Prognostic performance of soluble urokinase plasminogen activator receptor for heart failure or mortality in Western and Asian patients with acute breathlessness

AIMS

The performance of circulating soluble urokinase plasminogen activator receptor (suPAR) for predicting the composite endpoint of subsequent heart failure (HF) hospitalisation and/or death at 1 year was assessed in (i) patients with undifferentiated breathlessness, and generalisability was compared in (ii) disparate Western versus Asian sub-cohorts, and in (iii) the sub-cohort adjudicated with HF.

METHODS AND RESULTS

Patients with acute breathlessness were recruited from the emergency departments in New Zealand (NZ, n = 612) and Singapore (n = 483). suPAR measured in the presentation samples was higher in patients incurring the endpoint (n = 281) compared with survivors (5.2 ng/mL vs 3.1 ng/mL, P < 0.0001). The discriminative power of suPAR for endpoint prediction was c-statistic of 0.77 in the combined population, but was superior in Singapore than NZ (c-statistic: 0.83 vs 0.71, P < 0.0001). Although the highest suPAR tertile (>4.37 ng/mL) was associated with risks of >4-fold in NZ, >20-fold in Singapore, and > 3-fold in HF for incurring the outcome, there was no interaction between country and suPAR levels after adjustment. Multivariable analysis indicated suPAR to be robust in predicting HF/death at 1-year [hazard ratio: 1.9 (95% CI:1.7 to 2.03) per SD increase] and improved risk discrimination for outcome prediction in HF (∆0.06) and for those with NT-proBNP >1000 pg/mL (∆0.02).

CONCLUSION

suPAR is a strong independent predictor of HF and/or death at 1 year in acutely breathless patients, in both Asian and Western cohorts, and in HF. suPAR may improve stratification of acutely breathless patients, and in acute HF, for risk of later onset of heart failure or mortality.

Cardiac effects of myoregulin in ischemia-reperfusion

Myoregulin is a recently discovered micropeptide that controls calcium levels by inhibiting the intracellular calcium pump sarco-endoplasmic reticulum Ca2+-ATPase (SERCA). Keeping calcium levels balanced in the heart is essential for normal heart functioning, thus myoregulin has the potential to be a crucial regulator of cardiac muscle performance by reducing the rate of intracellular Ca2+ uptake. We provide the first report of myoregulin mRNA expression in human heart tissue, absence of expression in human plasma, and the effects of myoregulin on cardiac hemodynamics in an ex vivo Langendorff isolated rat heart model of ischemia/reperfusion. In this preliminary study, myoregulin provided a cardio-protective effect, as assessed by preservation of left ventricular contractility and relaxation, during ischemia/reperfusion. This study provides the foundation for future research in this area.

Derivation and Validation of Thresholds Using Synthetic Data Methods for Single-Test Screening of Emergency Department Patients with Possible Acute Myocardial Infarction Using a Point-of-Care Troponin Assay

BACKGROUND

Single-sample (screening) rule-out of acute myocardial infarction (AMI) with troponin requires derivation of a single-test screening threshold. In data sets with small event numbers, the lowest one or two concentrations of myocardial infarction (MI) patients dictate the threshold. This is not optimal. We aimed to demonstrate a process incorporating both real and synthetic data for deriving such thresholds using a novel pre-production high-precision point-of-care assay.

METHODS

cTnI concentrations were measured from thawed plasma using the Troponin I Next (TnI-Nx) assay (i-STAT; Abbott) in adults on arrival to the emergency department with symptoms suggestive of AMI. The primary outcome was an AMI or cardiac death within 30 days. We used internal-external validation with synthetic data production based on clinical and demographic data, plus the measured TnI-Nx concentration, to derive and validate decision thresholds for TnI-Nx. The target low-risk threshold was a sensitivity of 99% and a high-risk threshold specificity of >95%.

RESULTS

In total, 1356 patients were included, of whom 191 (14.1%) had the primary outcome. A total of 500 synthetic data sets were constructed. The mean low-risk threshold was determined to be 5 ng/L. This categorized 38% (95% CI, 6%-68%) to low-risk with a sensitivity of 99.0% (95% CI, 98.6%-99.5%) and a negative predictive value of 99.4% (95% CI, 97.6%-99.8%). A similarly derived high-risk threshold of 25 ng/L had a specificity of 95.0% (95% CI, 94.8%-95.1%) and a positive predictive value of 74.8% (95% CI, 71.5%-78.0%).

