Atrial fibrillation is the most prevalent arrhythmia worldwide and remains one of the major causes of morbidity and mortality. Atrial fibrillation is an arrhythmia that has a various etiology and takes number of clinical forms. Due to the heterogenity of atrial fibrillation, it is necessary to individualize the optimal treatment strategy, ie conservative pharmacological therapy or interventional therapy as catheter ablation. Inncorrect indication of catheter ablation of atrial fibrillation leads to low success rate of the procedure and increases the risk of the procedure. The success rate of catheter ablation of atrial fibrillation depends on many clinical parameters, including the size and volume of the left atrium and the presence of pathological tissue in the atrial myocardium. In everyday practice, echocardiography (2D-echocardiography) is the most dominant method in estimation of the left atrial parameters, for it's simplicity, non- invasiveness, financial costs and the absence of ionizing radiation. Different methods for assesment of left atrial parameters are cardiac CT, cardiac magnetic resonance imaging and methods of 3-D echocardiography or 3-D angiography. The results of the present studies show that in patients with non-valvular atrial fibrillation who are indicated for catheter...

Computed tomography angiography (CTA) of the brain poses challenges on the imaging system; the contrast between blood vessels and surrounding soft tissue is very low, and to render small intricate vessel structures high spatial resolution is needed. Higher precision angiography would facilitate more accurate diagnosis of pathological conditions. The aim of this work was to analyze the factors which contribute to the image quality in cerebrovascular imaging contexts and make a comparison between state-of-the-art energy-integrating and photon counting CT systems. A geometrical model was devised to mimic the conditions of cerebral angiography. Different parameters and detectors were used to reconstruct images of a spherical head phantom. Compton noise was added to several image acquisitions after a Monte Carlo study was used to estimate the scatter to primary ratio (SPR) with a spherical phantom. The images were evaluated qualitatively and quantitatively. A real phantom was scanned with an experimental photon counting detector and compared with the simulated approach. The work resulted in qualitative reconstructed images, a decrease in SPR when introducing air gaps and improved resolution but worsened contrast as a result of smaller detector sizes. The SPR was shown to be higher in cone-beam geometry than fan-beam geometry. Electronic noise present with energy integrating detectors was shown to degrade image quality significantly in low dose imaging, reducing contrast when imaging vascular-like structures. Photon counting detectors without electronic noise could provide greater image quality and better diagnostic information.

No description available.

