Dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of the Master of Science in Medicine, Johannesburg, 2013 / Cardiac disease is a major cause of morbidity and mortality in patients with chronic kidney disease (CKD). Accurate evaluation of cardiac function is therefore important but difficult with commonly used imaging modalities such as echocardiography being subject to variable load changes in haemodialysis.

Thesis (M.A.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Models of muscle relevant to the study of the active state have been reviewed. Some of the implications of the existing force-velocity equations have been examined preliminary to the presentation of a new method for determining the active state curve and the formulation of a general active state equation. It has been demonstrated, both theoretically and experimentally, that the intensity of the active state at any instant can be determined from a set of isometric myograms recorded rapidly but with different external compliances. The length of the muscle must be kept constant while these myograms are being recorded. From such sets of isometric myograms taken at 25uC and at different resting tensions, regression lines of developed tension against compliance were calculated at 10 msec intervals after the stimulus. The tension, independent of external compliance, was calculated from such regression lines. The extension of the series elastic component at any instant was determined according to the method of MacPherson (1953) while the compliance of the series elastic component was determined by dividing this extension by P t' the intensity of the active state at that instant. Substituting this compliance in the corresponding regression equation, a general equation Pt - Ptpt - a Lt = 0 (where P t is the intensity of the active state, pt is the isometric tension at zero external compliance, a is the regression coefficient and Lt is the extension of the series elastic component at time t after the stimulus) was developed. Pt was obtained by solving this equation. The active state curves determined according to this method rise much more gradually than those previously proposed. / 2031-01-01

Catheter ablation complex or fractionated atrial electrograms (CFAE) may improve outcomes for persistent AF. However, it is unclear whether CFAE are important in maintaining AF or whether targeting of CFAE can be refined based on electrogram morphology or knowledge of the remodelling process. A detailed classification of CFAE was described. Assessment of 100 CFAE by visual inspection in real time correlated well with detailed offline measurement. Targeting of different CFAE morphologies in 20 patients with persistent AF caused cycle length prolongation only with ablation of certain CFAE morphologies. Therefore, targeting CFAE is not simply atrial de-bulking, certain CFAE morphologies are more important for maintaining AF. A computer model was established to simulate LA wall stress using a 3D reconstruction of the chamber from CT imaging. Electrophysiologic data was acquired in 19 patients in persistent AF and compared to simulated wall stress data. Peaks in wall stress were associated with areas of low voltage suggestive of focal remodelling. CFAE were not associated with peaks in wall stress or areas of remodelling. Wall stress did not determine whether ablation of CFAE caused cycle length prolongation. Long term outcome of catheter ablation for AF was good with little late recurrence. Outcome for persistent AF was improved by targeting CFAE in addition to pulmonary vein isolation and may reduce late recurrence.

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Thesis (M.S.)--Boston University

No description available.