CONCLUSIONS

With the TnI-Nx assay, we successfully demonstrated an approach using synthetic data generation to derive low-risk thresholds for safe and effective screening.

Circulating erythroferrone has diagnostic utility for acute decompensated heart failure in patients presenting with acute or worsening dyspnea

Objectives

In dyspneic patients with atrial fibrillation (AF) or obesity, the diagnostic performance of NT-proBNP for acute heart failure is reduced. We evaluated the erythroblast derived protein erythroferrone (ERFE) as an ancillary biomarker for the diagnosis of acute decompensated heart failure (ADHF) in these comorbid subgroups in both Western and Asian populations.

Methods

The diagnostic performance of ERFE (Intrinsic Lifesciences) and NT-proBNP (Roche Cobas e411) for ADHF was assessed in 479 New Zealand (NZ) and 475 Singapore (SG) patients presenting with breathlessness.

Results

Plasma ERFE was higher in ADHF, compared with breathlessness from other causes, in both countries (NZ; 4.9 vs. 1.4 ng/ml, p < 0.001) and (SG; 4.2 vs. 0.4 ng/ml, p = 0.021). The receiver operating characteristic (ROC) areas under the curve (AUCs) for discrimination of ADHF were reduced in the NZ cohort compared to SG for ERFE (0.75 and 0.84, p = 0.007) and NT-proBNP (0.86 and 0.92, p = 0.004). Optimal cut-off points for ERFE yielded comparable sensitivity and positive predictive values in both cohorts, but slightly better specificity, negative predictive values and accuracy in SG compared with NZ. In patients with AF, the AUC decreased for ERFE in each cohort (NZ: 0.71, n = 105, SG: 0.61, n = 44) but increased in patients with obesity (NZ: 0.79, n = 150, SG: 0.87, n = 164).

Conclusions

Circulating ERFE is higher in patients with ADHF than in other causes of new onset breathlessness with fair diagnostic utility, performing better in Asian than in Western patients. The diagnostic performance of ERFE is impaired in patients with AF but not patients with obesity.

Personalized diagnosis in suspected myocardial infarction

BACKGROUND

In suspected myocardial infarction (MI), guidelines recommend using high-sensitivity cardiac troponin (hs-cTn)-based approaches. These require fixed assay-specific thresholds and timepoints, without directly integrating clinical information. Using machine-learning techniques including hs-cTn and clinical routine variables, we aimed to build a digital tool to directly estimate the individual probability of MI, allowing for numerous hs-cTn assays.

METHODS

In 2,575 patients presenting to the emergency department with suspected MI, two ensembles of machine-learning models using single or serial concentrations of six different hs-cTn assays were derived to estimate the individual MI probability (ARTEMIS model). Discriminative performance of the models was assessed using area under the receiver operating characteristic curve (AUC) and logLoss. Model performance was validated in an external cohort with 1688 patients and tested for global generalizability in 13 international cohorts with 23,411 patients.

RESULTS

Eleven routinely available variables including age, sex, cardiovascular risk factors, electrocardiography, and hs-cTn were included in the ARTEMIS models. In the validation and generalization cohorts, excellent discriminative performance was confirmed, superior to hs-cTn only. For the serial hs-cTn measurement model, AUC ranged from 0.92 to 0.98. Good calibration was observed. Using a single hs-cTn measurement, the ARTEMIS model allowed direct rule-out of MI with very high and similar safety but up to tripled efficiency compared to the guideline-recommended strategy.

CONCLUSION

We developed and validated diagnostic models to accurately estimate the individual probability of MI, which allow for variable hs-cTn use and flexible timing of resampling. Their digital application may provide rapid, safe and efficient personalized patient care.

TRIAL REGISTRATION NUMBERS

Data of following cohorts were used for this project: BACC ( www.

CLINICALTRIALS

gov ; NCT02355457), stenoCardia ( www.

CLINICALTRIALS

gov ; NCT03227159), ADAPT-BSN ( www.australianclinicaltrials.gov.au ; ACTRN12611001069943), IMPACT ( www.australianclinicaltrials.gov.au , ACTRN12611000206921), ADAPT-RCT ( www.anzctr.org.au ; ANZCTR12610000766011), EDACS-RCT ( www.anzctr.org.au ; ANZCTR12613000745741); DROP-ACS ( https://www.umin.ac.jp , UMIN000030668); High-STEACS ( www.

