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Item Mathematical modelling of the cardiovascular system to study the effects of respiratory sinus arrhythmia and heart failure : this dissertation is submitted for the degree of Doctor of Philosophy, School of Natural and Computational Science, Massey University(Massey University, 2021) Noreen, ShumailaThis thesis presents the development of lumped parameter models of the cardiovascular system with a specific aim of simulating the system dynamics over a range of heart rates. The models contain several new modelling features that have been introduced progressively throughout the thesis starting with isolated models and continuing with closed loop models of the circulation. Specifically, the contraction of the cardiac chambers is modelled using a time-dependent muscle force with constant elasticity instead of time dependent elasticity. A new hypothesis about the mechanical contraction of the atria generates realistic pressure volume loops. The inter-ventricular interaction is modelled as well. Additionally, hysteresis is incorporated in the aortic valve to produce an end-systolic reverse (negative) flow. Most of the model parameters were taken from the literature and experimental data. Sensitivity analysis was performed on one of the models outputs by changing one parameter at a time; this analysis indicated that the total blood volume is the most influential parameter in the model. The developed models were used to study the effects of Respiratory Sinus Arrhythmia (RSA), variability in heart rate at the frequency of breathing. RSA is an indicator of good health but the mechanism that gives rise to RSA and its function are still debatable. Two potential sources of RSA were incorporated: periodic heart rate that mimics the central regulation of heart rate which originates in the brainstem, and periodic systemic veins resistance that mimics one possible effect of the pleural pressure which drives breathing. The effects of RSA on cardiac output were then studied. The simulations suggest that the mean cardiac output does not change significantly due to RSA at either low or high heart rates. Two types of heart failure were simulated using the new models by changing certain model parameters: systolic and diastolic. Both the systolic and diastolic heart failures caused an accumulation of blood in the lungs. The ejection fraction for diastolic heart failure remained within the normal physiological range while in the case of systolic heart failure the ejection fraction reduced rapidly. These results are consistent with physiological observations.Item PreAdolescent CardioMetabolic Associations and Correlates : PACMAC : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in School of Sport and Exercise at Massey University, Wellington, New Zealand(Massey University, 2018) Castro, NicholasCardiovascular disease is typically associated with adults; however, atherosclerosis often initiates during preadolescence and has been linked to cardiometabolic risk factors. Preceding cardiometabolic risk factors include lifestyle factors: body fatness, physical fitness, physical [in]activity, sedentary behaviour, nutrition, and sleep. No known study has comprehensively assessed simultaneous associations among lifestyle factors with cardiometabolic risk factors in preadolescent children. A multicentred cross-sectional study design was utilised to investigate lifestyle factor associations with cardiometabolic risk factors in a sample of 392 children aged 8 to 10 years. Participants were recruited from primary schools located in the Wellington, Canterbury, and Otago regions in New Zealand. Data collection was carried out over 5 days between 09:00 a.m. and 12:00 p.m. at each location. The first objective assessed the associations among physical fitness, physical [in]activity, sedentary behaviour, nutrition, and sleep with body fatness indicators (body fat percentage, fat mass index, body mass index, and waist-to-hip ratio). Results indicated nutrition independently associated with body fat percentage (p < 0.05), whereas cardiorespiratory fitness significantly associated with all four body fatness indicators (p < 0.05). The second objective assessed the associations among body fatness, physical fitness, physical [in]activity, sedentary behaviour, nutrition, and sleep with cardiometabolic factors (blood pressure, cholesterol, vascular, and carbohydrate-metabolic). Results