Publications by authors named "Anthony Chuang"

14 Publications

  • Page 1 of 1

High-sensitivity troponin in chronic kidney disease: Considerations in myocardial infarction and beyond.

Rev Cardiovasc Med 2020 Jun;21(2):191-203

School of Medicine, Flinders University of South Australia, Adelaide 5042, Australia.

Acute myocardial infarction (MI) represents one of the most common hospital encounters, with significant short-term and long-term morbidity and mortality, and frequently occurs in patients with chronic kidney disease (CKD). Cardiac troponin is an exquisitely sensitive biomarker for myocardial injury and plays an essential role in the diagnosis, risk-stratification, and management of MI. In 2017, the United States Food and Drug Administration approved Roche Diagnostics' 5 generation high-sensitivity cardiac troponin (hs-cTn) for clinical use. Whilst the improved analytical sensitivity of these new high-sensitivity troponin assays facilitate early diagnosis of MI, it also frequently identifies troponin elevations above the conventional reference threshold in the context of non-coronary conditions such as renal dysfunction, and can represent a major diagnostic challenge to clinicians. Furthermore, the optimal management strategy of patients with troponin elevation and high comorbidity burden, a common issue in patients with CKD, remains undefined. In recent years, there has been substantial research and progress undertaken in this rapidly evolving area. In this review, we aim to provide clinicians with an overview of hs-cTn in the setting of CKD as well as an update on its application and the particular considerations involved in the management of myocardial infarction, stable coronary artery disease and myocardial injury in this high risk population.
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http://dx.doi.org/10.31083/j.rcm.2020.02.17DOI Listing
June 2020

A Randomized Trial of a 1-Hour Troponin T Protocol in Suspected Acute Coronary Syndromes: The Rapid Assessment of Possible Acute Coronary Syndrome in the Emergency Department With High-Sensitivity Troponin T Study (RAPID-TnT).

Circulation 2019 11 3;140(19):1543-1556. Epub 2019 Sep 3.

South Australian Department of Health, Adelaide (D.P.C., K.L., A.B., A.S., M.J.R.E., A.C., D.W., M.H., C.P.).

Background: High-sensitivity troponin assays promise earlier discrimination of myocardial infarction. Yet, the benefits and harms of this improved discriminatory performance when incorporated within rapid testing protocols, with respect to subsequent testing and clinical events, has not been evaluated in an in-practice patient-level randomized study. This multicenter study evaluated the noninferiority of a 0/1-hour high-sensitivity cardiac troponin T (hs-cTnT) protocol in comparison with a 0/3-hour masked hs-cTnT protocol in patients with suspected acute coronary syndrome presenting to the emergency department (ED).

Methods: Patients were randomly assigned to either a 0/1-hour hs-cTnT protocol (reported to the limit of detection [<5 ng/L]) or masked hs-cTnT reported to ≤29 ng/L evaluated at 0/3-hours (standard arm). The 30-day primary end point was all-cause death and myocardial infarction. Noninferiority was defined as an absolute margin of 0.5% determined by Poisson regression.

Results: In total, 3378 participants with an emergency presentation were randomly assigned between August 2015 and April 2019. Ninety participants were deemed ineligible or withdrew consent. The remaining participants received care guided either by the 0/1-hour hs-cTnT protocol (n=1646) or the 0/3-hour standard masked hs-cTnT protocol (n=1642) and were followed for 30 days. Median age was 59 (49-70) years, and 47% were female. Participants in the 0/1-hour arm were more likely to be discharged from the ED (0/1-hour arm: 45.1% versus standard arm: 32.3%, <0.001) and median ED length of stay was shorter (0/1-hour arm: 4.6 [interquartile range, 3.4-6.4] hours versus standard arm: 5.6 (interquartile range, 4.0-7.1) hours, <0.001). Those randomly assigned to the 0/1-hour protocol were less likely to undergo functional cardiac testing (0/1-hour arm: 7.5% versus standard arm: 11.0%, <0.001). The 0/1-hour hs-cTnT protocol was not inferior to standard care (0/1-hour arm: 17/1646 [1.0%] versus 16/1642 [1.0%]; incidence rate ratio, 1.06 [ 0.53-2.11], noninferiority value=0.006, superiority value=0.867), although an increase in myocardial injury was observed. Among patients discharged from ED, the 0/1-hour protocol had a negative predictive value of 99.6% (95% CI, 99.0-99.9%) for 30-day death or myocardial infarction.