CLINICALTRIALS

gov ; NCT01852123), LUND ( www.

CLINICALTRIALS

gov ; NCT05484544), RAPID-CPU ( www.

CLINICALTRIALS

gov ; NCT03111862), ROMI ( www.

CLINICALTRIALS

gov ; NCT01994577), SAMIE ( https://anzctr.org.au ; ACTRN12621000053820), SEIGE and SAFETY ( www.

CLINICALTRIALS

gov ; NCT04772157), STOP-CP ( www.

CLINICALTRIALS

gov ; NCT02984436), UTROPIA ( www.

CLINICALTRIALS

gov ; NCT02060760).

Diagnostic and prognostic performance of the ratio between high-sensitivity cardiac troponin I and troponin T in patients with chest pain

Background

Elevations of high-sensitivity cardiac troponin (hs-cTn) concentrations not related to type 1 myocardial infarction are common in chest pain patients presenting to emergency departments. The discrimination of these patients from those with type 1 myocardial infarction (MI) is challenging and resource-consuming. We aimed to investigate whether the hs-cTn I/T ratio might provide diagnostic and prognostic increment in this context.

Methods

We calculated the hs-cTn I/T ratio in 888 chest pain patients having hs-cTnI (Abbott Laboratories) or hs-cTnT (Roche Diagnostics) concentrations above the respective 99^th percentile at 2 hours from presentation. All patients were followed for one year regarding mortality.

Results

The median hs-cTn I/T ratio was 3.45 (25^th, 75^th percentiles 1.80–6.59) in type 1 MI patients (n = 408 ☯46.0%]), 1.18 (0.81–1.90) in type 2 MI patients (n = 56 ☯6.3%]) and 0.67 (0.39–1.12) in patients without MI. The hs-cTn I/T ratio provided good discrimination of type 1 MI from no type 1 MI (area under the receiver-operator characteristic curve 0.89 ☯95% confidence interval 0.86–0.91]), of type 1 MI from type 2 MI (area under the curve 0.81 ☯95% confidence interval 0.74–0.87]), and was associated with type 1 MI in adjusted analyses. The hs-cTn I/T ratio provided no consistent prognostic value.

Conclusions

The hs-cTn I/T ratio appears to be useful for early diagnosis of type 1 MI and its discrimination from type 2 MI in chest pain patients presenting with elevated hs-cTn. Differences in hs-cTn I/T ratio values may reflect variations in hs-cTn release mechanisms in response to different types of myocardial injury.

Comparative performances of soluble urokinase plasminogen activator receptor and Mid-regional proADM to predict composite death and new heart failure rehospitalisation in acutely breathless patients

Background

Soluble urokinase plasminogen activator receptor (suPAR) is a pleotropic receptor, capable of orchestrating plaque vulnerability and vascular immune dysfunction. Mid-regional pro-adrenomedullin (MR-proADM) is the stable peptide precursor of adrenomedullin, with concentrations reflective of vasodilation and cardiac remodelling. We compared the prognostic performances of suPAR and MR-proADM for the composite clinical endpoint of death and new heart failure (HF) in patients with undifferentiated breathlessness.

Methods

Patients presenting to hospital with the primary complaint of acute dyspnoea were recruited in New Zealand (n=612) and in Singapore (n=483)]. Baseline plasma measurements were undertaken for suPAR (ViroGates) and MR-proADM (Thermo Scientific). Cardiac biomarker levels of NT-proBNP (Roche) was available on all patients. Statistical assessment was made using SPSS v28 (IBM), with all biomarkers treated as continuous variables and presented as median [interquartile range (IQR)]. Prognostic performance of suPAR, MR-proADM and NT-proBNP to predict the composite clinical endpoint of death/new HF at 90-days and 1-yr were assessed using receiver operator curve (ROC) area under the curve (AUC) analysis (Z-scores) and Cox hazard regression analysis (per doubling of biomarker concentrations) after adjustment for traditional risk factors. P-value &lt;0.05 was considered statistically significant.

