ORCID Profile
0000-0002-8244-8655
Current Organisations
University of Adelaide
,
TheUniversity of Adelaide
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Publisher: MDPI AG
Date: 10-07-2023
Abstract: Until recently, it has been generally held that stable angina pectoris (SAP) primarily reflects the presence of epicardial coronary artery stenoses due to atheromatous plaque(s), while acute myocardial infarction (AMI) results from thrombus formation on ruptured plaques. This concept is now challenged, especially by results of the ORBITA and ISCHEMIA trials, which showed that angioplasty/stenting does not substantially relieve SAP symptoms or prevent AMI or death in such patients. These disappointing outcomes serve to redirect attention towards anomalies of small coronary physiology. Recent studies suggest that coronary microvasculature is often both structurally and physiologically abnormal irrespective of the presence or absence of large coronary artery stenoses. Structural remodelling of the coronary microvasculature appears to be induced primarily by inflammation initiated by mast cell, platelet, and neutrophil activation, leading to erosion of the endothelial glycocalyx. This leads to the disruption of laminar flow and the facilitation of endothelial platelet interaction. Glycocalyx shedding has been implicated in the pathophysiology of coronary artery spasm, cardiovascular ageing, AMI, and viral vasculitis. Physiological dysfunction is closely linked to structural remodelling and occurs in most patients with myocardial ischemia, irrespective of the presence or absence of large-vessel stenoses. Dysfunction includes the impairment of platelet and vascular responsiveness to autocidal coronary vasodilators, such as nitric oxide, prostacyclin, and hydrogen sulphide, and predisposes both to coronary vasoconstriction and to a propensity for microthrombus formation. These findings emphasise the need for new directions in medical therapeutics for patients with SAP, as well as a wide range of other cardiovascular disorders.
Publisher: Ovid Technologies (Wolters Kluwer Health)
Date: 03-2014
Publisher: Elsevier BV
Date: 02-2014
Publisher: Springer Science and Business Media LLC
Date: 08-2014
DOI: 10.1007/S10557-014-6538-5
Abstract: The thioredoxin system, which consists of thioredoxin (Trx), nicotinamide adenine dinucleotide phosphate (NADPH) and thioredoxin reductase (TrxR), has emerged as a major anti-oxidant involved in the maintenance of cellular physiology and survival. Dysregulation in this system has been associated with metabolic, cardiovascular, and malignant disorders. Thioredoxin-interacting protein (TXNIP), also known as vitamin D-upregulated protein or thioredoxin-binding-protein-2, functions as a physiological inhibitor of Trx, and pathological suppression of Trx by TXNIP has been demonstrated in diabetes and cardiovascular diseases. Furthermore, TXNIP effects are partially Trx-independent these include direct activation of inflammation and inhibition of glucose uptake. Many of the effects of TXNIP are initiated by its dissociation from intra-nuclear binding with Trx or other SH-containing proteins: these effects include its migration to cytoplasm, modulating stress responses in mitochondria and endoplasmic reticulum, and also potentially activating apoptotic pathways. TXNIP also interacts with the nitric oxide (NO) signaling system, with apparent suppression of NO effect. TXNIP production is modulated by redox stress, glucose levels, hypoxia and several inflammatory activators. In recent studies, it has been shown that therapeutic agents including insulin, metformin, angiotensin converting enzyme inhibitors and calcium channel blockers reduce TXNIP expression, although it is uncertain to what extent TXNIP suppression contributes to their clinical efficacy. This review addresses the role of TXNIP in health and in cardiovascular and metabolic disorders. Finally, the potential advantages (and disadvantages) of pharmacological suppression of TXNIP in cardiovascular disease and diabetes are summarized.