Mak Man Ting. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1997. / Includes bibliographical references (leaves 116-125). / ABSTRACT --- p.i / ACKNOWLEDGMENTS --- p.iv / TABLE OF CONTENTS --- p.v / LIST OF TABLES --- p.ix / LIST OF FIGURES --- p.x / Chapter CHAPTER1 --- INTRODUCTION --- p.1 / Chapter CHAPTER2 --- LITERATURE REVIEW / Chapter 2.1 --- General Review on Crustacean Circulatory System --- p.3 / Chapter 2.1.1 --- General anatomy and function --- p.3 / Chapter 2.1.2 --- Control mechanisms of cardiac function --- p.5 / Chapter 2.1.2.1 --- Intrinsic control --- p.6 / Chapter 2.1.2.2 --- Extrinsic control --- p.6 / Chapter 2.1.3 --- Ontogenic changes in cardiac function --- p.8 / Chapter 2.1.3.1 --- Change in heart rate during development --- p.8 / Chapter 2.1.3.2 --- Change from myogenic heart to neurogenic heart --- p.9 / Chapter 2.2 --- Effect of Temperature on Crustacean Cardiac Function --- p.10 / Chapter 2.2.1 --- General effect of temperature on crustaceans --- p.10 / Chapter 2.2.2 --- Effect of temperature on heart rate --- p.11 / Chapter 2.2.3 --- "Inter-relationship between heart rate, stroke volume and cardiac output" --- p.14 / Chapter 2.2.4 --- Control mechanisms on crustacean cardiac function in response to temperature change --- p.15 / Chapter 2.3 --- Effect of Salinity on Crustacean Cardiac Function --- p.18 / Chapter 2.3.1 --- General effect of salinity on crustaceans --- p.18 / Chapter 2.3.2 --- Effect of salinity on heart rate --- p.21 / Chapter 2.3.3 --- Effect of salinity on hemolymph flow distribution --- p.25 / Chapter CHAPTER3 --- CHANGES IN HEART RATE DURING DEVELOPMENT / Chapter 3.1 --- Introduction --- p.27 / Chapter 3.2 --- Materials and Methods --- p.29 / Chapter 3.3 --- Results --- p.31 / Chapter 3.4 --- Discussion --- p.34 / Chapter CHATPER4 --- EFFECT OF SALINITY ON HEART RATE OF METAPENAEUS ENSIS / Chapter 4.1 --- Introduction --- p.43 / Chapter 4.2 --- Materials and Methods --- p.45 / Chapter 4.3 --- Results --- p.48 / Chapter 4.4 --- Discussion --- p.51 / Chapter CHATPER5 --- EFFECT OF TEMPERATURE ON HEART RATE OF METAPENAEUS ENSIS / Chapter 5.1 --- Introduction --- p.58 / Chapter 5.2 --- Materials and Methods --- p.59 / Chapter 5.3 --- Results --- p.62 / Chapter 5.4 --- Discussion --- p.77 / Chapter CHAPTER6 --- DEVELOPMENT OF HEART INNERVATION IN METAPENAEUS ENSIS / Chapter 6.1 --- Introduction --- p.86 / Chapter 6.2 --- Materials and Methods --- p.87 / Chapter 6.3 --- Results --- p.89 / Chapter 6.4 --- Discussion --- p.109 / Chapter CHAPTER7 --- CONCLUSIONS --- p.112 / REFERENCES --- p.116

A ventricular septal defect occurring on its own is a congenital defect of the interventricular septum of the heart causing varying degrees of increased pulmonary blood flow and associated clinical symptoms. It may also occur in association with obstruction in the right ventricle resulting in diminished pulmonary blood flow. Very little is documented about the incidence of ventricular septal defects in South African children. The aim of this study was to briefly review the embryology and consider the normal anatomy of the interventricular septum. In addition, the clinical and surgical notes of all children that underwent surgical repair of ventricular septal defects (these included isolated ventricular septal defects, those with multiple ventricular septal defects, as well as those associated with tetralogy of Fallot and double chambered right ventricle) referred to the paediatric cardiothoracic unit at the Charlotte Maxeke Academic Hospital, from the Paediatric Cardiology units at the Charlotte Maxeke Academic Hospital, Chris Hani Baragwanath Academic Hospital and the Rahima Moosa Hospitals between 2001 and 2004, were analysed for the position, number of and size of ventricular septal defects. For this purpose, 11 cadaveric neonatal hearts were dissected while seven post-mortem specimens of the heart, four with isolated ventricular septal defects and three with tetralogy of Fallot were analysed. In addition, 50 cases of isolated ventricular septal defects, 42 cases with tetralogy of Fallot and eight cases with double chambered right ventricle were retrospectively reviewed. The membranous and the muscular septum made up the largest components of the interventricular septum in the normal neonatal hearts. A perimembranous ventricular septal defect was the most common type of defect diagnosed in these patients (the majority of the patients were Black children), 78% of cases with a single isolated ventricular septal defect, 90% in patients with tetralogy of Fallot, and 75% in the group with double chambered right ventricle. The average sizes of all perimembranous defects (from the echocardiogram) were classified as small, moderate or large. An additional interesting finding was prolapse of the right coronary cusp of the aortic valve into the isolated ventricular septal defect and occurred in 22% (11 out of 50) of patients. Aortic regurgitation occurred in association with prolapse of the right coronary cusp in 54.5% (5 out of 11) of cases. This prevalence in black patients is much higher than has been documented in White or Japanese children. Non-compaction of the left ventricle was seen in one post-mortem specimen in association with a perimembranous ventricular septal defect and dilated cardiomyopathy. This recently described abnormality is alluded to in the discussion. Attention is drawn to the abnormality known as double chambered right ventricle, where the size of the ventricular septal defect is variable and where the site of obstruction in the right ventricle is caused by muscle bundles lower than that seen in tetralogy of Fallot. Knowledge of ventricular septal defects found in South African children will help in the assessment and care of these patients with one of the most common congenital cardiac malformations.