Results

In the entire acutely breathless cohort [median age: 65 years (IQR: 52.9–76.0), 63.1% males], 343/1095 of patients had the final adjudication of ADHF. suPAR and MR-proADM concentrations were higher with increasing age (Spearmans rho, r&gt;0.46, P&lt;0.0001), lower eGFR (r&gt;0.58, P&lt;0.0001) and in those with ADHF (r&gt;0.40, P&lt;0.0001). During the follow-up period, 122 patients were categorised with death/new HF by 90-days, rising to 281 at 1-year. suPAR and MR-proADM were able to predict death/new HF at 90-days (both ROC-AUC &gt;0.77) and at 1-year (both ROC-AUC ≥0.78) (Table 1). All markers were however less accurate in predicting this endpoint in the presence of ADHF (ROC-AUC &lt;0.71). After adjustment in Cox-regression modelling, suPAR obtained HR &gt;1.35 per doubling of suPAR concentrations (P=0.001) for outcomes at 90-days and at 1-year (Table 2), achieving the highest prognostic performance for this clinical endpoint, followed by NT-proBNP (HR &gt;1.29) (Table 2), whilst MR-proADM was not an independent predictor of death/HF in this cohort. suPAR was also an independent predictor of death/HF for patients with ADHF, obtaining HR &gt;1.35 per doubling of concentrations. Above a cut-off concentration of 3.6 ng/mL, suPAR was associated with a HR of 2.1 (95% CI: 1.55–2.91) for death/HF at 1-year for acutely dyspnoeic patients.

Conclusion

suPAR concentrations is superior than MR-proADM in predicting the clinical end-point of death/HF at 1-year in this cohort. It may aid in risk-stratification strategies for the management of acutely breathless patients.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): National Heart Foundation of New ZealandHealth Research Council of New Zealand

Assays Specific for BNP1-32 and NT-proBNP Exhibit a Similar Performance to Two Widely Used Assays in the Diagnosis of Heart Failure

BACKGROUND

Secretion of cardioprotective B-type natriuretic peptide 1-32 (BNP1-32) is increased proportionately with cardiac dysfunction, but its measurement in plasma is difficult. Therefore, less specific BNP and amino-terminal proBNP (NT-proBNP) assays that detect the precursor molecule proBNP alongside BNP or NT-proBNP metabolites were developed to reflect BNP1-32 secretion and are now mandated in the diagnosis of heart failure (HF). We compared the diagnostic performance of 2 widely used clinical assays: the Roche proBNPII assay, and Abbott BNP assay, against our recently developed in-house assays that measure either intact BNP1-32 or NT-proBNP.

METHODS

EDTA plasma samples obtained from patients presenting with breathlessness (n = 195, 60 [31%] with clinically adjudicated HF) were assayed using the Roche NT-proBNP and our specific in-house BNP1-32 and NTBNP assays. A subset (n = 75) were also assessed with the Abbott BNP assay.

RESULTS

Roche NT-proBNP was highly correlated with BNP1-32 and NTBNP (Spearman rho = 0.92 and 0.90, respectively, both Ps < 0.001), and all 3 assays similarly discriminated acute HF from other causes of breathlessness (ROC analysis areas under the curve 0.85-0.89). The Abbott BNP assay performed similarly to the other assays. Roche NT-proBNP and BNP1-32 assays had similar sensitivity (83% and 80%), specificity (83% and 84%), positive (70% and 71%) and negative (91% and 90%) predictive values, and accuracy (both 83%) at their optimal cutoffs of 1536 and 12 ng/L, respectively.

CONCLUSIONS

Since all assays exhibited similar performance in the diagnosis of HF, currently mandated assays provide a reliable proxy for circulating concentrations of active BNP1-32 in HF diagnosis.

Plasma Clearance of B-Type Natriuretic Peptide (BNP) before and after Bariatric Surgery for Morbid Obesity

BACKGROUND

Obese patients have lower plasma concentrations of the cardiac natriuretic peptides (NPs) than their age- and sex-matched counterparts. This may reflect lower production and/or increased peptide clearance. It is unclear whether NP bioactivity is affected by obesity.

METHODS

We studied the effects of obesity on B-type natriuretic peptide (BNP) clearance and bioactivity by comparing results from standardized intravenous infusions of BNP administered 2 weeks before and 6 months after bariatric surgery in 12 consecutive patients with morbid obesity (body mass index, BMI > 35 kg/m2). Anthropometric, clinical, neurohormonal, renal, and echocardiographic variables were obtained pre- and postsurgery. Pre- vs postsurgery calculated intrainfusion peptide clearances were compared.