Conclusions: This in-practice evaluation of a 0/1-hour hs-cTnT protocol embedded in ED care enabled more rapid discharge of patients with suspected acute coronary syndrome. Improving short-term outcomes among patients with newly recognized troponin T elevation will require an evolution in management strategies for these patients.

Clinical Trial Registration: URL: https://www.anzctr.org.au. Unique identifier: ACTRN12615001379505.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.119.042891DOI Listing
November 2019

Multidisciplinary transcatheter aortic valve replacement heart team programme improves mortality in aortic stenosis.

Open Heart 2019;6(2):e000983. Epub 2019 Jul 29.

Cardiology, Flinders Medical Centre, Bedford Park, South Australia, Australia.

Objectives: To analyse the effect of the implementation of a transcatheter aortic valve replacement (TAVR) and multidisciplinary heart team programme on mortality in severe aortic stenosis (AS).

Methods: A retrospective, observational cohort study was performed using the echocardiography, cardiothoracic surgery and TAVR databases between 1 January 2006 and 31 December 2016. Outcomes were compared between the pre- and post-TAVR programme eras in a tertiary referral centre providing transcatheter and surgical interventions for AS.All-cause mortality within 5 years from diagnosis was determined for 3399 patients with echocardiographically defined severe AS.

Results: Of 3399 patients, there were 210 deaths (6.2%) at 30 days and 1614 deaths (47.5%) at 5 years.Overall, patients diagnosed in the post-TAVR programme era were older, with a lower ejection fraction and more severe AS, but were less comorbid.Among 705 patients undergoing intervention, those in the post-TAVR programme era were older, with a lower ejection fraction and more severe AS but no significant differences in comorbidities.Using an inverse probability weighted cohort and a Cox proportional hazards model, a significant mortality benefit was noted between eras alone (HR=0.86, 95% CI 0.77 to 0.97, p=0.015). When matching for age, comorbidities and valve severity, this benefit was more evident (HR=0.82, 95% CI 0.73 to 0.92, p=0.001).After adjusting for the presence of aortic valve intervention, a significant benefit persisted (HR=0.84, 95% CI 0.75 to 0.95, p=0.005).

Conclusion: The implementation of a TAVR programme is associated with a mortality benefit in the population with severe AS, independent of the expansion of access to intervention.
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http://dx.doi.org/10.1136/openhrt-2018-000983DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6667939PMC
February 2021

Effect of Balloon Aortic Valvuloplasty on Mortality in Patients With Severe Aortic Stenosis Prior to Conservative Treatment and Surgical or Transcatheter Aortic Valve Replacement.

Heart Lung Circ 2020 May 25;29(5):719-728. Epub 2019 Jun 25.

Flinders University, Adelaide, SA, Australia; Flinders Medical Centre, Adelaide, SA, Australia.

Background: Outcomes following an initial strategy of balloon aortic valvuloplasty (BAV) prior to medical therapy or intervention with surgical or transcatheter aortic valve replacement (SAVR or TAVR) are unclear in the modern transcatheter intervention era.

Methods: A retrospective, observational cohort study of the echocardiography, cardiothoracic surgery and TAVR databases between 1 January 2006 and 31 December 2016 was performed to compare outcomes between all patients with severe aortic stenosis (AS) treated with or without BAV prior to medical or invasive therapy.

Results: 3,142 patients were available for analysis. 223 BAV treated patients had lower mortality relative to medically treated patients, particularly early (20.1% v. 7.6% at 6 months, 58.1% v. 52.5% at 5 years). Over 5 years, the adjusted hazard ratio (HR) was 0.62 (95% CI 0.48-0.80, p < 0.001). Compared with 630 patients proceeding directly to intervention, 75 patients receiving BAV experienced a higher mortality (HR = 2.76, 95% CI 2.07-3.66, p < 0.001). No subsequent excess perioperative mortality was observed with BAV compared with those receiving surgery directly (HR = 1.45, 95% CI 0.91-2.31, p = 0.117).