Increases in internal dimensions of the chambers of the heart (cardiac dilatation), mediated by right shifts in cardiac chamber diastolic pressure-volume (P-V) relations, predict mortality in patients with established heart failure. However, the mechanisms responsible for the transition from concentric cardiac hypertrophy to cardiac dilatation are unclear. Recent evidence suggests that decreases in the cross-linked properties of myocardial collagen may increase the propensity of collagen to cleavage and hence reduce cardiac myocyte tethering, thus promoting cardiac dilatation. However, decreases in myocardial collagen cross-linking may also reduce myocardial stiffness, thus explaining right shifts in cardiac diastolic P-V relations. In the present dissertation I evaluated whether right shifts in diastolic P-V relations produced by chronic β-adrenoreceptor activation (isoproterenol, a β-adrenoreceptor agonist, 0.02 mg.kg-1.day) in spontaneously hypertensive rats (SHR) with compensated cardiac hypertrophy (12 months of age), can be explained by adverse chamber remodelling or alterations in the myocardial material properties of the heart. After 7 months of daily isoproterenol administration, SHR had marked right shifts in left ventricular (LV) diastolic P-V relations as determined in isolated, perfused hearts, with increases in the volume intercept of these relations, a change that translated into increases in LV cavity diameters (echocardiography). LV dilatation was associated with reductions in LV pump function (decreases in LV endocardial fractional shortening and the slope of the LV systolic P-V relation [LV E]). The reductions in pump function were attributed to the LV dilatation rather than to alterations in intrinsic myocardial contractile properties as LV midwall fractional shortening and myocardial systolic elastance (LV En) were unchanged. Although SHR not receiving isoproterenol had increases in the LV diastolic wall thickness-to-radius ratio, a change commensurate with compensatory concentric LV hypertrophy, LV wall thickness-to-radius ratio in SHR exposed to chronic β-adrenoreceptor activation was reduced to values similar to those noted in normotensive Wistar Kyoto (WKY) control rats, despite further increases in LV weight. SHR not receiving isoproterenol had a marked increase in myocardial stiffness (slope of the linearized LV diastolic stress-strain relationship) as compared to WKY rats, a change that was associated with an increased myocardial collagen of the cross-linked phenotype. Although SHR receiving daily isoproterenol had further increases in myocardial collagen, this did not translate into changes in LV diastolic myocardial stiffness, as the further increase in myocardial collagen was of the non cross-linked phenotype. However, through a susceptibility to digestion, this collagen phenotype could have contributed to LV dilatation. In conclusion, these data suggest that LV dilatation in SHR following chronic β-adrenoreceptor activation is attributed to adverse chamber remodelling rather than to alterations in myocardial material properties as indexed by diastolic stress-strain relations.

acase@tulane.edu / 1 / Annie Doucet