Thesis (Ph. D.)--University of Wisconsin--Madison, 1981. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 126-135).

Cardiac troponins are released into the circulation following myocardial injury with measurement of serum troponin concentration integral to the diagnosis of myocardial infarction. The next generation of high-sensitivity cardiac troponin assays have enhanced precision at very low concentrations and for the first time permit troponin concentrations to be reliably quantified outwith acute coronary syndromes. My aim was to evaluate the impact of more sensitive troponin assays on the diagnosis of myocardial infarction and to determine the potential for novel applications in stable cardiovascular diseases. In 2,929 consecutive hospitalised patients with myocardial injury I assessed the impact of implementing a contemporary sensitive troponin assay and a lower diagnostic threshold, on the incidence, management and outcome of patients with primary (type 1) and secondary (type 2) causes of myocardial infarction. Lowering the threshold improved outcomes in patients with type 1 myocardial infarction, but disproportionately increased the diagnosis of type 2 myocardial infarction, and identified a group of patients who remained at high-risk of death over the next 12 months. In 1,126 consecutive patients with suspected acute coronary syndrome I evaluated the impact of a high-sensitivity cardiac troponin I assay and sex-specific diagnostic thresholds on the diagnosis of myocardial infarction. Whilst having little effect in men, the use of sex-specific diagnostic thresholds would double the diagnosis of myocardial infarction in women, identifying those at increased risk of recurrent events. In a second cohort of 4,870 patients, I evaluated the optimal threshold to rule out myocardial infarction. The negative predictive value for myocardial infarction or cardiac death at 30 days was evaluated for a range of troponin concentrations. Troponin concentrations < 5 ng/L on presentation identified half of all patients with suspected acute myocardial infarction as low risk. Implementation of this assay and approach would markedly reduce hospital admissions and improve the diagnosis of myocardial infarction, particularly in women. High-sensitivity cardiac troponin assays may help us to manage patients with chronic cardiovascular diseases, such as aortic stenosis or stable angina pectoris. In patients with aortic stenosis, cardiac troponin was associated with an advanced hypertrophic response on electrocardiography and the presence of myocardial fibrosis on cardiac magnetic resonance imaging. Furthermore, cardiac troponin concentrations were a strong independent predictor of cardiovascular death or aortic valve replacement. In patients with stable angina, cardiac troponin was associated with transient ST-segment depression on ambulatory monitoring, suggesting that troponin concentrations may be modified by silent myocardial ischaemia. My findings suggest that high-sensitivity troponin assays have major potential to improve the assessment, treatment and outcome of patients with suspected acute coronary syndrome. The potential for cardiac troponins to improve risk stratification and monitoring of disease progression in patients with chronic cardiovascular disease now needs to be evaluated in prospective cohort studies.

The progression of genetically inherited cardiomyopathies from an altered protein structure to the clinical presentation of the disease is not well understood. One of the main roadblocks to mechanistic insight remains a lack of high-resolution structural information of multiprotein complexes within the cardiac sarcomere. One example is the tropomyosin (Tm) overlap region of the thin filament that is crucial for the function of the cardiac sarcomere. To address this central question, we devised coupled experimental and computational methods to characterize the baseline function and structure of the Tm overlap, as well as the effects that mutations causing divergent patterns of ventricular remodeling have on both structure and function.

No description available.

