In patients with chronic kidney disease (CKD), overhydration, uremic toxins and left ventricular (LV) dyssynchrony are factors that may lead to LV dysfunction and conduction abnormalities and thus contribute to the high cardiac mortality. Colour tissue velocity imaging (TVI) allows a detailed quantitative analysis of cardiac function in CKD patients, opening new possibilities to evaluate longitudinal myocardial motion, rapid isovolumetric events, LV filling pressure and LV synchronicity. Aims: Using TVI technique: 1. To evaluate myocardial function disturbances and their relations to risk factors in CKD patients. 2. To assess LV synchronicity in HD patients, both at baseline and after HD, and 3. To study acute cardiac effects of HD and i.v. furosemide in HD patients. Methods: 40 predialysis CKD (stages I, II, III, IV and V) (Study II) and 59 HD (Studies I, III, IV and V) patients were studied. In both groups of patients LV function was evaluated using TVI, and in HD patients LV synchronicity was also assessed using tissue synchronization imaging (TSI). In HD patients the evaluations were performed before and after HD (Studies III and V) and i.v. furosemide infusion (Study IV). Results: 1. TVI detected: a) LV contraction disturbances in CKD patients with LVH and normal ejection fraction. b) An increase of LV contractility after HD. c) No changes in cardiac function induced by furosemide. 2. TSI detected the presence of LV dyssynchrony and its improvement after HD. 3. In CKD, cardiac dysfunction seemed to be related to high levels of PTH, phosphate and blood pressure. Conclusions: TVI is a sensitive tool for studies on cardiac function in CKD, allowing a detailed and accurate evaluation of disturbances in LV function. TVI also provides the possibility to follow the changes in LV function and synchronicity induced by different therapeutical interventions. The obtained information may contribute to a better management of CKD patients. / QC 20100809

More than 6 million people present to emergency departments (EDs) across the US annually with chief complaints of chest pain or other symptoms suggestive of acute myocardial infarction (AMI). Of the million who are diagnosed with AMI, 350,000 die during the acute phase. Accurate triage in the ED can reduce mortality and morbidity, yet accuracy rates are low and delays in patient care are high. The purpose of this study was to explore the relationship between (a) patient characteristics, registered nurse (RN) characteristics, symptom presentation, and accuracy of ED RN triage level designations and (b) delay of care of patients with symptoms suggestive of AMI. Constructs from Donabedian’s Structure-Process-Outcome model were used to guide this study. Descriptive correlational analyses were performed using retrospective triage data from electronic medical records. The sample of 286 patients with symptoms suggestive of AMI comprised primarily Caucasian, married, non-smokers, of mean age of 61 with no prior history of heart disease. The sample of triage nurses primarily comprised Caucasian females of mean age of 45 years with an associate’s degree in nursing and 11 years’ experience in the ED. RNs in the study had an accuracy rate of 54% in triage of patients with symptoms suggestive of AMI. The older RN was more accurate in triage level designation. Accuracy in triage level designations was significantly related to patient race/ethnicity. Logistic regression results suggested that accuracy of triage level designation was twice as likely (OR 2.07) to be accurate when the patient was non-Caucasian. The patient with chest pain reported at triage was also twice as likely (OR 2.55) to have an accurate triage than the patient with no chest pain reported at triage. Electrocardiogram (ECG) delay was significantly greater in the patient without chest pain and when the RN had more experience in ED nursing. Triage delay was significantly related to patient gender and race/ethnicity, with female patients and non-Caucasian patients experiencing greater delay. An increase in RN years of experience predicted greater delay in triage. Further studies are necessary to understand decisions at triage, expedite care, improve outcomes, and decrease deaths from AMI.