RESULTS

BMI (44.3 ± 5.0 vs 33.9 ± 5.2 kg/m2, P < 0.001) and waist circumference (130.3 ± 11.9 vs 107.5 ± 14.7 cm, P < 0.001) decreased substantially after bariatric surgery. Calculated plasma clearance of BNP was reduced (approximately 30%) after surgery. Though not controlled for, sodium intake was presumably lower after bariatric surgery. Despite this, preinfusion endogenous plasma NP concentrations did not significantly differ between pre- and postsurgery studies. The ratio of plasma N-terminal (NT)-proBNP to 24 h urine sodium excretion was higher postsurgery (P = 0.046; with similar nonsignificant findings for BNP, atrial NP (ANP) and NT-proANP), indicating increased circulating NPs for a given sodium status. Mean plasma NP concentrations for given calculated end-systolic wall stress and cardiac filling pressures (as assessed by echocardiographic E/e') rose slightly, but not significantly postsurgery. Second messenger, hemodynamic, renal, and neurohormonal responses to BNP were not altered between studies.

CONCLUSION

Obesity is associated with increased clearance, but preserved bioactivity, of BNP.

Analytical and biological assessment of circulating human erythroferrone

BACKGROUND

Erythroferrone (ERFE) is an erythroid hormone putatively involved in stress erythropoiesis. Its regional clearance and circulating form in humans, as well as levels in normal health and coronary disease remain unclear.

METHODS

To establish a reference interval, ERFE was measured in 155 healthy volunteers using the Intrinsic LifeSciences ELISA. To identify trans-organ gradients in ERFE, regional blood sampling was undertaken in patients (n = 13) undergoing clinically indicated cardiac catheterisation. The Intrinsic ELISA was assessed for reproducibility, stability, linearity and possible cross-reactivity, interference and anticoagulant effects. Circulating forms of ERFE were evaluated by HPLC.

RESULTS

In healthy individuals, the median concentration of ERFE was 0.51 ng/mL (IQR: 0.12-1.25), with men (n = 78) having higher levels than women (n = 77) (0.67 vs 0.32 ng/mL, p = 0.0001). ERFE concentrations in trans-organ sampling revealed no clear organ of clearance or production. Samples with high endogenous ERFE levels were suppressed by haemoglobin (≥2 g/L), bilirubin (≥200 µmol/L), lipaemia (>1 g/L), and freeze thawing (≥2 cycles), but this was not observed with low ERFE concentrations. Endogenous ERFE immunoreactivity was 46% higher in EDTA plasma compared with serum and lithium heparin plasma. On SE-HPLC, ERFE eluted as intact and cleaved forms.

CONCLUSION

We provide a useful reference range for ERFE in EDTA plasma. We found no specific site of secretion or clearance. The Intrinsic ELISA performed adequately but is limited by interference and stability when endogenous levels are high. Circulating forms are multiple and complex.

Cardiovascular effects of DWORF (dwarf open reading frame) peptide in normal and ischaemia/reperfused isolated rat hearts

The novel peptide dwarf open reading frame (DWORF), highly conserved across species and expressed almost exclusively in cardiac ventricular muscle, may play a role in cardiac physiology and pathophysiology. The effect of direct administration of DWORF in the intact heart has not previously been examined. Accordingly, we investigated the cardiac effects of DWORF (1-30 nM) in normal isolated perfused rat hearts and hearts undergoing ischaemia/reperfusion (I/R) injury, and evaluated potential mechanisms of action. Exogenous DWORF at the top dose (30 nM) increased perfusion pressure (PP) in normal hearts, which indicates coronary vasoconstriction; and during post-ischaemic reperfusion, DWORF increased PP in a dose-dependent manner. In I/R hearts, DWORF at the top dose also increased left ventricular end-diastolic pressure and maximum and minimum derivatives of left ventricular pressure noted dP/dt(max) and dP/dt(min), respectively, without affecting developed pressure (DP). Co-infusion of DWORF with Diltiazem, an l-type Ca²⁺ channel blocker (1μM), in I/R hearts attenuated the falls in DP, dP/dt(max) and dP/dt(min) observed with Diltiazem alone. DWORF co-infusion with both Diltiazem and Y27632 (1μM) (a Rho-Kinase inhibitor) reversed the coronary vasodilator effect of the inhibitors administered alone. In conclusion, we provide the first evidence that DWORF has coronary vasoconstrictor actions in normal hearts and when administered during reperfusion in an ex-vivo model of cardiac I/R injury, and also exhibits positive cardiac inotropic activity in the latter setting. DWORF's effect on ventricular contractile function appears to be dependent on the l-type Ca²⁺ channel, whereas Rho-Kinase activity may be related to the coronary vasoconstrictor effects of DWORF.