Adherence to guideline-recommended secondary cardiovascular prevention therapy (statins and cardiac rehabilitation) has been demonstrated to reduce the risk of all-cause mortality (Statins RRR 0.25, 95% CI 0.19-0.30; Cardiac Rehabilitation RRR 0.26, 95% CI 0.14-0.36) and secondary events.1,2 Yet, ≥50% of patients discontinue statin use within 12-month after an initial prescription and completion of cardiac rehabilitation is ≤20% in Ontario.3,4 Low statin adherence and cardiac rehab completion limits patients from realizing the full benefits of therapy. A meta-analysis of randomized controlled trials of adherence to statins for secondary prevention reported that nonadherence to statins was greater in non-white ethnicities compared to white ethnicities (OR 1.28, 95% CI 1.04-1.59) with geographical variation in outcomes.5 In respect to cardiac rehabilitation, the literature suggests that non-white ethnicities are less likely to complete cardiac rehabilitation compared to white participants.6,7 However, a gap remains in our knowledge of cardiac rehabilitation completion among immigrants due to lack of outcome reporting across clinical trials. The literature suggests that immigrants have improved health profiles relative to Canadian-born patients. Specifically, immigrants with ≤10 years of Canadian residency have greater medication adherence than immigrants with >10 of Canadian residency when compared to Canadian-born participants.6-9 This thesis was a planned sub-study of the Interventions Supporting Long-Term Adherence and Decreasing Cardiovascular Events (ISLAND) randomized control trial. The ISLAND study was a pragmatic, randomized controlled trial investigating the effect of educational reminders on adherence to guideline-recommended therapy post-myocardial infarction. Study participants were allocated in a 1:1:1 ratio to one of three groups: i) usual care, ii) educational reminders sent via post, or iii) combination post and interactive voice response educational reminders. Investigators were blinded to the allocation sequence, participant allocation, and outcome assessment. Medication adherence and completion of cardiac rehabilitation were assessed 12-months from baseline. This sub-study of ISLAND focused on participants who completed a 12-month outcome assessment with a recorded response to the following question, “Were you born a Canadian citizen?”. Immigrants experienced greater odds of statin adherence at 7-days (OR 1.36, 95% CI 1.00-1.85) and 30 days (OR 1.36, 95% CI 0.96-1.94) at one-year post-myocardial infarction, after adjusting for age, diabetes, sex, and smoking status. We found no evidence that immigration status was associated with cardiac rehabilitation completion (OR 0.91, 95% CI 0.72-1.14) after adjusting for age, diabetes, sex, smoking status, average neighborhood income quintile, education, and marital status. The odds of statin adherence at 7-days (OR 1.33, 95% CI 0.89-2.18) and 30-days (OR 1.39, 95% CI 0.89-2.18) was greater in visual minorities than white patients, however the difference was not statistically significant. We found no evidence of an association between ethnicity and cardiac rehabilitation completion (OR 0.98, 95% CI 0.75-1.29). Our analysis could not fully evaluate the healthy immigrant effect due to an insufficient sample size of immigrants with <10 years of Canadian residency exposure (n=29). In conclusion, we report a statistically significant 36% increase in the odds of 7-day and 30-day statin adherence in immigrants compared to Canadian-born patients. We also report that the odds of cardiac rehabilitation decreased by 9% in immigrants compared to Canadian-born patients at 12-months post-myocardial infarction but this was not statistically significant. Our findings offer support for the “healthy immigrant effect” continuing in immigrants with >10 years of Canadian residency exposure. We were unable to evaluate outcomes in immigrants with <10 years Canadian residency exposure due to a lack of sample size (n=29). / Thesis / Master of Science (MSc) / The primary purpose of this research project was to assess whether immigrants, individuals who reside in Canada but were born outside of the country, who have experienced a previous heart attack were adhere to heart health therapies better than Canadian-born patients. The heart health therapies of interest to our investigation are two guideline-recommended heart attack prevention therapies, statins and cardiac rehabilitation. The study design of our research project was a cohort sub-study of the ISLAND randomized control trial which investigated adherence to heart health therapies in patients residing in Ontario, Canada. Our major finding was that immigrants who lived in Canada for >10 years were more adherent to statin therapy for a previous heart attack compared to Canadian-born participants. Our findings support the hypothesis that immigrants tend to demonstrate behaviours associated with improved outcomes compared to their Canadian-born counterparts.

Background: The relevance of drusen-like deposits (DLD) in patients with systemic lupus erythematosus (SLE) is to a large extent uncertain. Their genesis is proposed to be correlated to immune-complex and complement depositions in the framework of SLE. The intention of this study was to determine potential morphological differences in the choroid and retina as well as potential microvascular changes comparing two cohorts of SLE patients divergent in the presence or absence of DLD using multimodal imaging. Methods: Both eyes of 16 SLE patients with DLD were compared to an age- and sex-matched control-group consisting of 16 SLE patients without detectable DLD. Both cohorts were treated with hydroxychloroquine (HCQ) and did not differ in the treatment duration or dosage. Using spectral-domain optical coherence tomography (SD-OCT) choroidal volume measures, choroidal vascularity indices (CVI) and retinal layer segmentation was performed and compared. In addition, by the exploitation of optical coherence tomography angiography vascular density, perfusion density of superficial and deep retinal capillary plexuses and the choriocapillaris were analyzed. For the choroidal OCT-scans, a subset of 51 healthy individuals served as a reference-group. Results: CVI measures revealed a significant reduction in eyes with DLD compared to healthy controls (0.56 (0.54−0.59) versus 0.58 (0.57−0.59) (p = 0.018) and 0.56 (0.54−0.58) versus 0.58 (0.57−0.60) (p < 0.001)). The photoreceptor cell layer presented significant thinning in both eyes of subjects with DLD compared to control subjects without DLD (68.8 ± 7.7 µm vs. 77.1 ± 7.3 µm for right eyes, p = 0.008, and 66.5 ± 10.5 µm vs. 76.1 ± 6.3 µm for left eyes, p = 0.011). OCTA scans revealed no significant changes, yet there could be observed numerically lower values in the capillary plexuses of the retina in eyes with DLD than in eyes without DLD. Conclusions: Our results illustrated significant alterations in the choroidal and retinal analyzes, suggesting a correlation between DLD and the progression of inflammatory processes in the course of SLE leading to retinal degeneration. For this reason, DLD could serve as a biomarker for a more active state of disease.