Cardiac output (Q) is an important determinant of the cardiovascular system‟s ability to meet the oxygen needs of the body. This dissertation addresses the non-invasive measurement of Q, in healthy children and those with heart and lung disease. 1) The correction factors for collision broadening, downstream difference and end tidal CO2 (PetCO2), used in the CO2 rebreathe (equilibrium) method, were evaluated. In lung disease, one is unable to assume a normal dead space to estimate arterial CO2 (PaCO2), and the use of any of these correction factors alone should be used with caution as they each exert a profound effect on the Q measurement. 2) A new equation to predict PaCO2 from PetCO2 in patients with CF was derived via multiple regression analysis, taking into account disease severity. 3) The validity and reliability of Q measures via the inert gas rebreathing technique (InnocorTM device) were evaluated. The highest intraclass correlation coefficients were attained during exercise (0.7-0.98), indicating excellent reliability of the device. Comparisons of Q measures from the InnocorTM (QInn) to the AMIS mass spectrometer system (QAmis) were made to assess validity. The bias (QInn-QAmis) and limits of agreement (±2SD) were 0.45 ± 1.9 L.min-1 and 0.27 ± 2.1 for children with congenital heart disease and healthy controls respectively, with no systematic differences between the two methods. 4) Assessment of cardiac output in Fontan patients demonstrated that an individualized, atrioventricular (AV) delay optimization was required. Moreover, there was a small but significant improvement in heart function with AV synchronized pacing (DDI) versus ventricular pacing (VVI), suggesting that further study with a larger sample of patients is warranted. The limitations and strengths of the measurement of non-invasive cardiac output in children, primarily via respiratory gas analysis, were delineated and recommendations were made for their use.

Treatment of cardiac diseases involves transplantation of donor hearts, since the damaged heart has limited self-regeneration potential. An alternative treatment option has emerged as engineered cardiac tissues, grown in vitro by cultivation of cardiac cells on biomaterials, have comparable properties to native myocardium and can be implanted for cardiac repair. Major current limitations are a viable cell source and adequate vascularization to support cell survival. In this thesis, two proangiogenic biomaterials, a scaffold and a hydrogel, were developed to achieve vascularization in vitro and in vivo for cardiac repair. Scaffold patches are suitable for repairing congestive heart failure or congenital malformations, while injectable biomaterials allow minimally-invasive treatment post-myocardial infarction (MI). In the first aim, a collagen scaffold with covalently immobilized vascular endothelial growth factor (VEGF) was developed, and improved cell mobilization, survival and proliferation when used for free wall repair in adult rats. This increased angiogenesis, which aided in retaining the biomaterial size to allow tissue growth. In the second aim, a collagen-chitosan hydrogel with encapsulated thymosin β4 (Tβ4) was developed to 1) recruit cells from the heart epicardium for repair post-MI in vivo, and 2) guide capillary outgrowths from arteries and veins to form oriented capillary structure for in vitro cardiac tissue engineering. Results showed that the encapsulation of Tβ4 into collagen-chitosan hydrogels led to cell outgrowths from rat or mouse cardiac explants in vitro. A portion of the recruited cells were CD31-positive endothelial cells (ECs) that formed tubes. The hydrogel was injected in vivo to increase vascularization and number of cardiomyocytes within the infarct area post-MI, which improved left ventricular wall thickness. Tβ4-hydrogel also promoted the outgrowth of capillaries from vascular explants that followed the direction of the hydrogel-coated grooves of a micropatterned polydimethylsiloxane (PDMS) substrate. These capillary outgrowths eventually formed a vascular bed for engineering vascularized cardiac tissues. This thesis presents two bioinstructive biomaterials with sustained and localized delivery of angiogenic molecules to be used for in situ cardiac repair based on improved vascularization. The use of cell-free bioactive materials overcomes limitations of cell isolation and expansion as required for cell therapies or implantation of engineered tissues.

Chronic iron overload (CIO) in patients leads to a cardiomyopathy characterized by conduction defects, including bradyarrhythmias. Using a murine model of CIO, we explored the effects of iron loading on the electrophyisology of the heart. Telemetric heart rate was reduced in conscious CIO mice compared to controls. Similarly, heart rates were depressed in both isolated CIO hearts and CIO mice following autonomic blockade, suggesting an intrinsic impairment of the SA node (SAN). Indeed, spontaneous action potential frequency was reduced in CIO SAN myocytes. The depressed pacing rate in CIO SAN myocytes was linked to reduced L-type Ca2+ current (ICa,L) density and a rightward shift in ICa,L activation, suggesting a selective reduction in α1D-mediated ICa,L. Western blot analysis demonstrates that the α1D isoform was reduced by ~ 89% in CIO atrial tissue. Therefore, the conduction defects under conditions of CIO are due to reductions in Cav1.3 channel expression in atrial tissue.