Conclusions: The risk associated with BAV is low, and improves mortality compared with medical therapy. Balloon aortic valvuloplasty treated patients have poorer outcomes, but treatment with BAV does not increase perioperative mortality and may lessen it.
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http://dx.doi.org/10.1016/j.hlc.2019.06.717DOI Listing
May 2020

The appropriateness of coronary investigation in myocardial injury and type 2 myocardial infarction (ACT-2): A randomized trial design.

Am Heart J 2019 02 25;208:11-20. Epub 2018 Oct 25.

Department of Cardiology, Flinders Medical Centre, Adelaide, Australia; College of Medicine and Public Health, Flinders University of South Australia, Adelaide, Australia. Electronic address:

Background: Elevated troponin level findings among patients presenting with suspected acute coronary syndrome (ACS) or another intercurrent illness undeniably identifies patients at increased risk of mortality. Whilst enhancing our capacity to discriminate risk, the use of high-sensitivity troponin assays frequently identifies patients with myocardial injury (i.e. troponin rise without acute signs of myocardial ischemia) or type 2 myocardial infarction (T2MI; oxygen supply-demand imbalance). This leads to the clinically challenging task of distinguishing type 1 myocardial infarction (T1MI; coronary plaque rupture) from myocardial injury and T2MI in the context of concurrent acute illness. Diagnostic discernment in this context is crucial because MI classification has implications for further investigation and care. Early invasive management is of well-established benefit among patients with T1MI. However, the appropriateness of this investigation in the heterogeneous context of T2MI, where there is high competing mortality risk, remains unknown. Although coronary angiography in T2MI is advocated by some, there is insufficient evidence in existing literature to support this opinion as highlighted by current national guidelines.

Objective: The objective is to evaluate the clinical and economic impact of early invasive management with coronary angiography in T2MI in terms of all-cause mortality and cost effectiveness.

Design: This prospective, pragmatic, multicenter, randomized trial among patients with suspected supply demand ischemia leading to troponin elevation (n=1,800; T2MI [1,500], chronic myocardial injury [300]) compares the impact of invasive angiography (or computed tomography angiography as per local preference) within 5 days of randomization versus conservative management (with or without functional testing at clinician discretion) on all-cause mortality by 2 years. Randomized treatment allocation will be stratified by baseline estimated risk of mortality using the Acute Physiology, Age, and Chronic Health Evaluation (APACHE) III risk score. Cost-effectiveness will be evaluated by follow-up on clinical events, quality of life, and resource utilization over 24 months.

Summary: Ascertaining the most appropriate first-line investigative strategy for these commonly encountered high-risk T2MI patients in a randomized comparative study will be pivotal in informing evidence-based guidelines that lead to better patient and health care outcomes.
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http://dx.doi.org/10.1016/j.ahj.2018.09.016DOI Listing
February 2019

A Prospective Randomised Controlled Trial of a Single Intravenous Infusion of Ferric Carboxymaltose vs Single Intravenous Iron Polymaltose or Daily Oral Ferrous Sulphate in the Treatment of Iron Deficiency Anaemia in Pregnancy.

Semin Hematol 2018 10 25;55(4):223-234. Epub 2018 Apr 25.

Duke-NUS Medical School Singapore, Centre for Quantitative Medicine, Office of Clinical Sciences, The Academia, Singapore, Singapore.