150 ProBNP glycosylation of threonine 71 is increased with obesity in patients with heart failure

Funding Acknowledgements

The National Heart Foundation of New Zealand

Background

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Plasma levels of B-type natriuretic peptide (BNP) or its amino terminal congener (NT-proBNP) are used for HF diagnosis and risk stratification.  Circulating levels of both BNP and NT-proBNP are reduced by obesity and this phenomenon is one of the key weaknesses of the diagnostic performance of the natriuretic peptides in HF.  Formation of BNP from enzymatic cleavage of proBNP1-108 between residues 76 and 77 by corin and/or furin is influenced by the degree of proBNP glycosylation, therefore we investigated the relationship between proBNP glycosylation, plasma NT-proBNP and body mass index (BMI) in HF patients.

Methods

Three assays were developed to distinguish between total proBNP (glycosylated plus non-glycosylated proBNP), proBNP not glycosylated at threonine 71 (NG-T71) and proBNP not glycosylated in the central region (NG-C). Intra and inter-assay CVs were &lt;15%, limits of detection were &lt;2 pmol/L and samples diluted in parallel.

Results

Applying these assays and an NT-proBNP assay to plasma samples from 106 healthy volunteers and 238 patients with HF determined that concentrations (median(IQR)) of proBNP, NG-T71 and NT-proBNP were greater in HF patients compared to controls (24.9 (3.6-55), 9.4 (1.5-21) and 212 (104-409) pmol/L vs 3.0 (1.5-19), 3.0 (1.5-14.5) and 4.7 (2-8) pmol/L respectively, all p &lt; 0.012).  NG-C was undetectable in most samples. ProBNP levels in HF patients with BMI above and below 30 kg/m2 were not different (21.9 (2.6-70) pmol/L and 25.7 (3.9-53) pmol/L respectively, p = 0.85), whereas HF patients with BMI &gt; 30 had lower NT-proBNP and NG-T71 levels (121 (64-248) and 3 (1.5-16) pmol/L verse 271 (178-486) and 13.5 (1.5-24.2) pmol/L respectively, p &lt; 0.003) and higher proBNP:NT-proBNP and proBNP:NG-T71 ratios  (p = 0.001 and p = 0.02 respectively) than those with BMI &lt; 30.

Discussion and Conclusion

Using three new assays specific for different glycosylated forms of proBNP we have shown that the processing of proBNP is dysregulated in heart failure compared to controls due to increased glycosylation at threonine 71 of proBNP.  Obese patients with HF have even greater dysregulation, demonstrated by decreased concentrations of proBNP that is not glycosylated at T71 (NG-T71), and concomitant decreases in NT-proBNP.  Thus, we have shown for the first time that increased BMI is associated with increased proBNP glycosylation at T71 in patients with heart failure.  Glycosylation-induced impairment of proBNP processing explains, at least in part, the reduction in plasma concentrations of B-type cardiac natriuretic peptides observed in obesity. Using these assays to evaluate the proBNP profile of larger patient cohorts will further develop understanding of the relationships between BNP production, BMI and heart failure pathogenesis, which would be expected to lead to increased diagnostic performance.

Validity of a Novel Point-of-Care Troponin Assay for Single-Test Rule-Out of Acute Myocardial Infarction

Importance

Emergency department (ED) investigations of patients with suspected acute myocardial infarction (AMI) are time consuming, partly because of the turnaround time of laboratory tests. Current point-of-care troponin assays shorten test turnaround times but lack precision at lower concentrations. Development of point-of-care troponin assays with greater analytical precision could reduce the decision-making time in EDs for ruling out AMI.

Objective

To determine the clinical accuracy for AMI of a single troponin concentration measured on arrival to ED with a new-generation, higher precision point-of-care assay with a 15-minute turnaround time.

Design, Setting, and Participants

This observational study occurred at a single urban regional ED. Adults presenting acutely from the community to the ED with symptoms suggestive of AMI were included. Troponin concentrations were measured on ED arrival with both a novel point-of-care assay (i-STAT TnI-Nx; Abbott Point of Care) and a high-sensitivity troponin I assay (Architect hs-cTnI; Abbott Diagnostics).

Main Outcomes and Measures

The primary outcome was type 1 AMI during index presentation. We compared the discrimination ability of the TnI-Nx assay with the hs-cTnI assay using the area under receiver operator characteristic curve (AUC) and sensitivity, negative predictive value, and the proportion of negative test results at thresholds with 100% sensitivity.