indicated body fat percentage associated with the blood pressure factor (p < 0.05); sedentary minutes, social jetlag, and Fruit and Vegetables pattern associated with the cholesterol factor (all p < 0.05); sedentary minutes and Processed Food pattern associated with the vascular factor (both p < 0.05); and cardiovascular fitness (V̇O₂max) and handgrip strength associated with the carbohydrate-metabolic factor (both p < 0.001). Accordingly, body fatness, physical fitness, nutrition, and sleep all associated with at least one cardiometabolic factor. Cardiorespiratory fitness associated with cardiometabolic health and was the key finding in Objective 1; therefore, physical fitness may be the most important lifestyle factor. However, as nutrition, sleep, sedentary behaviour, and body fatness also associated with cardiometabolic health, it appears one specific lifestyle factor does not entirely explain cardiometabolic health in preadolescent children, and thus a multimodal approach for health is required for this population.Item Determining the validity and reproducibility of the Healthy Heart Food Index : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand(Massey University, 2019) Guy, HarrietBackground: Diet quality is associated with cardiovascular disease (CVD) risk, and the New Zealand (NZ) Heart Foundation has produced dietary guidelines aimed at reducing CVD risk for adult New Zealanders. At present, there is no valid and reproducible diet quality index for older adults living in NZ, which focuses on CVD risk. Aim: To develop and determine the construct validity and reproducibility of the Healthy Heart Food index (HHFI) for measuring dietary patterns in older adults living in New Zealand. Method: The HHFI was developed based upon NZ Heart Foundation Guidelines. To assess HHFI reproducibility, 298 community dwelling participants aged 65-74 years completed the HHFl twice approximately four-weeks apart. To validate the index, 142 of these participants completed a four-day food record (4DFR). Construct validity was explored using Spearman's correlation coefficients and linear contrast analysis of selected nutrients from the 4DFR. Spearman's correlation coefficients, Wilcoxon ranked-signed tests, cross-classification, the weighted kappa statistic, and a Bland-Altman plot were used to assess HHFl reproducibility. Results: Mean HHFl total scores were 693i10.8 and 68.9i11.1 from the first and second HHFl administrations respectively. These scores were positively correlated (r= 0.662, P<0.001) and cross-classification showed 55.4% of participants were categorised into the same fertile and 6.3% were grossly misclassified. The weighted kappa statistic was K: 0.43, indicating moderate agreement between HHFI total scores. For construct validity, iron (r= 0.201), vitamin C (r= 0.174), and niacin (r= 0.205) (all P<0.05), and protein (r= 0.277), polyunsaturated fatty acids (r= 0.236), dietary fibre (r= 0.307), vitamin (r= 0.205), folate (r= (1268), potassium (r= 0.246), magnesium (r= 0.300), phosphorus (r= 0.281), zinc (r= 0.276), and selenium (r= 0.222) (all P<0.01), were positively correlated with the HHFI total score. Saturated fat and cholesterol were negatively correlated (r= -0.097 and -0.035 respectively) with the HHFI total score, however this was a non-significant association (P>0.05). Linear contrast analysis showed a significant positive association between polyunsaturated fat, monounsaturated fat, dietary fibre, potassium, folate (P<0.05), vitamin E (P<0.01), and magnesium (P<0.005) and HHFI total scores. Conclusion: Moderate adherence to the HHFI was shown in this population sample. Results indicate the HHFI demonstrated construct validity and good reproducibility for assessing CvD-related diet quality in older adults living in New Zealand. Further research is needed to examine the predictive validity of this index in relation to CVD risk.Item Multidisciplinary, multiple risk factor cardiovascular disease primary prevention programme in community pharmacy : a feasibility study : a thesis presented in partial fulfilment of the requirements for the degree of MSc Programme in Nutrition & Dietetics, School of Sport, Exercise and Nutrition, Massey University, Albany, New Zealand(Massey University, 2020) Alsford, Dave PeterBackground: Community pharmacy cardiovascular disease (CVD) primary prevention interventions, led by pharmacists, are effective. However, the majority of these have targeted