Iron deficiency anaemia (IDA) is the most common nutritional deficiency affecting pregnant women worldwide. This study aims to compare the efficacy and safety of a newly available intravenous (IV) iron preparation, ferric carboxymaltose (FCM), against IV iron polymaltose (IPM), and standard oral iron (ferrous sulphate) for the treatment of IDA in pregnancy. This is an open-labelled prospective randomised controlled trial (RCT) with intention-to-treat analysis conducted at a primary health care facility with a single tertiary referral centre in Launceston. Tasmania, Australia. A 3-arm randomised controlled trial was conducted comparing a single IV infusion of 1000mg of FCM (n = 83 patients) over 15 minutes against a single IV infusion of 1000mg of IPM (n = 82) over 2 hours against 325mg daily oral ferrous sulphate (n = 81) until delivery, for the treatment of IDA in pregnancy. A total of 246 consecutive pregnant women were recruited between September 2013 and July 2014. The median age was 28 years, with a median and mean gestation of 27 weeks. The median serum ferritin was 9µg/L, with a mean of 13µg/L. The mean haemoglobin (Hb) was 114g/L. The primary outcome was the change in ferritin and Hb levels at 4 weeks after intervention. Secondary outcomes included ferritin and Hb improvements at predelivery, safety, tolerability, quality of life (QoL), cost utility, and fetal outcomes. The mean Hb level differences between the baseline intervention time point and 4 weeks thereafter were significantly higher in the FCM versus the oral group by 4.35g/L (95% CI: 1.64-7.05; P = 0.0006) and in the IPM vs the oral group by 4.08g/L (95% CI: 1.57-6.60; P = 0.0005), but not different between the FCM and IPM groups (0.26g/L; 95% CI: -2.59 to 3.11; P = 0.9740). The mean ferritin level differences were significantly higher at 4 weeks in the FCM vs oral iron group by 166µg/L (95% CI: 138-194; P < 0.0001) and in the IPM vs oral iron group by 145µg/L (95% CI: 109-1180, P < 0.0001), but not between the 2 IV groups (21.5µg/L; 95% CI: -23.9 to 66.9; P = 0.4989). Administration of IV FCM during pregnancy was safe and better tolerated than IV IPM or oral iron. Compliance to oral iron was the lowest amongst treatment groups with one-third of the patients missing doses of daily iron tablets. Significant improvement in overall QoL scores was observed in both IV iron supplement groups by achieving normal ferritin following effective and prompt repletion of iron stores, compared to the oral iron group (P = 0.04, 95% CI: 21.3, 1.8). The overall cost utility of IV FCM and IV IPM appear to be similar to oral iron. There were no differences in the fetal outcomes between the 3 trial arms. In conclusion, this study demonstrates that a single IV iron infusion is an effective and safe option for treatment of IDA during pregnancy. FCM was more convenient than other treatments. Rapid parenteral iron repletion can improve iron stores, Hb levels and QoL in pregnant women, with ongoing benefits until delivery. Integration of IV iron for IDA in pregnancy can potentially improve pregnancy outcomes for the mother. Update of guidelines to integrate the use of new IV iron preparations in pregnancy is warranted.
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http://dx.doi.org/10.1053/j.seminhematol.2018.04.006DOI Listing
October 2018

Invasive management of acute coronary syndrome: Interaction with competing risks.

Int J Cardiol 2018 Oct 19;269:13-18. Epub 2018 Jul 19.

School of Medicine, Flinders University of South Australia, Adelaide, Australia; Department of Cardiovascular Medicine, Southern Adelaide Local Health Network, Adelaide, Australia.

Background: The aim of this study was to characterise the interaction between ACS- and non-ACS-risk on the benefits of invasive management in patients presenting with acute coronary syndrome (ACS).

Methods: Consecutive patients admitted to a tertiary hospital's Cardiac Care Unit in the months of July-December, 2003-2011 with troponin elevation (>30 ng/L) were included. "ACS-specific-risk" was estimated using the GRACE score and "non-ACS-risk" was estimated using the Charlson-Comorbidity-Index (CCI). Inverse-probability-of-treatment weighting was used to adjust for baseline differences between patients who did or did not receive invasive management. A multivariable flexible parametric model was used to characterise the time-varying hazard.

Results: In total, 3057 patients were included with a median follow-up of 9.0 years. Based on CCI, 1783 patients were classified as 'low-non-ACS risk' (CCI ≤ 1; invasive management 81%; 12-month mortality 5%), 820 as 'medium-non-ACS risk' (CCI 2-3; invasive management 68%; 12-month mortality 13%), and 468 as 'high-non-ACS risk' (CCI ≥ 4; invasive management 47%; 12-month mortality 29%). After adjustment, invasive management was associated with a significant reduction in one-year overall-mortality in the 'low-risk' and 'medium-risk' groups (HR = 0.38, 95%CI:0.26-0.56; HR = 0.46, 95%CI:0.32-0.67); but not in the 'high-risk' group (HR = 1.02, 95%CI:0.67-1.56). The absolute benefit of invasive management was greatest with higher baseline ACS-risk, with a non-linear interaction between ACS- and non-ACS-risk.

