Magnetic resonance imaging is often used as a source for reconstructing vascular anatomy for the purpose of computational fluid dynamics (CFD) analysis. We recently observed large discrepancies in such “image-based” CFD models of the normal common carotid artery (CCA) derived from contrast enhanced MR angiography (CEMRA). A novel quantitative comparison of velocity profile shape of N=20 cases revealed an average 25% overestimation of velocities by CFD, attributed to a corresponding underestimation of lumen area in the CEMRA-derived geometries. We hypothesized that this was due to blurring of edges in the images caused by dilution of contrast agent during the relatively long elliptic centric CEMRA acquisitions, and confirmed this with MRI simulations. CFD simulations incorporating realistic inlet velocity profiles and non-Newtonian rheology had a negligible effect on velocity profile skewing, suggesting a role for other sources of error or modeling assumptions.

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This thesis is a step forward in evaluating insulin therapy and defining its role in cardiac surgery first described as Glucose-Insulin-Potassium (GIK) solution 40 years ago. / Chapter (I) includes a review of the literature on insulin therapy in cardiac surgery and illustrates the scientific bases and controversies in this therapy. / Chapter (II) entitled: "Myocardial Protection During Elective Coronary Artery Bypass Grafting Using High Dose Insulin Therapy" represents a manuscript that was presented in the following meetings: (A) Local meetings: (1) McGill cardiovascular research day, February 1/2007, Montreal, Canada. (2) Fraser Gurd annual research day, McGill surgery department, May 31/2007, Montreal, Canada. (B) National meetings: (1) 11th Annual Terrence Donnelly research day for Canadian cardiac surgery residents, May 26/2007, Toronto, Canada. (C) International meetings: (1) 43rd Annual meeting of the Society of thoracic surgeons (STS), January 30/2007, San Diego, United States. A full manuscript was submitted to "The Annals of Thoracic Surgery" for review. / Chapter (III) entitled: "High Dose Insulin Therapy Attenuates Systemic Inflammatory Response in Patients Undergoing Elective Coronary Artery Bypass Grafting" represents a manuscript that was presented in the following meetings: (A) Local meetings: (1) Fraser Guard McGill Surgery department annual research day, May 3/2006, Montreal, Canada. (B) National meetings: (1) 10th Annual Terrence Donnelly research day for Canadian cardiac surgery residents, May 26/2007, Toronto, Canada. (2) Young investigator forum, Canadian Society of Clinical Investigators (CSCI), September 28/2006, Ottawa, Canada. (3) 59 th annual meeting of Canadian Cardiovascular Society (CCS), October 21/2006, Vancouver, Canada. (C) International meetings: (1) American Heart Association (AHA), November 12/2006, Chicago, United states. / Abstracts from this work were published in the following journals: (1) Clinical and Investigative Medicine, Vol. 29, No. 4, August 2006. (2) The Canadian Journal of Cardiology, Vol. 22 supp D, October 2006 (3) Circulation, Vol. 114 supp, No. 18, October 2006. / A full manuscript was submitted to "the journal of thoracic and cardiovascular surgery" for review.