Coronary Artery Bypass Grafting (CABG) is an effective and invasive cardiac surgery to salvage blocked coronary artery. Cardiopulmonary bypass (CPB) is usually applied to support circulation during temporary cardiac arrest. Studies have demonstrated that cardiac injury, inflammation, and oxidative stress could be induced during CABG with CPB. We conducted two studies to investigate the release of cardiac biochemical markers and inflammatory response as well as to compare the effect of different coating biomaterial of CPB on the induction of inflammation and oxidative stress during CPB. We investigated the release patterns and the serum levels of cardiac markers as well as inflammatory markers in patients undergoing elective CABG at different time points after initiation of CPB. In this study, we demonstrated that cardiac markers such as creatine kinase isoenzyme MB (CK-MB), and cardiac troponin I (cTnI) and inflammatory markers such as tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and high sensitivity C-reactive protein (hsCRP) were highly elevated after CPB. Moreover, we confirmed that cTnI is still a better biochemical marker for cardiac injury than others following CABG with CPB. Other nonspecific but highly sensitive markers such as lactate dehydrogenase (LDH), lactate, TNF-alpha, IL-6, and hsCRP could be potential surrogate markers for evaluation of cardiac injury following CPB. Based on these findings, we conducted a further investigation to demonstrate our hypothesis that different biocompatible materials used in CPB may affect the inflammation and oxidative stress differently. Biocompatible materials are thinly coated on CPB tubes to provide similar environment like endothelial cells during cardiac surgery. There are several biocompatible materials available in the market. Each of them has unique characteristics. Inflammatory response is one of the bodys fundamental defense mechanisms against foreign invaders. However, inappropriate or excessive response can lead to harmful, potentially life-threatening consequences due to severe inflammatory tissue destruction. CPB-induced inflammatory response can be one of the factors, which can affect surgical outcomes. Depending on the presence of different biocompatible materials in CPB circuits, the degree of immunoreactions can be varied. In this study, we analyzed hsCRP, an acute phase protein, and tau protein, a marker of neurocognitive deficiency. Furthermore we analyzed inflammatory cytokines including TNF-alpha, IL-6, IL-10, and interferon-gamma (IFN-gamma) to evaluate the levels of inflammation. Serum levels of oxidized nitric oxide as a marker of oxidative stress were also assessed. We demonstrated that different biocompatible material has different impacts on inflammation and oxidative stress. In the aspect of anti-inflammation, heparin-coated biocompatible material is better than others whereas surface-modifying additives biocompatible material is worse than others. Overall, different coating biomaterial of CPB results in various inflammatory response. In terms of oxidative stress, we did not observe significant difference between different biomaterial-coated CPB.

No description available.

Cardiac output (Q) is an important determinant of the cardiovascular system‟s ability to meet the oxygen needs of the body. This dissertation addresses the non-invasive measurement of Q, in healthy children and those with heart and lung disease. 1) The correction factors for collision broadening, downstream difference and end tidal CO2 (PetCO2), used in the CO2 rebreathe (equilibrium) method, were evaluated. In lung disease, one is unable to assume a normal dead space to estimate arterial CO2 (PaCO2), and the use of any of these correction factors alone should be used with caution as they each exert a profound effect on the Q measurement. 2) A new equation to predict PaCO2 from PetCO2 in patients with CF was derived via multiple regression analysis, taking into account disease severity. 3) The validity and reliability of Q measures via the inert gas rebreathing technique (InnocorTM device) were evaluated. The highest intraclass correlation coefficients were attained during exercise (0.7-0.98), indicating excellent reliability of the device. Comparisons of Q measures from the InnocorTM (QInn) to the AMIS mass spectrometer system (QAmis) were made to assess validity. The bias (QInn-QAmis) and limits of agreement (±2SD) were 0.45 ± 1.9 L.min-1 and 0.27 ± 2.1 for children with congenital heart disease and healthy controls respectively, with no systematic differences between the two methods. 4) Assessment of cardiac output in Fontan patients demonstrated that an individualized, atrioventricular (AV) delay optimization was required. Moreover, there was a small but significant improvement in heart function with AV synchronized pacing (DDI) versus ventricular pacing (VVI), suggesting that further study with a larger sample of patients is warranted. The limitations and strengths of the measurement of non-invasive cardiac output in children, primarily via respiratory gas analysis, were delineated and recommendations were made for their use.

