstico, tempo longo de doença e HVE; (p<0,05). Em análise multivariada, a relação demonstrada foi idade > 50 anos, (OR:7,3); p=0,01, ausência do antimalárico, (OR:4,7); p=0,006 e pressão arterial sistólica (PAS) (OR:1,5); p=0,05. A HVE esteve associada à idade > 50 anos, cor não branca, hipertensão arterial sistêmica (HAS), proteína c reativa (PCR) > 1mg/dL, tempo longo de doença e AT, (p<0,05). Já na análise multivariada, observou-se que HAS (OR:11,4); p=0,001, PCR > 1 mg/dL, (OR:8,2); p=0,004 e AT (OR:6,04) ; p=0,02, permaneceram relacionadas à HVE e o índice de massa corpórea (IMC) > 25 kg/m² (OR:4,61); p=0,04, foi acrescentado como forte preditor de HVE. Os dados sugerem que, no LES, as presenças de AT e HVE estão associadas não somente a alguns fatores de risco tradicionais para DCV, como a HAS e obesidade, mas também à cronicidade da doença, tratamento instituído e marcadores inflamatórios da doença.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Insulin-Like growth factor I (IGF-I) is a peptide that has an important action on cell division, differentiation, migration and apoptosis for vascular smooth muscle cells (VSMCs), may intervene in atherosclerosis. It antiapoptotic factor and it also stimulates. Thus, potential reductions in IGF-I effects might be beneficial in certain pathologic conditions, such as hypertension and the early stages of atherosclerosclerotic plaque formation characterized by hypertrophy/hyperplasia of VSMCs, but detrimental in other conditions in which loss of VSMCs contributes to the disease process, such as destabilization of atherosclerotic plaques. Conversely, it has been suggested that serum IGF-1 levels are low in patients with coronary heart disease. Recently, we have described a GH naïve homogeneous population with a monogenic mutation that inactives the growth hormone-releasing hormone receptor (GHRHR) (IVS1+ 1GA) with extremely low levels of IGF-1. Moreover, they also presented central obesity, higher levels of systolic blood pressure and dyslipidemia unique opportunity to evaluate the impact of extremely low levels of IGF-1 on the myocardial ischemic and carotid atherosclerosisis in high risk cardiovascular population, pertaining to the research object. It has been studied 22 dwarfs with GHD and no past of growth hormone therapy (10M:12F; 44±12 yrs) and compared to 26 age-matched normal subjects, control group[CO]. It has been examined clinical, biochemical data, including insulin-like growth factor 1(IGF-1), rest and exercise echodopplercardiography and, carotid intima-media thickness by a high-resolution carotid ultrasonography. IGF-1 in GHD group was markedly lower (3,3±5,5 vs 228,4±134,7ng/Ml; p<0.001) and fasting insulin (3,37±3,9 vs 3,59±3,0 microU/mL; p=NS) were smaller but not significantly in GHD. In the resting echocardiographic study, we observed normal indices of both systolic and diastolic function. During exercise treadmill (Bruce Protocol), both groups reached similar peak heart rate (162±16,5 vs 168±15,7bpm; p=NS) and peak systolic blood pressure (49±20 vs 59,4±23,6mmHg p=NS). Comparison of exercise wall motion score index in GHD group (1±0.0) vs CO group (1±0.0) did not show differences. Moreover, intima-media thickness measured at the far wall of the distal common carotid artery (0,59 ± 0,10 mm vs 0,60 ± 0,14 mm; p=NS (GHD vs CO group) was not indicative of premature atherosclerosis in GHD population. Only one of the subjects in the population studied presented carotid atherosclerotic plaque. Our data suggest that in a very homogeneous population with isolated GHD is not associated with premature carotid atherosclerosis or a higher prevalence of myocardial ischemia. Extremely low levels of the IGF-1 may be a protective mechanism against premature atherosclerosis in this apparently high risk selected group. / O fator do crescimento semelhante a insulina (IGF-I) é um peptídeo que tem importante ação sobre a divisão, diferenciação, migração e apoptose das células musculares lisas vasculares (CMLVs) e que pode interferir no mecanismo da aterosclerose. Assim a redução potencial do IGF-I pode ser benéfica em certas condições patológicas, tais como hipertensão e estágios iniciais da formação de placas ateroscleróticas caracterizadas por hipertrofia/hiperplasia das CMLVs, mas danoso em outras condições nas quais a perda de CMLVs contribui para o processo da doença, tais como desestabilização das placas ateroscleróticas. Porém, tem sido sugerido que níveis séricos de IGF-I estão baixos em pacientes com doença arterial coronariana. Recentemente, foi descrita uma população homogênea com uma mutação monogênica no gene receptor do hormônio regulador do hormônio do crescimento (GHRH-R) (IVS1+ 1GA) com deficiência isolada do hormônio do crescimento (DIGH) e níveis extremamente baixos de IGF-1. Apresentavam obesidade central, níveis elevados de pressão arterial sistólica e dislipidemia, oportunidade única para avaliar o impacto de níveis extremamente baixos de IGF-I na isquemia miocárdica e aterosclerose carotídea em população de alto risco, objetivo do nosso trabalho. Foram estudados 22 anões nunca tratados com DIGH (10M:12F; 44±12 anos) e comparados com 26 indivíduos normais de mesma idade e região, grupo controle (CO). Foram analisados: dados clínicos, bioquímicos, eletrocardiograma, ecocardiograma em repouso e exercício e duplex scan das carótidas (DSC) para quantificação da espessura médio-intimal das carótidas e pesquisa de placa aterosclerótica. Os resultados encontrados indicaram que o IGF-1 no grupo DIGH estava marcadamente baixo (3,3±5,5 vs 228,4±134,7ng/Ml; p<0,001) e a insulina de jejum (3,37±3,9 vs 3,59±3,0 microU/mL; p=NS) estava mais baixa, mas não significativa no DIGH. No estudo do ecocardiograma de repouso foi observado funções sistólica e diastólica normais. Durante o exercício na esteira ergométrica, ambos os grupos obtiveram semelhante pico de freqüência cardíaca (162±16,5 vs 168±15,7bpm;p=NS) e delta de pressão sistólica (49±20 vs 59,4±23,6mmHg; p=NS). Comparando-se o índice de escore de motilidade do VE no grupo DIGH (1±0.0) vs grupo (CO) (1±0.0) não demonstrou diferenças. A análise comparativa da espessura médio-intimal das carótidas,entre as populações dos grupos DIGH vs grupo (CO) não demonstrou diferença significativa (0,59 ± 0,10 mm vs 0,60 ± 0,14 mm), não foi demonstrado aterosclerose prematura na população com DIGH. Apenas um portador de DIGH apresentou placas ateroscleróticas. Nossos dados sugerem que a deficiência isolada DIGH associada com baixos níveis do IGF-1 não se associou com aterosclerose prematura e alta prevalência de isquemia miocárdica. Foi especulado que níveis extremamente baixos do fator de crescimento IGF-1 pode ter mecanismos protetores contra aterosclerose prematura, apesar de apresentarem um grupo de fatores de elevado risco cardiovascular.