The aim of the study is to evaluate the efficacy of percutaneous transluminal angioplasty in reduction of the lower limb ischemia and to investigate the influence of this procedure on the lower limb salvage rate. The introduction defines the objectives and tasks of the study, includes a literature review, a summary of the main problems related to the theme. A separate chapter describes the research methodology. The study analysed the treatment results of 146 patients who underwent the iliac artery percutaneous transluminal angioplasty. The following PTA efficacy criteria were determined - the increase of ankle-brachial index and the decrease of ischemia according to Fontaine stages of limb ischemia. It was also found that the substantial PTA effect of the iliac artery and the need for additional interventions become evident during the early postoperative period (1–7 days after PTA), and the effect of angioplasty decreases gradually during one year follow-up after the procedure. To arrest the progression of ischemia an additional endovascular procedure or an open surgery of femoral, popliteal and the crural arteries is necessary. The majority of these operations or procedures are reconstructive operations of the femoral, popliteal and the crural arteries. The effectiveness of the iliac artery PTA depends on the stage of lower limb ischemia. The need of an additional intervention is determined by the nature of lesion of the femoral arteries and the increase in ankle-brachial... [to full text] / Tyrimo tikslas – nustatyti klubo arterijų perkutaninės transliuminalinės angioplastikos veiksmingumą mažinant apatinių galūnių išemiją ir ištirti, kokios įtakos ši gydomoji procedūra turi galūnių amputacijos dažniui. Įvade išdėstomi tyrimo tikslai bei uždaviniai, pateikiama literatūros apžvalga, kurioje apibendrinamos pagrindinės su nagrinėjama tema susijusios problemos. Atskirame skyriuje aprašyta tyrimo metodika. Disertacijoje išnagrinėti 146 pacientų, kuriems atlikta klubo arterijų perkutaninė transliuminalinė angioplastika, gydymo rezultatai. Nustatyta, kad kriterijai angioplastikos veiksmingumui įvertinti – kulkšnies-žasto indekso pokytis, išemijos sumažėjimas pagal Fontaine’o galūnės išemijos stadijas. Taip pat nustatyta, kad klubo arterijos PTA pakankamas efektas ir papildomų intervencijų poreikis daugiausia išryškėja ankstyvuoju pooperaciniu laikotarpiu (iki 7 dienų po PTA), o PTA rezultatai laipsniškai blogėja per vienerius metus. Išemijos progresavimui sustabdyti reikalinga šlaunies, pakinklio ir blauzdos arterijų papildoma endovaskulinė arba atviroji operacija, dažniausiai – rekonstrukcinės arterijų operacija. Klubo arterijų angioplastikos veiksmingumas priklauso nuo išemijos stadijos. Papildomos intervencijos poreikį po PTA lemia šlaunies arterijų pažeidimo pobūdis, kulkšnies-žasto indekso pokytis mažiau negu 0,15. Bendras pacientų sergamumas kitomis ligomis pakankamos angioplastikos ir papildomų intervencijų grupėje buvo vienodas. Iš tirtų periferinių arterijų... [toliau žr. visą tekstą]

Cardiovascular disease (CVD) is a progressive disease that presents signs, such as abnormal thickening or stiffening of arteries, early in its preclinical stage, and screening tools such as carotid intima media thickness (CIMT) measurement and pulse wave velocity (PWV) assessment have the potential to identify individuals prior to the clinical manifestation of CVD. The purpose of this study was to determine the prevalence of preclinical atherosclerosis, as indicated by high CIMT and PWV values, in an adult population aged 40-70 years and free of diagnosed CVD using these screening tools. Secondarily, this study aimed to compare established CVD risk factors and other health parameters between those with elevated or normal arterial health values. Sixty subjects made 2 visits to the Ball State University Human Performance Laboratory. The first visit included basic anthropometric measurements as well as assessment of CIMT and PWV. After a one week objective physical activity assessment, subjects returned to the HPL for assessment of blood lipids and body composition via dual energy x-ray absorptiometry scan. Prevalence of preclinical atherosclerosis was calculated from the total sample as well as within both genders, and an independent samples t-test was conducted in order to identify significant differences in health characteristics between those in the normal and high groups. Abnormal CIMT or PWV values were present in 43% of study subjects; 30% and 18% of the test sample met the criteria for elevated CIMT and PWV, respectively. Significant differences existed between normal and high CIMT and PWV study groups for physical activity, body composition, and blood lipid profile variables. Comparisons within each gender revealed differences in health profile elements. Both the CIMT and PWV measurement techniques may be valuable additions for community CVD screenings, as certain health profile abnormalities may impact each marker of arterial health differently. Additional research is needed in order to determine the cost-effectiveness of these screening tools as a preventive health method. / School of Physical Education, Sport, and Exercise Science