single CVD risk factors and most have not adequately assessed the impact of dietary and physical activity behaviour. A multidisciplinary and multi- risk factor approach that involves collaboration between dietitians (dietary and physical activity consultations) and pharmacists (pharmacological treatment) may provide additional risk reduction benefits for participants. Objective: To assess the feasibility of implementing a community pharmacy-based CVD primary prevention programme using a multidisciplinary approach to motivate lifestyle behaviour change in participants at risk of CVD. The primary outcome was change in estimated five-year CVD risk. Methods: A 16-week single cohort pre- and post-test study was undertaken in two community pharmacies with twelve participants aged 40-74 years who had risk factors associated with increased CVD. Participants received dietary and physical activity advice at baseline and every four weeks by a student dietitian as well as pharmacological management assessment at baseline, 16 weeks and as needed by a pharmacist. Biochemical (blood lipids, blood pressure, HbA1c) and anthropometric (body composition, weight, height, waist and hip circumference) measures were compared at baseline, eight and 16 weeks. Behavioural measures (diet, physical activity and medication use) were compared between baseline and 16 weeks. Results: Eleven participants (68±5.2 years) completed the programme. Significant reductions from baseline to 16 weeks were observed for mean systolic and diastolic blood pressure (-5.47, p = 0.04 and -4.06mmHg, p = 0.01 respectively) and mean total cholesterol reduced significantly from baseline to eight weeks, (-0.43mmol/L; p = 0.005) but not between baseline and 16 weeks. The average diet quality score significantly improved by 12.6% from 65.9 to 74.2 out of 100 during the intervention period (p = 0.007). Other CVD risk factor measures showed a trend towards improvement. Five-year CVD risk did not significantly improve. Conclusions: Results are comparable to existing literature on interventions to reduce CVD in the community pharmacy setting. Findings within this small cohort, particularly the improvements seen in diet, support the inclusion of dietitians for the primary prevention of CVD in community pharmacies. A larger scale, controlled study will help in determining the extent of efficacy with this approach.Item Pharmacokinetics of nitrate and nitrite following beetroot juice consumption : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand(Massey University, 2019) Jakubcik, Emily MargaretBackground: Nitrate (NO₃⁻) rich beetroot juice (BR) supplementation has been shown to improve cardiovascular function via reduction to nitrite (NO₂⁻) and thus the signalling molecule nitric oxide (NO). However, limited research exists for the role of inorganic NO₂⁻ contained within BR. Objective: To evaluate the individual effects of NO₃⁻ and NO₂⁻ consumed from BR on plasma [NO₃⁻]/[NO₂⁻] and various cardiovascular measures. Design: Eleven adults completed four trials; whereby they consumed 250 mL of BR containing one of the following; i) High-NO₃⁻ (572 mg NO₃⁻, 32 mg NO₂⁻); ii) Med-NO₃⁻/NO₂⁻ (280 mg NO₃⁻, 237 mg NO₂⁻); iii) Med-NO₂⁻ (43 mg NO₃⁻, 262 mg NO₂⁻); iv) Placebo (PL; 8 mg NO₃⁻, 5.8 mg NO₂⁻). Plasma [NO₃⁻]/[NO₂⁻], blood pressure (BP), heart rate (HR), mean arterial pressure (MAP), cardiac output (CO) and stroke volume (SV) were measured at baseline and every hour or second hour for 6 h post BR consumption. Outcomes: Ingestion of the high-NO₃⁻ and med-NO₃⁻/NO₂⁻ BR increased plasma [NO₂⁻] and [NO₃⁻] from 2 h, with both remaining elevated after 6h (p<0.05). Med-NO₂⁻ increased plasma [NO₃⁻] (p<0.05), but did not increase plasma [NO₂⁻] compared to PL (p=0.177). MAP was lower following the consumption of high-NO₃⁻ at 4 h and med-NO₂⁻ at 6 h (p<0.05). However, there were no differences in SBP, DBP, HR, CO and SV between trials. Conclusion: Inorganic NO₃⁻ consumption is the critical factor in elevating plasma [NO₃⁻] or [NO₂⁻], however, both NO₂⁻ and NO₃⁻ show potential to reduce MAP. The known reduction of SBP/DBP following NO₃⁻ supplementation was not observed, making it unclear if NO₂⁻ contributes to a reduction in SBP/DBP alongside NO₃⁻.Item Exploring the meaning of cardiovascular disease with Māori men : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Health Psychology at Massey University, Albany, New Zealand(Massey University, 2019) Lisipeki, SamanthaEthnic