Results

Of 354 patients (255 [72.0%] men; mean [SD] age, 62 [12] years), 57 (16.1%) experienced an AMI. Eighty-five patients (24.0%) presented to the ED less than 3 hours after symptom onset. No difference was found between the AUC of the TnI-Nx assay (0.975 [95% CI, 0.958-0.993]) and the hs-cTnI assay (0.970 [95% CI, 0.949 to 0.990]; P = .46). A TnI-Nx assay result of less than 11 ng/L identified 201 patients (56.7%) as low risk, with a sensitivity of 100% (95% CI, 93.7%-100%) and a negative predictive value of 100% (95% CI, 98.2%-100%). In comparison, an hs-cTnI assay result of less than 3 ng/L identified 154 patients (43.5%) as low risk, with a sensitivity of 100% (95% CI, 93.7%-100%) and a negative predictive value of 100% (95% CI, 97.6%-100%).

Conclusions and Relevance

A novel point-of-care troponin assay that can produce a result 15 minutes after blood sampling had comparable discrimination ability to an hs-cTnI assay for ruling out AMI after a single blood test. Use in the ED may facilitate earlier decision making and could expedite the safe discharge of a large proportion of low-risk patients.

P1756The protein APRIL predicts adverse outcomes in DAPT patients better than NT-proBNP and troponin

Aim

Dual antiplatelet therapy (DAPT) is a mainstay of post-ACS treatment. However, prediction of adverse events in these patients needs improving. We show here that the TNFα-related protein APRIL (which is produced in platelets and atherosclerotic plaque) is a superior predictor of MACE and new MI in DAPT recipients post-ACS.

Methods

We prospectively recruited 518 patients presenting with the primary complaint of acute chest pain to our hospital ED. Patients were adjudicated to have ACS by 2 independent cardiologists in accordance with ESC guidelines with hsTnI as biomarker. Plasma EDTA samples taken at presentation and 2 hours after were interrogated for APRIL measurements using a two site ELISA. Clinical data/variables, standard biochemistry analytes, hsTnT and NT-proBNP were also measured. Statistical assessments were made using SPSS v23 (IBM). Data for all biomarkers were treated as continuous variables and are presented as median (interquartile range, (IQR)). Statistical assessment of the comparative diagnostic abilities of APRIL, hsTnT, NT-proBNP and hsTnI were assessed using receiver operator curve (ROC) area under the curve (AUC) analysis. The comparative power of each biomarker (log values) to predict new MACE, MI, bleeding and mortality in 1) the whole group and in 2) DAPT recipients alone, within 2 yrs of index presentation was undertaken using a logistic regression base model (95% CI) that included all clinical variables and hsTnI and hsTnT, with APRIL and NT-proBNP each included in additional multivariate analyses.

Results

Of the 518 recruited patients (median age 63 (IQR: 54–73, 35% female), 152 were adjudicated to have ACS (29%, 115 MI, 37 UAP). Presentation APRIL levels were higher in those with a cardiac versus non-cardiac cause for presentation (3.0, (2.0–4.7) vs. 2.4, (1.6–3.8) ng/mL, P=0.001) and positively correlated with hsTnT and NT-proBNP (all P<0.001), but it did not add to the hsTnI (ROC = 0.96) or hsTnT (ROC =0.92) assisted diagnosis of ACS. In all 518 patients, in the multivariate regression model, APRIL was a significant independent predictor of mortality (n=54, P=0.032), new MI (n=43, P=0.006), new ADHF (n=24, P=0.016) and MACE (n=71, P=0.005) that was additive to NT-proBNP and troponin. In DAPT recipients alone (n=156), APRIL was the only biomarker to independently predict new MI (n=27, 95% CI: 1.125–3.982, P=0.020) and MACE (n=37, 95% CI: 1.058–3.389, P=0.031). None of the markers, only age, predicted bleeding episodes.

Conclusion

APRIL is an platelet/plaque derived marker that provides independent risk assessment in ACS patients. In DAPT recipients, the ability of APRIL to predict new MI and MACE is superior to that of cardiac troponins and NT-proBNP and could be used to identify high risk individuals.