Background: Cardiovascular disease (CVD) is becoming one of the leading causes of death in middle and low income countries, with ischaemic heart disease specifically being predicted to be the 4th and 5th causes respectively. The numerous risk factors for the development of CVD have been extensively researched; however, the same wealth of data is not available for the black South African population as there is for Caucasians. Although the same risk factors that are present in Caucasians have been seen to be present in the black South Africans, there are questions regarding the contributory roles of the individual risk factors, particularly within the context of urbanisation. The role of diet in CVD has been widely studied and it is known that with urbanisation there are dietary changes which are thought to add the development of CVD. With urbanisation, however, there are numerous other lifestyle changes taking place within a population, making it difficult to isolate and make conclusions of the individual role of diet. Added to this is the complex issue of assessing dietary intake. Assessing only nutrient or food intake does not give a holistic picture of dietary habits. The main aim of this study was to determine the association between dietary intake and CVD risk in black South Africans in the context of urbanisation. Methods: The first study that forms part of this thesis was a case-control study aimed at exploring the risk factor profile and clinical presentation of black South African patients with coronary artery disease (CAD). In this study clinical, biochemical and nutrient intakes were compared with a black South African control group that were matched for age and body composition. The second study to form part of this thesis aimed to relate the dietary intakes of the Prospective Urban and Rural Epidemiological (PURE) study population to CVD risk associated with urbanisation, by using both nutrient intake and predefined diet quality scores (DQS). The Healthy Diet Indicator (HDI) and the Deficiency and Excess Score were carefully selected from the large number of available scores and adapted as best as possible for the black South African population. The third study aimed to investigate the role of dietary intake by using nutrients as well as food group consumption patterns as a risk factor in urbanised black South African CAD patients. The dietary habits of the coronary artery disease (CAD) patients were compared to that of an apparently healthy reference group of volunteers selected from the PURE study population. This urbanised reference group was from a similar socio- demographic background and was selected according to their risk for CVD. The Reynolds Risk score which includes C-reactive protein as factor was used to stratify the PURE population into CVD risk categories, in order to select the reference group, which had a low risk (<5%) of developing CVD within the next 10 years. Dietary intake was assessed by comparing nutrient and food group intake (including the ultra-processed food group category). Results and discussion: Black South African CAD patients had increased levels of the same risk factors that are seen in Caucasians with insulin resistance and LDL size being particularly significant in their contribution. Apart from a lower vitamin C intake, no differences in dietary intake and physical activity were observed between the CAD and control group. When comparing the dietary intake of the rural and urban group, the urban group, who had an increased CVD risk, had higher intakes of macro- and micronutrients as well as higher DQS. The DQS must however be interpreted with caution, as when looking at the absolute intakes of individual components of the scores, the urban group was still deficient in a numerous vital micronutrients. A similar picture was seen in the third study, in that the CAD patients also consumed more saturated fatty acids and ultra-processed foods than the reference group, as well as more of the “protective” foods such as fruit and vegetables. However, although their dietary habits could be considered prudent, they were still inadequate in numerous important micronutrients. Conclusion and recommendation: This thesis therefore shows that there are two sides of the story regarding the role of diet in CVD in black South Africans. Although it is important to follow prudent dietary guidelines so as to control the intake of nutrients and foods known to play a role in the development of CVD, it is just as important to ensure adequate intake of the foods rich in micronutrients known to protect against CVD. Dietary advice and prevention programs should also focus on the adequacy aspect of the diet, such as increasing fruit and vegetable and low fat dairy intake, not only on the prudent diet aspect. Additionally, nutrient intake alone does not adequately explain the link between diet and CVD and additional analyses such food consumption patterns are required. / Thesis (PhD (Dietetics))--North-West University, Potchefstroom Campus, 2013

Background: Cardiovascular disease (CVD) is becoming one of the leading causes of death in middle and low income countries, with ischaemic heart disease specifically being predicted to be the 4th and 5th causes respectively. The numerous risk factors for the development of CVD have been extensively researched; however, the same wealth of data is not available for the black South African population as there is for Caucasians. Although the same risk factors that are present in Caucasians have been seen to be present in the black South Africans, there are questions regarding the contributory roles of the individual risk factors, particularly within the context of urbanisation. The role of diet in CVD has been widely studied and it is known that with urbanisation there are dietary changes which are thought to add the development of CVD. With urbanisation, however, there are numerous other lifestyle changes taking place within a population, making it difficult to isolate and make conclusions of the individual role of diet. Added to this is the complex issue of assessing dietary intake. Assessing only nutrient or food intake does not give a holistic picture of dietary habits. The main aim of this study was to determine the association between dietary intake and CVD risk in black South Africans in the context of urbanisation. Methods: The first study that forms part of this