disparities in health outcomes are an ongoing concern in Aotearoa/New Zealand. These disparities are particularly pronounced between Māori and non-Māori, and are especially apparent for cardiovascular disease (CVD). Despite these well-known disparities, research into how the social determinants of health manifest in the context of Māori people’s everyday lives and experiences of CVD is limited. Using a narrative approach, this research documents Māori male patients’ experiences of CVD within the context of everyday life. Four Māori males who have experienced cardiovascular care were recruited through the Waikato District Health Board secondary prevention service. The patients and their whānau (family) who wished to participate were engaged in three separate semi-structured interviews which explored topics involving their CVD diagnosis, experiences of CVD, their steps to accessing care and experiences of care. Overall, the cases revealed three key findings. First, various factors work in concert to influence participant access to cardiac care, which extend beyond individual decision making (such as structures of everyday life and resources). Second, there is considerable diversity in participant life circumstances, which are related to their experiences of care and its outcomes. Third, CVD impacted the lives of my participants differently and contributed to varying levels of illness disruption to their life narratives. This study contributes to a growing body of knowledge for addressing disparities in health outcomes between Māori and non-Māori.Item Trials and fibrillations : the social context of the coronary experience : a thesis submitted in partial fulfillment [sic.] of the degree of Master of Arts in the Dept. of Sociology at Massey University(Massey University, 1984) Sanders, JackieThis thesis has two aims. It is intended that it will provide a detailed description of the experience of a heart attack from the perspective of those who have this illness. It is also intended that it will elaborate a model for undertaking inductive research and theory generation. This model takes as its point of departure the work of Glaser and Strauss (l967). It builds upon their works by attempting to develop a model that will allow for the generation of higher-order sociological concepts from the data gathered in the field. The method developed here has been labelled the "theoretical interpretation" of the research findings. It involves the application of other sociological concepts to the descriptive account of the data. In so doing, it is intended that the low-level descriptive concepts derived from the field-work will be integrated into the more general body of sociological theory. The sociological concepts which are applied to the research findings are the ideological perspective, and the notion of the alienation of self and body.Item Filipino women's health study : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Albany, New Zealand(Massey University, 2017) Norrish, LianaBackground: Western acculturation has been shown to be detrimental to health outcomes. Recently, more Filipinos are migrating to New Zealand, which may increase lifestyle-related chronic diseases. Furthermore, Filipino populations already have a higher incidence of chronic disease and less favourable health outcomes than their Western counterparts. Understanding their risk will assist development of public health initiatives which can be utilised to protect the health of the growing Filipino New Zealand migrant population. Aim: The aim of this study was to investigate the risk of developing type 2 diabetes mellitus and cardiovascular disease among recently immigrated Filipino women Method: 62 recently-immigrated Filipino women, aged 19-45, were recruited from Auckland, New Zealand. A health and demographic information questionnaire was completed. Anthropometric measurements (height, weight, and waist circumference) and blood pressure were measured. Both total and percent body fat were determined using dual energy X-ray absorptiometry. Fasting glucose, insulin, and lipids were measured. Physical activity data was monitored by accelerometers and two-day food diaries were completed. Homeostasis Model Assessment 2 was used to quantify insulin resistance. The 30-year Framingham Risk Score was used to classify participants into low-, medium-, or high-risk of developing cardiovascular disease. Prevalence of metabolic syndrome according