Publisher: Elsevier BV
Date: 05-2014
Publisher: Elsevier BV
Date: 11-2011
DOI: 10.1016/J.AMJCARD.2011.06.047
Abstract: Takotsubo cardiomyopathy (TTC) is characterized by reversible left ventricular (LV) systolic dysfunction independent of fixed coronary disease or coronary spastic pathogenesis. A number of investigators have documented marked elevation of natriuretic peptide levels at presentation in such patients. We sought to determine the pattern, extent, and determinants of the release of N-terminal pro-B type natriuretic peptide/B type natriuretic peptide (NT-proBNP/BNP) in patients with TTC. We evaluated NT-proBNP/BNP release acutely and during the first 3 months in 56 patients with TTC (96% women, mean age 69 ± 11 years). The peak plasma NT-proBNP levels were compared to the pulmonary capillary wedge pressure and measures of regional and global LV systolic dysfunction (systolic wall stress, wall motion score index, and LV ejection fraction) as potential determinants of NT-proBNP/BNP release. In patients with TTC, the plasma concentrations of NT-proBNP (median 4,382 pg/ml, interquartile range 2,440 to 9,019) and BNP (median 617 pg/ml, interquartile range 426 to 1,026) were substantially elevated and increased significantly during the first 24 hours after the onset of symptoms (p = 0.001), with slow and incomplete resolution during the 3 months thereafter. The peak NT-proBNP levels exhibited no significant correlation with either pulmonary capillary wedge pressure or systolic wall stress. However, the peak NT-proBNP level correlated significantly with the simultaneous plasma normetanephrine concentrations (r = 0.53, p = 0.001) and the extent of impairment of LV systolic function, as measured by the wall motion score index (r = 0.37, p = 0.008) and LV ejection fraction (r = -0.39, p = 0.008). In conclusion, TTC is associated with marked and persistent elevation of NT-proBNP/BNP levels, which correlated with both the extent of catecholamine increase and the severity of LV systolic dysfunction.
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.HLC.2014.06.010
Abstract: Takotsubo cardiomyopathy (TTC) is often associated with hypotension and shock. However, development of hypotension/shock in TTC is not closely related to extent of left ventricular (LV) hypokinesis. We sought to determine whether additional right ventricular (RV) involvement in TTC might contribute to hypotension and shock development and thus to prolonged hospital stay (PHS). We evaluated 102 consecutive TTC patients with acute transthoracic echocardiography (TTE) to detect RV hypokinesis. Correlates of hypotension, shock and PHS were identified by univariate and multivariate analyses. Of the 102 patients evaluated, 33% had RV hypokinesis but only 9% had extensive RV involvement. Within the first 24 hours of admission, severe hypotension (systolic blood pressure (SBP) ≤ 90 mmHg) occurred in 21% of the patients and shock (hypotension + peripheral organ hypo-perfusion) in 16.6% of cases. RV involvement was a univariate but not a multivariate correlate of either hypotension or shock and did not result in PHS. On the other hand, RV involvement predicted more extensive LV hypokinesis and LV systolic dysfunction. In TTC, RV hypokinesis occurs in approximately 33% of cases and correlates with more severe LV wall motion abnormality but not with development of hypotension or shock. These data therefore reinforce previous findings that hypotension/shock in TTC are not purely by impaired cardiac output.
Publisher: BMJ
Date: 16-04-2014
DOI: 10.1136/HEARTJNL-2014-305509
Abstract: Bicuspid aortic valve (BAV) is associated with increased risk of valvular degeneration and ascending aortic aneurysm formation and rupture. We sought to evaluate the roles of endothelial dysfunction and inflammatory activation in modulating these processes. We performed a case-control study of patients with BAV together with a multivariate analysis within the BAV group to identify factors associated with: development of significant valvular disease dilatation of the ascending aorta differential valve relative to aortic disease. Endothelial function of patients and controls was evaluated via flow-mediated dilatation (FMD) and plasma concentrations of asymmetric dimethylarginine (ADMA). Correlations with inflammatory markers and endothelial progenitor cell counts were also examined. Morphological and physiological assessment of the valve and ascending aorta was performed with transthoracic echocardiography and MRI. Patients with BAV (n=43) and controls (n=25) were matched for age and gender. FMD was significantly lower in patients than controls (7.85±3.48% vs 11.58±3.98%, p=0.001), and these differences were age-independent. Within the BAV cohort, multivariate correlates of peak aortic valve velocity were plasma concentrations of ADMA and myeloperoxidase (MPO) (both p<0.01), while increasing age was an independent correlate of ascending aortic diameter (p<0.05). Furthermore, both low FMD and inflammatory activation were multivariate correlates of selectivity for valvular disease. BAV is associated with endothelial dysfunction. The extent of inflammatory activation (specifically MPO release) and that of endothelial dysfunction impact primarily on integrity of the valve rather than aortic structure.