thesis was a case-control study aimed at exploring the risk factor profile and clinical presentation of black South African patients with coronary artery disease (CAD). In this study clinical, biochemical and nutrient intakes were compared with a black South African control group that were matched for age and body composition. The second study to form part of this thesis aimed to relate the dietary intakes of the Prospective Urban and Rural Epidemiological (PURE) study population to CVD risk associated with urbanisation, by using both nutrient intake and predefined diet quality scores (DQS). The Healthy Diet Indicator (HDI) and the Deficiency and Excess Score were carefully selected from the large number of available scores and adapted as best as possible for the black South African population. The third study aimed to investigate the role of dietary intake by using nutrients as well as food group consumption patterns as a risk factor in urbanised black South African CAD patients. The dietary habits of the coronary artery disease (CAD) patients were compared to that of an apparently healthy reference group of volunteers selected from the PURE study population. This urbanised reference group was from a similar socio- demographic background and was selected according to their risk for CVD. The Reynolds Risk score which includes C-reactive protein as factor was used to stratify the PURE population into CVD risk categories, in order to select the reference group, which had a low risk (<5%) of developing CVD within the next 10 years. Dietary intake was assessed by comparing nutrient and food group intake (including the ultra-processed food group category). Results and discussion: Black South African CAD patients had increased levels of the same risk factors that are seen in Caucasians with insulin resistance and LDL size being particularly significant in their contribution. Apart from a lower vitamin C intake, no differences in dietary intake and physical activity were observed between the CAD and control group. When comparing the dietary intake of the rural and urban group, the urban group, who had an increased CVD risk, had higher intakes of macro- and micronutrients as well as higher DQS. The DQS must however be interpreted with caution, as when looking at the absolute intakes of individual components of the scores, the urban group was still deficient in a numerous vital micronutrients. A similar picture was seen in the third study, in that the CAD patients also consumed more saturated fatty acids and ultra-processed foods than the reference group, as well as more of the “protective” foods such as fruit and vegetables. However, although their dietary habits could be considered prudent, they were still inadequate in numerous important micronutrients. Conclusion and recommendation: This thesis therefore shows that there are two sides of the story regarding the role of diet in CVD in black South Africans. Although it is important to follow prudent dietary guidelines so as to control the intake of nutrients and foods known to play a role in the development of CVD, it is just as important to ensure adequate intake of the foods rich in micronutrients known to protect against CVD. Dietary advice and prevention programs should also focus on the adequacy aspect of the diet, such as increasing fruit and vegetable and low fat dairy intake, not only on the prudent diet aspect. Additionally, nutrient intake alone does not adequately explain the link between diet and CVD and additional analyses such food consumption patterns are required. / Thesis (PhD (Dietetics))--North-West University, Potchefstroom Campus, 2013

Motivated by the physiological phenomena of collapse and flow limitation for a serial pulmonary artery stenosis, we investigated the three-dimensional influence of spatial configuration on the wall motion and hemodynamic. Our numerical study focused on the effect of two geometrical parameters: the relative distance and the angular orientation between the two stenoses. The collapse of a compliant arterial stenosis may cause flow choking, which would limit the flow reserve to major vital vascular beds such as the lungs, potentially leading to a lethal ventilation-perfusion mismatch. Flow through a stenotic vessel is known to produce flow separation downstream of the throat. The eccentricity of a stenosis leads to asymmetric flow where the high velocity jets impinge on the sidewall, thereby inducing significant dissipation. The additional viscous dissipation causes a higher pressure drop for a flow through a stenotic vessel, than in a straight compliant vessel. It is likely that some particular morphology would have a higher vulnerability to the fluid induced instability of buckling (divergence), under physiological pulsatile flow. It was found that fluid pressure distribution have substantial implication for the downstream wall motion, under conditions of strong coupling between nonlinear vessel geometries, and their corresponding asymmetric flow. The three-dimensional fluid structure interaction problem is solved numerically by a finite element method based on the Arbitrary Lagrangian Eulerian formulation, a natural approach to deal with the moving interface between the flow and vessel. The findings of this investigation reveal that the closeness between stenoses is a substantial indication of wall collapse at the downstream end. Moreover, the results suggest a close link between the initial angular orientation of the distal stenosis (i.e. the constriction direction) and the subsequent wall motion at the downstream end. For cases showing evidence of preferential direction of wall motion, it was found that the constricted side underwent greater cumulative displacement than the straight side, suggestive of significant wall collapse.