Troponin elevations are frequent during critical illness and associated with higher short-term mortality. Whether troponin elevations in that population independently confer a worse prognosis remains a matter of debate and how to manage patients with troponin elevations in the intensive care unit is unknown. Myocardial injury after noncardiac surgery is a well-defined entity, but can the same criteria be applied in patients who transition in the intensive care unit? Most patients present a troponin elevation early after coronary artery bypass surgery. How should a myocardial infarction be defined in these patients? This thesis comprises 7 chapters that inform these knowledge gaps. Chapter 1 is an introduction providing the rationale for conducting each of the included studies. Chapter 2 reports on the PROTROPIC pilot study evaluating the feasibility of a larger study to assess whether troponin elevations in critical illness independently predict mortality. Chapter 3 presents the use of secondary cardiovascular prevention medications and cardiac risk stratification in the PROTROPIC pilot study participants. Chapter 4 is a systematic review and meta-analysis of randomized controlled trials evaluating the efficacy and safety of statins in critically ill patients. Chapter 5 describes patients admitted to the intensive care unit after noncardiac surgery in the VISION cohort. This substudy also evaluates whether admission to the intensive care unit modifies the prognosis associated with myocardial injury after noncardiac surgery. Chapter 6 evaluates the prevalence and prognosis associated with different definitions of myocardial infarction after coronary artery bypass grafting using data from the CORONARY trial. Finally, Chapter 7 discusses the conclusion, limitation, and implications of the research presented in this PhD thesis. / Thesis / Doctor of Science (PhD)

An arginine (R) to a glycine (G) mutation at position 145 in the highly reserved inhibitory domain of cardiac troponin I (cTnI) is associated with hypertrophic cardiomyopathy (HCM), an autosomal dominant disease characterized by left ventricular hypertrophy. An arginine (R) to tryptophan (W) mutation at the same position in cTnI is associated with restrictive cardiomyopathy (RCM), a disease characterized by diastolic dysfunction with normal left ventricular size and normal systolic function. In this study we addressed the functional consequences of the human cardiac troponin I (hcTnI) HCM R145G mutation and hcTnI RCM R145W mutation in transgenic mice. Simultaneous measurements of the ATPase activity and force in skinned papillary fibers from hcTnI R145G transgenic mice (Tg-R145G) versus hcTnI wild type transgenic mice (Tg-WT) showed a significant decrease in the maximal Ca2+ activated force without changes in the maximal ATPase activity and an increase in the Ca2+ sensitivity by both ATPase activity and force development. No difference in the cross-bridge turnover rate was observed at the same level of cross-bridge attachment (activation state) showing that changes in Ca2+ sensitivity were not due to changes in cross-bridge kinetics. Energy cost calculations demonstrated higher energy consumption in Tg-R145G fibers compared to Tg-WT fibers. The addition of 3mM BDM at pCa 9.0 showed that there was approximately 2~4 percent of force generating cross-bridges attached in Tg-R145G fibers compared to less than 1.0 percent in Tg-WT fibers, suggesting the mutation impairs the ability of the cardiac troponin complex to fully inhibit cross-bridge attachment under relaxing conditions. Prolonged force and intracellular [Ca2+] transients in electrically stimulated intact papillary muscles were observed in Tg-R145G compared to Tg-WT. These results suggest that the phenotype of HCM is most likely caused by the compensatory mechanisms in the cardiovascular system which are activated by: 1) higher energy cost in the heart resulting from a significant decrease in average force per cross-bridge; 2) incomplete relaxation (diastolic dysfunction) caused by prolonged [Ca2+] and force transients; and 3) an inability of the cardiac TnI to completely inhibit activation at low levels of diastolic Ca2+ in Tg-R145G. Simultaneous measurements of the ATPase activity and force in transgenic skinned papillary fibers from hcTnI R145W transgenic mice (Tg-R145W) versus Tg-WT showed that there was a ~13 to ~16 percent increase in the maximal Ca2+ activated force and ATPase activity, respectively. The rate of dissociation of force generating cross-bridges (g) and energy cost (ATPase/force) was the same in all groups of fibers. These results suggest that the increase in force and ATPase activity is associated with an increase in the number of force generating cross-bridges attached at all activation levels. Additionally, there was a large increase in the Ca2+ sensitivity of force development and ATPase activity. In intact fibers, the mutation caused prolonged force and intracellular [Ca2+] transients, as expected due to the increased Ca2+ sensitivity (slower dissociation rate of Ca2+ from cTnC). The above cited results suggest that: 1) there would be an increase in resistance to ventricular filling during diastole resulting from the prolonged force and Ca2+ transients, especially at high heart rates; 2) there would be a decrease in ventricular filling (diastolic dysfunction); and 3) an increase in contractility during systole that would off-set the negative effect of a decrease in diastolic filling on ventricle stroke volume thus allowing the heart to maintain normal stroke volume despite the compromise in RCM (Tg-R145W) heart.