<p>Uvod: Pacijenti sa akutnim infarktom miokarda sa ST elevacijom treba da budu podvrgnuti reperfuzionoj terapiji, pre svega pPCI, bez obzira na životnu dob, ali zbog&nbsp; veće učestalosti komorbiditeta, faktora rizika za koronarnu bolest i vi&scaron;esudovne koronarne bolesti, kod pacijenata starije životne dobi, odluka o reperfuzionoj terapiji treba da se donese sa dobrom procenom odnosa rizik &ndash; benefit. Cilj: Utvrđene su razlike u kliničkoj slici, angiografskom nalazu, terapijskom pristupu, toku i ishodu akutnog infarkta miokarda sa ST elevacijom u starih osoba u odnosu na mlađu životnu dob (mlađi od 75 godina). Materijal i metode: U studiju je uključeno 240 pacijenata sa akutnim infarktom miokarda sa ST elevacijom, podeljeni u dve komparabilne grupe (120 bolesnika starijih i kontrolna grupa 120 mlađih od 75 godina), koji su izabrani metodom slučajnog izbora, po redosledu prijema u bolnicu. Za pacijente iz obe grupe popunjavan je upitnik, a tretirani su po jedinstvenom protokolu lečenja. Rezultati: U ispitivanom uzorku, u grupi bolesnika starijih od 75 godina reperfuziona terapija je bila primenjena u 85% slučajeva. Intrahospitalni mortalitet za ceo uzorak je 11,7% i u skladu je sa drugim istraživanjima [27]. Mortalitet u grupi pacijenata preko 75 godina je bio 12,5%, a u grupi pacijenata sa manje od 75 godina 10,8% (p=ns). Zaključak: Klinička slika bolesti kod bolesnika starije životne dobi je če&scaron;će atipična &scaron;to korelira sa drugim studijama [31, 35], a tok bolesti komplikovaniji i ishod lo&scaron;iji. Kod bolesnika starijih od 75 godina če&scaron;ća je vi&scaron;esudovna koronarna bolest. Primarna perkutana koronarna intervencija u akutnom infarktu miokarda sa ST elevacijom u pacijenata starije životne dobi potvrđuje benefit u lečenju, toku i ishodu bolesti.</p> / <p>Introduction: Patients with ST segment acute myocardial infarction should undergo reperfusion therapy, PCI in the first place, no matter their life age. However, due to high frequency of comorbidities, risk factors for coronary disease and multi-vessel coronary disease, the decision of reperfusion therapy in elderly patients should be made according to the good evaluation or risk benefit ratio. Aim: The differences have been determined in the clinical picture, angiographic finding, therapeutic approach, course and outcome of ST segment acute myocardial infarction in elderly patients in relation to younger life age (less than 75 years). Material and methods: The study included 240 patients with ST segment acute myocardial infarction. They were randomly divided into two comparable groups according to the date of their hospitalization (120 patients older than 75 and control group of 120 patients younger than 75 years). Both groups of patients filled out the survey and were treated according to the same protocol. Results: In the examined sample of the group of patients older than 75 the reperfusion therapy was performed in 85% of cases. Intrahospital mortality for the entire sample was 11.7% and is in coherence with other researches [27]. Mortality in the group of patients older than 75 years was 12.5%, and it was 10.8% (p=ns) in the group of patients younger than 75.&nbsp; Conclusion: Clinical picture of disease in elderly patients is atypical thus correlating with other studies [31, 35], and course of illness more complicated and with a worse outcome. Multi-vessel disease is more common in patients older than 75 years. Primary percutaneous coronary intervention in STEMI in elderly patients confirms benefits in treatment, course and outcome of disease.</p>