Chronic iron overload (CIO) in patients leads to a cardiomyopathy characterized by conduction defects, including bradyarrhythmias. Using a murine model of CIO, we explored the effects of iron loading on the electrophyisology of the heart. Telemetric heart rate was reduced in conscious CIO mice compared to controls. Similarly, heart rates were depressed in both isolated CIO hearts and CIO mice following autonomic blockade, suggesting an intrinsic impairment of the SA node (SAN). Indeed, spontaneous action potential frequency was reduced in CIO SAN myocytes. The depressed pacing rate in CIO SAN myocytes was linked to reduced L-type Ca2+ current (ICa,L) density and a rightward shift in ICa,L activation, suggesting a selective reduction in α1D-mediated ICa,L. Western blot analysis demonstrates that the α1D isoform was reduced by ~ 89% in CIO atrial tissue. Therefore, the conduction defects under conditions of CIO are due to reductions in Cav1.3 channel expression in atrial tissue.

The incidence of cardiovascular disease has reached epidemic proportions in North America. Specifically, myocardial infarctions (MI) are a major contributor to heart failure which greatly influences morbidity and mortality rates in developed nations. In the post-MI heart, cardiac fibroblasts migrate to the damaged area, convert to myofibroblasts and contribute to infarct scar contraction. As well, cardiac myofibroblasts are hypersynthetic for matrix components eg, collagen, and de novo production of fibrillar collagens lessens the chance for acute scar rupture. TGF-1 is important in the initiation of cardiac healing and fibrosis. Canonical TGF-1 signaling occurs with the activation of receptor-operated Smads (R-Smads) including Smad3. The current study addresses the question of whether Smad3 and/or myocardin influence myofibroblast contractility. We believe that myocardin is a Smad3 binding partner and cofactor and thus contributes to Smad associated healing and fibrotic events in the heart. In mesenchyme-derived cells, myocardin exists as a nuclear protein and is a cardiac and smooth muscle specific transcriptional coactivator of serum response factor (SRF). This transcription factor has been shown to bind to Smad3 in COS-7 cells (a green monkey kidney fibroblast-like cell line) and we suggest that it may contribute to fibroproliferative events. Precisely how Smad3/myocardin facilitates post-MI wound healing and/or contributes to inappropriate post-MI fibrosis is unknown. Very little work has been done to address myocardin expression in cardiac ventricular myofibroblasts. While a number of previous studies address TGF-β/Smad signaling in cardiac myofibroblasts, none have addressed the effects of overexpressed Smad3 on cellular contractility and collagen secretion. As Smad3 and its endogenous inhibitor Smad eg, I-Smad7, contribute significantly to TGF-β signaling in myofibroblasts, we rationalize that they must be important in the regulation of many fibroproliferative processes. Our goals were first to measure/determine myocardin expression in primary ventricular myofibroblasts; second, to explore a putative interaction between Smad3 and myocardin; third to examine a possible link between TGF-β1 stimulation, myocardin and Smad3. Finally, we sought to examine the effect of overexpressed Smad3, Smad7 and myocardin on contractility and collagen production. These experiments were conducted by using RT-PCR, co-immunoprecipitation, adenoviral overexpression of Smad3, Smad7 and myocardin, Western blot analysis, collagen gel deformation assays (contractility studies) and finally, Pro-collagen 1 N-terminal Peptide (P1NP) secretion as a measure of mature collagen production. We document the novel expression of myocardin in ventricular myofibroblasts and provide evidence that myocardin may serve as a Smad3 cofactor in cardiac myofibroblasts. Further, myocardin overexpression is linked to increased contractility in myofibroblasts compared to LacZ infected controls, and that TGF-β1 acutely stimulated myocardin expression followed by a dramatic reduction 1 hour thereafter. Overexpressed Smad3 alone led to increased contractility in primary ventricular myofibroblasts. Thus the effect of increasing myocardin expression had a comparable effect to that of increased Smad3 alone with this endpoint. Finally, overexpression of both Smad3 and myocardin in the presence of TGF-β1 led to an additive stimulation of contractility in cells when compared to the effect of TGF-β1 stimulation alone. Overexpressed Smad7 alone was associated with decreased secretion of type I collagen when compared to the control; when cells overexpressing Smad7 are stimulated with TGF-β1, collagen secretion is dramatically reduced when compared to cells treated with TGF-β1. In an addition series of experiments we addressed reverse mode NCX1 function as a means of Ca2+ entry to the cytosol of myofibroblasts upon their excitation. We have previously shown the stimulatory effect of TGF-β1 on myofibroblast contractility, and we now report that overexpression of Smad3 alone led to increased mRNA expression of NCX1. Thus it is possible that TGF-β1 signaling via Smad3 may influence Ca2+ movements and thus contractile performance in ventricular myofibroblasts. / May 2008