Publisher: Wiley
Date: 12-04-2013
DOI: 10.1002/CLC.22129
Publisher: Springer Science and Business Media LLC
Date: 07-08-2013
DOI: 10.1007/S10557-013-6481-X
Abstract: Little information is available concerning the mechanism(s) underlying Takotsubo cardiomyopathy (TTC), other than evidence of associated catecholamine secretion. Given the known effects of catecholamines on endothelial function, we tested the hypothesis that TTC might also be associated with impairment of nitric oxide (NO) signaling. We now report an evaluation of NO signaling in TTC patients (vs. aged-matched controls) in relation to (a) severity of the acute attack and (b) rate of recovery. In 56 patients with TTC, we utilized (1) platelet responsiveness to NO and (2) plasma levels of asymmetric dimethylarginine (ADMA) as indices of integrity of the cyclic guanosine monophosphate (cGMP) pathway. Additionally, endothelial progenitor cell (EPC) counts, which are partially NO-dependent, were evaluated. These parameters were measured at the time of diagnosis and 3 months thereafter, and compared with an aging female cohort (n = 81). The data suggested that both NO generation and effect were accentuated in TTC patients: ADMA concentrations were lower (p = 0.003), and responsiveness to NO substantially greater (p = 0.0001) than in controls both acutely and after 3 months. Markers of severity of TTC attacks directly correlated with NO responsiveness, while extent of recovery at 3 months varied inversely with ADMA concentrations. TTC is associated with intensification of NO signaling relative to that in normal age-matched females. Our data are consistent with this intensified signal's potential contribution to the extent of initial myocardial injury, but conversely to accelerated recovery.
Publisher: Elsevier BV
Date: 04-2012
DOI: 10.1016/J.HLC.2011.12.004
Abstract: Tako-Tsubo cardiomyopathy (TTC) occurs particularly in post-menopausal women, being precipitated in many cases by severe emotional stress. We describe six patients in whom TTC occurred in association with therapeutic ingestion or overdose of the serotonin/noradrenaline reuptake inhibitor venlafaxine, or its metabolite desvenlafaxine. Importantly, two of the six cases were not post-menopausal women. An increased risk of TTC may account for some of the reported cardiovascular adverse effects of venlafaxine and similar agents.
Publisher: Informa UK Limited
Date: 02-2012
DOI: 10.1586/ERC.11.190
Abstract: Takotsubo cardiomyopathy (TTC) is a form of reversible acute cardiac dysfunction of uncertain pathogenesis, which occurs predominantly in postmenopausal women, often with antecedent severe stress. Systolic dysfunction most commonly affects the apex of the left ventricle. There is considerable uncertainty regarding the pathogenesis of TTC and the optimal diagnostic methodology. Acute catecholamine release may play a component role, but the regional hypokinesis is associated with an acute inflammatory process, with resultant early release of brain natriuretic peptide (BNP) and N-terminal pro-BNP. As the diagnosis of TTC has largely been a process of exclusion, there has been considerable underdiagnosis. The combination of demographics, preceding history, ECG appearances and N-terminal pro-BNP elevation may provide the basis for improved early diagnosis. Complete recovery takes at least several months, with a risk of recurrent episodes. Efforts to delineate pathogenesis, expedite diagnosis and evaluate residual disability may assist in the development of appropriate treatment regimens.
No related grants have been discovered for Thanh Ha Nguyen.