Conclusions: There is a complex interaction between ACS- and non-ACS-risk on the benefit of invasive management. These results highlight the need to develop robust methods to objectively quantify risk attributable to non-ACS comorbidities in order to make informed decisions regarding the use of invasive management in individuals with numerous comorbidities.
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http://dx.doi.org/10.1016/j.ijcard.2018.07.078DOI Listing
October 2018

A randomized trial of a 1-hour troponin T protocol in suspected acute coronary syndromes: Design of the Rapid Assessment of Possible ACS In the emergency Department with high sensitivity Troponin T (RAPID-TnT) study.

Am Heart J 2017 Aug 18;190:25-33. Epub 2017 May 18.

School of Medicine, Flinders University of South Australia, Adelaide, Australia; South Australian Department of Health, Adelaide, Australia. Electronic address:

Background: Protocols incorporating high-sensitivity troponin to guide decision making in the disposition of patients with suspected acute coronary syndromes (ACS) in the emergency department have received a lot of attention. Traditionally, patients with chest pain have required long periods of observation in emergency department before being deemed safe for discharge. In an era of limited health service resources, a protocol that could discharge patients safely within an hour of presentation is extremely attractive. Unfortunately, despite incorporation into some guidelines, these protocols have not been subjected to randomized comparisons evaluating safety, effectiveness, and cost-effectiveness.

Objective: This study is designed to provide the evidence required to allow key decision makers to implement these protocols: specifically, to provide evidence that a decision rule based on 0- and 1-hour high-sensitivity troponin T (hs-TnT) is safe, provides noninferior outcomes in all patients with suspected ACS, and that implementation of a rapid troponin protocol leads to efficient care.

Design: This prospective pragmatic trial (n=5,400, 5 hospitals) randomly allocates patients with suspected ACS to either a 0/1-hour hs-TnT protocol as advocated in clinical guidelines, versus usual care of standard troponin reporting evaluated at 3 and 6hours. The primary effectiveness composite end points of this study are all-cause death and new/recurrent ACS within 30days. To evaluate cost-effectiveness, follow-up will determine clinical events, quality of life, and resource utilization within 12 months.

Summary: Demonstrating that a 0/1-hour hs-TnT protocol improves the effectiveness and efficiency of care within a robust comparative study will fill an evidence gap that currently limits the translation of more precise hs-TnT testing into better patient and health service outcomes.
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http://dx.doi.org/10.1016/j.ahj.2017.05.004DOI Listing
August 2017

P2Y12 Inhibitor Pre-Treatment in Non-ST-Elevation Acute Coronary Syndrome: A Decision-Analytic Model.

J Clin Med 2016 Aug 17;5(8). Epub 2016 Aug 17.

Cardiology Department, Flinders University/Southern Adelaide Local Health Network, Adelaide 5042, Australia.

Current guidelines recommend initiation of a P2Y12 inhibitor for all patients with non-ST-elevation acute coronary syndrome (NSTE-ACS) at the time of diagnosis (pre-treatment); however, there are no randomized trials directly comparing pre-treatment with initiation at the time of angiography to support this practice. We explore clinical and institutional parameters potentially associated with benefit with this strategy in a decision-analytic model based on available evidence from randomised trials. A decision analysis model was constructed comparing three P2Y12 inhibitors in addition to aspirin in patients with NSTE-ACS. Based on clinical trial data, the cumulative probability of 30 day mortality, myocardial infarction (MI) and major bleeding were determined, and used to calculate the net clinical benefit (NCB) with and without pre-treatment. Sensitivity analysis was performed to assess the relationship between NCB and baseline ischemic risk, bleeding risk, time to angiography and local surgical revascularization rates. Pre-treatment with ticagrelor and clopidogrel was associated with a greater than 50% likelihood of providing a >1% increase in 30 day NCB when baseline estimated ischemic risk exceeds 11% and 14%, respectively. Prasugrel pre-treatment did not achieve a greater than 50% probability of an increase in NCB regardless of baseline ischemic risk. Institutional surgical revascularization rates and time to coronary angiography did not correlate with the likelihood of benefit from P2Y12 pre-treatment. In conclusion, pre-treatment with P2Y12 inhibition is unlikely to be beneficial to the majority of patients presenting with NSTE-ACS. A tailored assessment of each patient's individual ischemic and bleeding risk may identify those likely to benefit.
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http://dx.doi.org/10.3390/jcm5080072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4999792PMC
August 2016

Viral/Nonviral Chimeric Nanoparticles To Synergistically Suppress Leukemia Proliferation via Simultaneous Gene Transduction and Silencing.