i) Human cardiac cDNA libraries were constructed and clones encoding human cardiac troponin I (cTnI) isolated. ii) Both the entire <i>cTNI</i> cDNA and a 5'-portion, were expressed in <i>Escherichia coli</i> as fusion products with β-galactosidase. The full-length cDNA was also expressed unfused. iii) The murine monoclonal antibody 29Mu is specific for human and baboon cTnI whereas the 31Mu antibody reacts with cTnI from a range of species. These antibodies might be useful in the imaging of necrotic cardiac tissue. In this study, 31Mu was found to bind to all prepared forms of cTnI antigen, in enzyme-linked immunosorbant assays (ELISAs) and, where tested, in Western blots. Thus, its epitope is localised towards the N-terminus of cTnI. 29Mu bound to the bacterially-produced unfused cTnI but not to the fusion polypeptides or crude bovine cTn. Its ability to bind to human cardiac extracts was related to the method of their preparation, indicating that the epitope of 29Mu shows greater conformational dependency than that of 31Mu. iv) cDNAs encoding the variable domains of 29Mu and 31Mu were cloned and chimaeric antibodies, comprising murine variable and human constant regions produced. Humanised antibodies, in which only the antigen-binding sites were of murine origin, were also produced. Such recombinant antibodies would be expected to exhibit reduced immunogenicity in man. v) Neither the chimaeric nor humanised antibody versions of 29Mu bound cTnI. Chimaerised 31Mu reacted with all forms of cTnI but did not show complete equivalence to 31Mu. An antibody containing the humanised 31 kappa chain and the chimaeric heavy chain was reactive to all forms cTnI in ELISAs but its efficiency of binding, relative to that of the chimaeric antibody, was dependent upon the antigen source. Humanised heavy chains were produced utilising two different human frameworks and the framework, showing closer homology to the 31Mu variable domain, supported antigen binding with fewer murine residue substitutions. However, both successful humanised 31 antibodies showed some cross-reactivity.

Background: Hyperthyroidism has substantial effects on the circulatory system. The cardiac biomarkers NT-proBNP and troponin I (cTNI) have proven useful in identifying cats with myocardial disease but have not been as extensively investigated in hyperthyroidism. Hypothesis: Plasma NT-proBNP and cTNI concentrations are higher in cats with primary cardiac disease than in cats with hyperthyroidism and higher in cats with hyperthyroidism than in healthy control cats. Animals: Twenty-three hyperthyroid cats, 19 cats with HCM without congestive heart failure, and 19 euthyroid, normotensive healthy cats eight years of age or older. Fourteen of the hyperthyroid cats were re-evaluated three months after administration of 131I. Methods: A complete history, physical examination, complete blood count, serum biochemistries, urinalysis, blood pressure measurement, serum T4 concentration, plasma concentrations of NT-proBNP and cTNI, and echocardiogram was prospectively obtained from each cat. Results: Hyperthyroid and HCM cats had plasma NT-proBNP and cTNI concentrations that were significantly greater than healthy older cats, but there was no significant difference between hyperthyroid and HCM cats with respect to concentration of either biomarker. In hyperthyroid cats that were re-evaluated three months after 131I treatment, plasma NT-proBNP and cTNI concentrations as well as ventricular wall thickness decreased. Conclusions and Clinical Relevance: Although there may be a role for NT-proBNP in monitoring the cardiac response to treatment of hyperthyroidism, neither NT-proBNP nor cTNI can be used to distinguish hyperthyroid cats from cats with HCM. Therefore, the thyroid status of older cats should be ascertained prior to interpreting results of cardiac biomarker testing. / Master of Science