to the modified National Cholesterol Education Programme criteria was determined. Results: Body mass index, waist circumference, and percent body fat were positively correlated with higher insulin resistance. Smokers had higher insulin resistance than non-smokers. However, 90% of participants had a low long-term risk of developing cardiovascular disease and 10% of participants met the metabolic syndrome criteria. This study was cross-sectional and provided used self-selection sampling. Conclusion: Anthropometric measures and smoking were associated with higher insulin resistance in participants. Participants with metabolic syndrome (10%) were at a greater risk of developing type 2 diabetes mellitus. This study highlights the risk of diabetes and cardiovascular disease development, and the need for further research, in this Filipino migrant population. These findings also create a platform for improving New Zealand health programmes by targeting appropriate risk factors to improve insulin sensitivity and reduce risk of developing diabetes, and will help to raise awareness in the Filipino community.Item An investigation into the link between vitamin D status, erectile dysfunction and cardiovascular risk factors in ageing men in New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Nutritional Science at Massey University, Palmerston North, New Zealand(Massey University, 2016) Quilter, Merrin LouiseBackground Cardiovascular disease (CVD) is the leading cause of death worldwide, particularly amongst ageing males. Prevention and/or early identification and effective intervention are essential in the fight against CVD. Erectile Dysfunction (ED) is a prevalent and multi-factorial condition that is now accepted to be an early marker of subclinical CVD: the common denominator is endothelial dysfunction. Both the enzymatic capability for bioactivation of Vitamin D and the vitamin D receptor (VDR) are expressed in endothelial cells and vitamin D may play a role in endothelial function. Vitamin D deficiency (serum 25-hydroxyvitamin D (25(OH)D) concentrations ˂50 nmol/L) is a worldwide pandemic and serum 25(OH)D levels ˂75 nmol/L may result in metabolic and vascular deterioration leading to endothelial dysfunction, ED and CVD. Assessment of erectile function can be used to identify otherwise asymptomatic men at high risk of developing clinical CVD, at a time when effective intervention may prevent, delay or reverse its progression. Vitamin D status may be associated with ED and CVD risk and could help improve erectile function and vascular health. Objectives The aim of this research was to investigate the postulated link between vitamin D status, ED, and CVD risk factors. The objectives were (1) to assess the prevalence of ED (using the 5-item International Index of Erectile Function (IIEF-5)) and its associated sociodemographic, lifestyle, and medical correlates in New Zealand (NZ) men aged 40-70 years; (2) to investigate the relationship between vitamin D status (serum 25(OH)D concentration), ED and other CVD risk factors in men aged 40-70 years living in the Manawatu region of NZ; and (3) to examine the impact of common VDR gene (VDR) polymorphisms on this relationship. Method Two thousand men aged 40-70 years were randomly selected from the NZ Electoral Roll and sent an anonymous postal survey designed to assess the prevalence of ED and its sociodemographic, lifestyle, and medical risk factors. Six hundred men aged 40-70 years living in the Manawatu region were randomly selected from the NZ Electoral Roll and invited to participate in an observational study designed to provide a comprehensive health profile of self-reported healthy men and investigate the relationship between vitamin D status, ED, and a range of CVD risk factors. Eligible participants (n=100) completed a comprehensive health assessment including a medical history, anthropometric and cardiovascular assessment, fasting blood sample, computer-based questionnaire, a submaximal fitness test and a handgrip iv strength test. Blood samples were assessed for four common VDR polymorphisms (rs11568820 (Cdx2), rs10735810 (FokI), rs1544410 (BsmI) and rs731236 (TaqI)) using polymerase chain reaction-high resolution amplicon melt (PCR-HRM) analysis. Results The survey showed 38.4% of respondents presented with ED (IIEF-5 ≤21). Older age, non-European ethnicity and current smoking were significant independent predictors of an increased risk of