ACS Nano 2016 09 5;10(9):8705-14. Epub 2016 Aug 5.

Department of Pharmaceutical Sciences, ‡Department of Chemical Engineering and Materials Science, §Department of Biological Sciences, ∥Division of Hematology/Oncology, ⊥Department of Molecular Biology and Biochemistry, and #Department of Biomedical Engineering, University of California , Irvine, California 92697, United States.

Single modal cancer therapy that targets one pathological pathway often turns out to be inefficient. For example, relapse of chronic myelogenous leukemia (CML) after inhibiting BCR-ABL fusion protein using tyrosine kinase inhibitors (TKI) (e.g., Imatinib) is of significant clinical concern. This study developed a dual modal gene therapy that simultaneously tackles two key BCR-ABL-linked pathways using viral/nonviral chimeric nanoparticles (ChNPs). Consisting of an adeno-associated virus (AAV) core and an acid-degradable polymeric shell, the ChNPs were designed to simultaneously induce pro-apoptotic BIM expression by the AAV core and silence pro-survival MCL-1 by the small interfering RNA (siRNA) encapsulated in the shell. The resulting BIM/MCL-1 ChNPs were able to efficiently suppress the proliferation of BCR-ABL+ K562 and FL5.12/p190 cells in vitro and in vivo via simultaneously expressing BIM and silencing MCL-1. Interestingly, the synergistic antileukemic effects generated by BIM/MCL-1 ChNPs were specific to BCR-ABL+ cells and independent of a proliferative cytokine, IL-3. The AAV core of ChNPs was efficiently shielded from inactivation by anti-AAV serum and avoided the generation of anti-AAV serum, without acute toxicity. This study demonstrates the development of a synergistically efficient, specific, and safe therapy for leukemia using gene carriers that simultaneously manipulate multiple and interlinked pathological pathways.
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http://dx.doi.org/10.1021/acsnano.6b04155DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5602606PMC
September 2016

The predictive value of high sensitivity-troponin velocity within the first 6h of presentation for cardiac outcomes regardless of acute coronary syndrome diagnosis.

Int J Cardiol 2016 Feb 23;204:106-11. Epub 2015 Nov 23.

School of Medicine, Flinders University of South Australia, Adelaide, Australia; Department of Cardiovascular Medicine, Southern Adelaide Local Health Network, Adelaide, Australia. Electronic address:

Background: Low-range troponin elevations without clear coronary manifestations remain a major diagnostic challenge. We sought to determine if troponin velocity could allow for early identification of patients without an obvious cardiac diagnosis and who are at increased risk for cardiac-specific events.

Methods & Results: All patients presenting to South Australian public hospitals between 1 September 2011 and 30 September 2012, with at least two troponin measurements during the first 6h after ED presentation were included. Diagnoses were classified as 'coronary', 'non-coronary cardiac', and 'non-cardiac' using the International Classification of Diseases 10 codes. The relationship between troponin velocity and cardiac-specific mortality and combined cardiac outcome (death and myocardial infarction) was assessed using Fine and Gray competing risk models in patients with an initial troponin <52 ng/L. Sensitivity analyses were performed using different initial and maximum troponin cut-off values. In total, 7300 patients were identified. A troponin velocity of 2.5 ng/L/h or greater in the non-cardiac (n=2793) patient group was significantly associated with an increased risk for 12-month cardiac mortality (sub-hazard ratio [SHR] 2.90, 95% CI 1.33-6.34) and combined cardiac outcome (SHR 2.08, 95% CI 1.01-4.27). This association was consistent for coronary (n=3835) and non-coronary cardiac (n=672) patient groups, and remained after sensitivity analyses.

Conclusions: The significant association observed across all patient groups suggests that troponin velocity could be used for early risk stratification of patients with low-range troponin elevations without clear cardiac symptoms. These results may help guide future clinical trials aimed at assessing the utility of cardiac-targeted interventions in this challenging patient population.
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http://dx.doi.org/10.1016/j.ijcard.2015.11.132DOI Listing
February 2016

One problem two issues! Left ventricular systolic and diastolic dysfunction in aortic stenosis.