Physical activity is a useful tool in the prevention of many diseases. Hospitalization after strenuous exercise from cardiac or noncardiac causes, even in young athletes without previous symptoms, can occur. These situations are not uncommon and e.g. after completing a half- marathon clinical symptoms suspicious from cardiac etiology can be present. Limitations of biomarkers used in daily clinical practice can lead to misinterpretation with additional consequences to the patient's outcome. Our goal was to describe changes of markers used in daily clinical practice after extreme physical activity and after exercise under laboratory conditions. We performed two studies in cooperation with Department of cardiology and Department of sports medicine. The goal of our first study was to examine high sensitivity troponin I (hsTnI), galectin-3, cystatin C, NGAL and ultrasensitive CRP (uCRP) after extremely long run during the competition in long distance running. The goal of our second study was to examine high- sensitivity troponin T (hsTnT) and hsTnI, creatinine and cystatin C, and urine albumin and NGAL after a standardized two-hour treadmill run under laboratory conditions and to find possible connection with echocardiographic, laboratory and other assessed parameters. The second goal of study under laboratory...

Chui Wai Leung. / Thesis (M.Sc.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 120-126). / List of tables and figures --- p.1 / Declaration --- p.6 / Acknowledgments --- p.7 / Summary --- p.8 / Chapter Chapter 1: --- Introduction --- p.10 / Chapter 1.1 --- Acute Myocardial Infarction (AMI) / Chapter 1.2 --- Diagnosis of AMI / Chapter 1.2.1 --- Clinical Signs / Chapter 1.2.2 --- Electrocardiogram (ECG) / Chapter 1.2.3 --- Cardiac enzymes / Chapter 1.3 --- "CKMB,a marker of choice" / Chapter 1.4 --- "Troponin-T, another candidate marker" / Chapter 1.5 --- Objectives / Chapter Chapter 2: --- Analytical evaluation of CKMB measurement by the four methods --- p.20 / Chapter 2.1 --- Analytical methods / Chapter 2.1.1 --- Assay for total creatine kinase / Chapter 2.1.2 --- Assay for CKMB / Chapter 2.1.2.1 --- CKMB mass concentration assay / Chapter 2.1.2.2 --- CKMB EEC & immunoinhibition activity assay / Chapter 2.1.2.3 --- CKMB activity concentration assay1 / Chapter 2.1.2.4 --- CKMB activity concentration assay2 / Chapter 2.2 --- Precision / Chapter 2.3 --- Accuracy / Chapter 2.4 --- Linearity / Chapter 2.5 --- Recovery / Chapter 2.6 --- Interference / Chapter 2.6.1 --- Effect of haemolysis / Chapter 2.6.2 --- Effect of turbidity / Chapter 2.6.3 --- Effect of bilirubin / Chapter 2.7 --- Stability / Chapter Chapter 3 : --- Correlation among the four methods of CKMB measurement --- p.61 / Chapter Chapter 4 : --- Establishment of reference ranges for the four methods of CKMB measurement --- p.71 / Chapter Chapter 5: --- Information on the Qualitative Troponin-T Rapid Assay® --- p.80 / Chapter Chapter 6 : --- Clinical Evaluation of CKMB and Troponin-T in detection of AMI --- p.82 / Chapter 6.1 --- Material and Methods / Chapter 6.1.1 --- Subjects / Chapter 6.1.2 --- Specimens / Chapter 6.1.3 --- Criteria for diagnosis / Chapter 6.1.4 --- Analytical methods / Chapter 6.1.5 --- Statistical methods / Chapter 6.2 --- Results / Chapter 6.3 --- Discussion / Chapter Chapter 7 : --- General Discussion --- p.105 / Appendix 1: study protocol sheet --- p.113 / Appendix 2: diagnostic criteria for a definite AMI --- p.115 / Appendix 3: criteria for exclusion of AMI --- p.117 / Appendix 4: enzyme criteria --- p.118 / References --- p.120