ED, while a high household income and regular vigorous physical activity (PA) were deemed protective. The observational study showed 30 men presented with ED and a further 37 men had <75 nmol/L 25(OH)D. There was a weak positive correlation between IIEF-5 scores and 25(OH)D levels (rs=0.238, p=0.017). Men with <75 nmol/L had lower IIEF-5 scores compared to men with ≥75 nmol/L 25(OH)D (22(7) vs. 24(3), p=0.001). Men with ED had lower 25(OH)D levels compared to men without ED (74.5(34) vs. 84.5(24), p=0.062). Every 1 nmol/L of 25(OH)D predicted a 2% decrease in the age-adjusted risk of ED (age-adjusted OR=0.98 [0.96-1.00], p=0.046). The PCR-HRM analysis showed that the Cdx2, FokI and BsmI polymorphisms were all significantly associated with an adverse cardiovascular risk profile. The Cdx2 G allele was associated with lower IIEF-5 scores compared to the A allele (23(4) vs. 24(2), p=0.008) and the GA and GG genotypes were predictors of an increased age-adjusted risk of ED (age-adjusted OR=18.78 [1.98-178.60], p=0.011 and 8.53 [1.00-72.73], p=0.050 respectively). However, Cdx2 was not found to modify the age-adjusted association between 25(OH)D levels and ED (multi-adjusted OR=0.97 [0.95-1.00], p=0.032). Conclusions These results suggest that over a third of NZ men aged 40-70 years suffer from ED and it is associated with sociodemographic, lifestyle and medical factors similar to CVD. Low serum 25(OH)D is associated with the presence and severity of ED in a self-reported healthy population. Common VDR polymorphisms are also associated with ED; however, they do not modify the association between serum 25(OH)D and ED. A randomised placebo-controlled human intervention trial is warranted to investigate whether improving vitamin D status in men with vitamin D deficiency and ED ameliorates symptoms and reduces the risk of CVD.Item The effect of a cardiac rehabilitation programme on carotid stiffness and haemodynamic properties of patients diagnosed with a transient ischaemic attack : a pilot study : compiled by Brandon Woolley for the degree of Master of Health Science in Sport and Exercise Science from Massey University, Wellington(Massey University, 2013) Woolley, BrandonArterial stiffness is associated with cardiovascular risk factors (e.g., hypertension, abnormal blood lipids and lipoproteins, physical inactivity and obesity) and the existence of atherosclerosis, and is identified as an independent risk factor for coronary artery disease and ischaemic stroke. The common carotid artery is the major conduit supplying blood to the brain is of particular interest. Research has demonstrated that interventions, which target the aforementioned risk factors, reduce the risk of occurring vascular events. The aims of this study were to 1) identify whether an 8-week cardiac rehabilitation programme reduces the stiffness of the common carotid artery, as determined by changes in arterial compliance, distensibility and stiffness index β, in transient ischaemic attack (TIA), and; 2) investigate the relationship between changes to arterial stiffness and haemodynamic properties of the common carotid artery. Eighteen male and female participants (mean ± SD; 65 ± 11 y, 1.72 ± 0.07 m, 85.6 ± 11.5 kg) recruited within a 14 day period following a TIA, volunteered to take part in the present study. Initial risk stratification assessments (i.e., cholesterol, glucose, ECG, etc) were completed prior to assessing arterial stiffness and haemodynamic properties. An ultrasound device was used to obtain arterial measures while participants were rested and in a supine position. Participants were then randomised to either an exercise (EX; 8-week intervention), or to a usual-care control (CON) condition. Identical vascular measures were obtained post-intervention. Results revealed a significant Test by Condition interaction for arterial compliance, distensibility and stiffness index β, and for compliance and distensibility following the 8-week exercise intervention (all P < 0.05). Post-hoc analysis demonstrated a significantly greater change in compliance and distensibility for the EX condition. No significant changes were observed in arterial haemodynamic properties or CAD risk stratification measures. The present study has demonstrated that exercise leads to improved vascular health, as determined by a decrease in arterial stiffness, thus potentially leading to a reduced risk of an ensuing or recurring cardio- or cerebrovascular event.