Ann Transl Med 2014 Jan;2(1):10

1 Division of Cardiothoracic Surgery, Department of Surgery, Texas A & M Health Science Center at Scott & White Memorial Hospital, Temple, TX, USA ; 2 Division of Cardiothoracic Surgery, Prince of Wales & Sydney Children's Hospital, Barker Street, Randwick, Sydney, NSW, Australia ; 3 Liverpool Heart and Chest Hospital, NHS Foundation Trust, Liverpool, UK.

Reports suggested that immediate post-aortic valve replacement (AVR); left ventricular (LV) dysfunction may be an important risk for morbidity and mortality in patients requiring positive inotropic support. Several factors have been identified as significant prognostic factors i.e., LV systolic dysfunction, LV diastolic dysfunction (LV-DD), heart failure and myocardial infarction (MI). Specific to pathophysiological changes associated with AS, markers of systolic LV function (e.g., LVEF) have been extensively studied in management, yet only a few studies have analysed the association between LV-DD and immediate post-operative LV dysfunction This review brings together the current body of evidence on this issue.
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http://dx.doi.org/10.3978/j.issn.2305-5839.2013.06.05DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4200657PMC
January 2014

Redistribution of terbium ions across acetylcholine receptor-enriched membranes induced by agonist desensitization.

Biophys J 2009 Apr;96(7):2637-47

Department of Information Technology, Gilead Sciences, Foster City, California, USA.

Using small-angle x-ray diffraction from centrifugally oriented acetylcholine receptor (AChR) enriched membranes coupled with anomalous scattering from terbium ions (Tb3+) titrated into presumed Ca2+ binding sites, we have mapped the distribution of Tb3+ perpendicular to the membrane plane using a heavy atom refinement algorithm. We have compared the distribution of Tb3+ in the closed resting state with that in the carbamylcholine-desensitized state. In the closed resting state we find 45 Tb3+ ions distributed in 10 narrow peaks perpendicular to the membrane plane. Applying the same refinement procedure to the data from carbamylcholine desensitized AChR we find 18 fewer Tb3+ ions in eight peaks, and slight rearrangements of Tb3+ density in the peaks near the ends of the AChR ion channel pore. These agonist dependent changes in the Tb3+ stoichiometry and distribution suggest a likely role for multivalent cations in stabilizing the different functional states of the AChR, and the changes in the Tb3+ distribution at the two ends of the pore suggest a potential role for multivalent cations in the gating of the ion channel.
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http://dx.doi.org/10.1016/j.bpj.2008.08.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2711283PMC
April 2009

Agonist-induced transitions of the acetylcholine receptor.

Ann N Y Acad Sci 2003 Sep;998:101-13

Department of Neurology, University of California, Davis, Davis, California 95616, USA.

Anti-acetylcholine receptor (AChR) monoclonal antibody 383C binds to the beta-hairpin loop alpha(187-199) of only one of the two Torpedo AChR alpha subunits. The loop recognized is associated with the alpha subunit corresponding to the high-affinity d-tubocurarine (dTC) binding site. Desensitization of the receptor with carbamylcholine completely blocks the binding of 383C. Mild reduction of AChR alpha subunit cys 192-193 disulfide with DTT and subsequent reaction with 5-iodoacetamidofluorescein label only the high-affinity dTC alpha subunit. Rhodamine-labeled alpha-bungarotoxin (R-Btx) binds to the unlabeled AChR alpha subunit as monitored by fluorescence resonance energy transfer between the fluorescein and rhodamine dyes. A 10-A contraction of the distance between the dyes is observed following the addition of carbamylcholine. In a small angle X-ray diffraction experiment exploiting anomalous X-ray scattering from Tb(III) ions titrated into AChR Ca(II) binding sites, we find evidence for a change in the Tb(III) ion distribution in the region of the ion channel following addition of carbamylcholine to the AChR. The carbamylcholine-induced loss of the 383C epitope, the 10-A contraction of the beta-hairpin loop, and the loss of multivalent cations from the channel likely represent the first molecular transitions leading to AChR channel opening.
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http://dx.doi.org/10.1196/annals.1254.012DOI Listing
September 2003