Systemic Lupus Erythematosus (SLE), a prototypic multi-organ autoimmune disease, is associated with a dramatically increased risk of coronary artery disease (CAD) manifesting as angina, myocardial infarction and sudden cardiac death. Traditional cardiac risk factors such as hypertension and hypercholesterolemia, measured at baseline in accordance with the Framingham model, only partially account for the increased risk of CAD in SLE. In this thesis, I have shown that blood pressure (BP), lipids and novel risk factors such as the inflammatory marker high-sensitivity C-reactive protein (hsCRP), take a dynamic course in SLE, with more than half of the variance in serial measurements over time occurring within rather than between individuals. This variability is due to changes in disease activity, treatment, accrual of other cardiac risk factors, and complications such as infection. I have demonstrated that by capturing cumulative exposure over time, ‘summary measures’ such as arithmetic mean and time-adjusted mean (AM) are better able to quantify CAD risk in patients with SLE than single-point-in-time measurements of risk factors. By incorporating ‘summary measures’ such as mean and AM into time-dependent covariate survival analysis models, I was able to quantify the magnitude of increase in CAD risk associated with increments in systolic and diastolic BP, and to demonstrate and quantify the association between several lipids / lipoproteins and CAD risk in SLE. Using this methodology, I was also able to demonstrate that despite marked variability over time, ‘summary measures’ of hsCRP are independently predictive of CAD risk among patients with SLE, highlighting the pivotal role of inflammation in atherosclerosis. Furthermore, I was able to determine lipid and hsCRP ‘cut-points’ that will aid clinicians in identifying a subgroup of patients with SLE who are at significantly increased cardiac risk.

Systemic Lupus Erythematosus (SLE), a prototypic multi-organ autoimmune disease, is associated with a dramatically increased risk of coronary artery disease (CAD) manifesting as angina, myocardial infarction and sudden cardiac death. Traditional cardiac risk factors such as hypertension and hypercholesterolemia, measured at baseline in accordance with the Framingham model, only partially account for the increased risk of CAD in SLE. In this thesis, I have shown that blood pressure (BP), lipids and novel risk factors such as the inflammatory marker high-sensitivity C-reactive protein (hsCRP), take a dynamic course in SLE, with more than half of the variance in serial measurements over time occurring within rather than between individuals. This variability is due to changes in disease activity, treatment, accrual of other cardiac risk factors, and complications such as infection. I have demonstrated that by capturing cumulative exposure over time, ‘summary measures’ such as arithmetic mean and time-adjusted mean (AM) are better able to quantify CAD risk in patients with SLE than single-point-in-time measurements of risk factors. By incorporating ‘summary measures’ such as mean and AM into time-dependent covariate survival analysis models, I was able to quantify the magnitude of increase in CAD risk associated with increments in systolic and diastolic BP, and to demonstrate and quantify the association between several lipids / lipoproteins and CAD risk in SLE. Using this methodology, I was also able to demonstrate that despite marked variability over time, ‘summary measures’ of hsCRP are independently predictive of CAD risk among patients with SLE, highlighting the pivotal role of inflammation in atherosclerosis. Furthermore, I was able to determine lipid and hsCRP ‘cut-points’ that will aid clinicians in identifying a subgroup of patients with SLE who are at significantly increased cardiac risk.