Collateral blood flow is the compensatory flow of blood to the tissue through secondary channels when the primary channel is compromised. It is of vital importance in cerebrovascular disease where collateral flow can maintain large regions of brain tissue which would otherwise have suffered ischaemic damage. Traditional x-ray based techniques for visualising collateral flow are invasive and carry risks to the patient. In this thesis novel magnetic resonance imaging techniques for performing vessel-selective labelling of brain feeding arteries are explored and developed to reveal the source and extent of collateral flow in the brain non-invasively and without the use of contrast agents. Vessel-encoded pseudo-continuous arterial spin labelling (VEPCASL) allows the selective labelling of blood water in different combinations of brain feeding arteries that can be combined in post-processing to yield vascular territory maps. The mechanism of VEPCASL was elucidated and optimised through simulations of the Bloch equations and phantom experiments, including its sensitivity to sequence parameters, blood velocity and off-resonance effects. An implementation of the VEPCASL pulse sequence using an echo-planar imaging (EPI) readout was applied in healthy volunteers to enable optimisation of the post-labelling delay and choice of labelling plane position. Improvements to the signal-to-noise ratio (SNR) and motion-sensitivity were made through the addition of background suppression pulses and a partial-Fourier scheme. Experiments using a three-dimensional gradient and spin echo (3D-GRASE) readout were somewhat compromised by significant blurring in the slice direction, but showed potential for future work with a high SNR and reduced dropout artefacts. The VEPCASL preparation was also applied to a dynamic 2D angiographic readout, allowing direct visualisation of collateral blood flow in the brain as well as a morphological and functional assessment of the major cerebral arteries. The application of a balanced steady-state free precession (bSSFP) readout significantly increased the acquisition efficiency, allowing the generation of dynamic 3D vessel-selective angiograms. A theoretical model of the dynamic angiographic signal was also derived, allowing quantification of blood flow through specified vessels, providing a significant advantage over qualitative x-ray based methods. Finally, these methods were applied to a number of patient groups, including those with vertebro-basilar disease, carotid stenosis and arteriovenous malformation. These preliminary studies demonstrate that useful clinical information regarding collateral blood flow can be obtained with these techniques.

Les artéfacts métalliques entraînent un épaississement artéfactuel de la paroi des tuteurs en tomodensitométrie (TDM) avec réduction apparente de leur lumière. Cette étude transversale prospective, devis mesures répétées et observateurs avec méthode en aveugle, chez 24 patients consécutifs/71 tuteurs coronariens a pour objectif de comparer l’épaisseur de paroi des tuteurs en TDM après reconstruction par un algorithme avec renforcement des bords et un algorithme standard. Une angiographie coronarienne par TDM 256 coupes a été réalisée, avec reconstruction par algorithmes avec renforcement des bords et standard. L’épaisseur de paroi des tuteurs était mesurée par méthodes orthogonale (diamètres) et circonférentielle (circonférences). La qualité d’image des tuteurs était évaluée par échelle ordinale, et les données analysées par modèles linéaire mixte et régression logistique des cotes proportionnelles. L’épaisseur de paroi des tuteurs était inférieure avec l’algorithme avec renforcement des bords comparé à l’algorithme standard, avec les méthodes orthogonale (0,97±0,02 vs 1,09±0,03 mm, respectivement; p<0,001) et circonférentielle (1,13±0,02 vs 1,21±0,02 mm, respectivement; p<0,001). Le premier causait moins de surestimation par rapport à l’épaisseur nominale comparé au second, avec méthodes orthogonale (0,89±0,19 vs 1,00±0,26 mm, respectivement; p<0,001) et circonférentielle (1,06±0,26 vs 1,13±0,31 mm, respectivement; p=0,005) et diminuait de 6 % la surestimation. Les scores de qualité étaient meilleurs avec l’algorithme avec renforcement des bords (OR 3,71; IC 95% 2,33–5,92; p<0,001). En conclusion, la reconstruction des images avec l’algorithme avec renforcement des bords génère des parois de tuteurs plus minces, moins de surestimation, et de meilleurs scores de qualité d’image que l’algorithme standard. / Metallic artifacts can result in an artificial thickening of the coronary stent wall which can significantly impair computed tomography (CT) imaging in patients with coronary stents. The purpose of this study is to assess the in vivo visualization of coronary stent wall and lumen with an edge-enhancing CT reconstruction kernel, as compared to a standard kernel. This is a prospective cross-sectional study of 24 consecutive patients with 71 coronary stents, using a repeated measure design and blinded observers, approved by the Local Institutional Review Board. 256-slice CT angiography was used, as well as standard and edge-enhancing reconstruction kernels. Stent wall thickness was measured with orthogonal and circumference methods, averaging wall thickness from stent diameter and circumference measurements, respectively. Stent image quality was assessed on an ordinal scale. Statistical analysis used linear and proportional odds models. Stent wall thickness was inferior using the edge-enhancing kernel compared to the standard kernel, either with the orthogonal (0.97±0.02 versus 1.09±0.03 mm, respectively; p<0.001) or circumference method (1.13±0.02 versus 1.21±0.02 mm, respectively; p<0.001). The edge-enhancing kernel generated less overestimation from nominal thickness compared to the standard kernel, both with orthogonal (0.89±0.19 versus 1.00±0.26 mm, respectively; p<0.001) and circumference (1.06±0.26 versus 1.13±0.31 mm, respectively; p=0.005) methods. The average decrease in stent wall thickness overestimation with an edge-enhancing kernel was 6%. Image quality scores were higher with the edge-enhancing kernel (odds ratio 3.71, 95% CI 2.33–5.92; p<0.001). In conclusion, the edge-enhancing CT reconstruction kernel generated thinner stent walls, less overestimation from nominal thickness, and better image quality scores than the standard kernel.

La fraction d’éjection du ventricule gauche est un excellent marqueur de la fonction cardiaque. Plusieurs techniques invasives ou non sont utilisées pour son calcul : l’angiographie, l’échocardiographie, la résonnance magnétique nucléaire cardiaque, le scanner cardiaque, la ventriculographie radioisotopique et l’étude de perfusion myocardique en médecine nucléaire. Plus de 40 ans de publications scientifiques encensent la ventriculographie radioisotopique pour sa rapidité d’exécution, sa disponibilité, son faible coût et sa reproductibilité intra-observateur et inter-observateur. La fraction d’éjection du ventricule gauche a été calculée chez 47 patients à deux reprises, par deux technologues, sur deux acquisitions distinctes selon trois méthodes : manuelle, automatique et semi-automatique. Les méthodes automatique et semi-automatique montrent dans l’ensemble une meilleure reproductibilité, une plus petite erreur standard de mesure et une plus petite différence minimale détectable. La méthode manuelle quant à elle fournit un résultat systématiquement et significativement inférieur aux deux autres méthodes. C’est la seule technique qui a montré une différence significative lors de l’analyse intra-observateur. Son erreur standard de mesure est de 40 à 50 % plus importante qu’avec les autres techniques, tout comme l’est sa différence minimale détectable. Bien que les trois méthodes soient d’excellentes techniques reproductibles pour l’évaluation de la fraction d’éjection du ventricule gauche, les estimations de la fiabilité des méthodes automatique et semi-automatique sont supérieures à celles de la méthode manuelle. / Left ventricular ejection fraction is an excellent indicator of cardiac function. Many invasive and non-invasive techniques can be used for its assessment: angiography, echocardiography, cardiac MRI, computed tomography of the heart, multigated radionuclide angiography and myocardial perfusion imaging. More than 40 years of scientific publication praise the multigated radionuclide angiography for its execution speed, its availability, its low cost and intrarater and interrater reproducibility. The left ventricular ejection fraction was calculated twice for 47 patients, using two raw data acquisitions, two technologists and three software platforms: one fully manual, one semi-automatic and one fully automatic. In general, the automatic and semi-automatic methods showed greater reproducibility, a smaller standard error of measurement and minimal detectable change than the manual method, whereas the manual method systematically gave a significantly lower quality of result. It was the only technique that showed significant intrarater difference, and its standard error of measurement and minimal detectable change were 40% to 50% higher than those of automatic and semi-automatic methods. Even though all three techniques are all excellent and reliable options, reliability coefficient estimations were superior using automatic and semi-automatic methods as compared to the manual method.

No description available.