Acknowledgement/Funding

Health Research Council of New Zealand; Heart Foundation of New Zealand

P3408The signal peptide of CNP is a novel predictor of MI, MACE and bleeding risk in chest pain patients

Aim

CNP is an important vascular and cardiac derived member of the natriuretic peptide family. We have previously provided the first reports that the signal peptide of CNP (CNPsp) is present in the human circulation and is elevated in those with chest pain suspicious of ACS. Here, show that CNPsp levels are highly predictive of new MI, MACE and post-index bleeding in patients presenting with potential ACS.

Methods

We prospectively recruited 493 patients presenting with the primary complaint of acute chest pain to our hospital ED. Patients were adjudicated as ACS by 2 independent cardiologists in accordance with ESC guidelines with hsTnI as biomarker. Plasma EDTA samples taken at presentation and 2 hours after were interrogated for CNPsp measurements using our validated, specific assay. Clinical data/variables, standard biochemistry analytes, hsTnT and NT-proBNP (both Roche Cobas e411) were also measured. Statistical assessments were made using SPSS v23. Data for all biomarkers were treated as continuous variables and are presented as median (interquartile range, (IQR)). Statistical assessment of the comparative abilities of CNPsp, hsTnT, NT-proBNP and hsTnI (log values) to predict new MACE, MI, bleeding and mortality within 2 yrs of index presentation was undertaken using a logistic regression base model (95% CI) that included all clinical variables and hsTnI and hsTnT and NT-proBNP, with CNPsp added to into the multivariate analyses.

Results

Of the 493 recruited patients (median age 63 (IQR: 54–73, 35% female), 148 were adjudicated to have ACS (30%, 109 MI, 39 UAP). Presentation CNPsp levels were not higher in those with adjudicated ACS versus non-ACS (51, (45–65) vs. 50, (42–63) pmol/L, P=0.412), did not correlate with hsTnI, hsTnT or NT-proBNP, but were significantly lower in those with a history of MI (49, (42–59) vs. 51, (43–64) pmol/L, P=0.044). In contrast, they were significantly higher in those with ECG ST-depression (56, (47–85) vs. 50 (42–62) pmol/L, P=0.038). In the multivariate regression model of all 493 patients, lower values of CNPsp were a significant multivariate predictor of new MI (n=37, 95% CI: 0.06–0.89, P=0.038), MACE (n=64, 95% CI: 0.08–0.81, P=0.020) and new bleeding (n=40, 95% CI: 0.05–0.63, P=0.005) within 2 years of presentation. This predictive ability was additive and independent from NT-proBNP and troponin.

Conclusion

This is the first report that CNPsp measurement provides meaningful and independent risk assessment of important outcomes in ACS patients. In particular, the fact that lower levels of CNPsp are predictive of negative MI, MACE and bleeding outcomes suggests that CNPsp may have an unappreciated protective role in the cardiovascular system.

Acknowledgement/Funding

Health Research Council of New Zealand; Heart Foundation of New Zealand

P2616Soluble urokinase plasminogen activator receptor (suPAR) predicts 1 year mortality in patients with acute breathlessness

Aim

Soluble urokinase plasminogen activator receptor (suPAR) is a pleotropic receptor, capable of orchestrating plaque vulnerability and vascular immune dysfunction. Its concentration in circulation may reflect on CVD associated burden. We examined the prognostic ability of suPAR to predict death in patients suspicious of ADHF.

Methods

suPAR measurements were undertaken with a CE-marked ELISA (ViroGates) in 444 patients presenting to hospital with the primary complaint of breathlessness to our hospital ED. A second sample at 12–48 hours post ED admission was available for 378 patients. Standard biochemistry analytes; MR-proADM (BRAHMS), NTproBNP and hsTnT (both Roche) were also measured. Statistical assessment was made using SPSS v25 (IBM), with all biomarkers treated as continuous variables and presented as median [interquartile range (IQR)]. Group comparisons were made by Mann-Whitney U test. The singular or combined clinical performances of suPAR, NT-proBNP, hsTnT and MR-proADM were assessed using receiver operator curve (ROC) area under the curve (AUC) (Z-scores) and Cox hazard regression (log-values) analyses. P-value <0.05 was considered significant.

Results

In the breathless cohort [median age 72 yrs (IQR: 62–81, 43% female)], 35.1% had ADHF and 94/444 patients died within the 1st yr of ED presentation. In those who died within this 1st yr, median suPAR concentrations at both time-points; 5.2 ng/mL (IQR: 2.8–5.5) vs. 5.1 ng/mL (IQR: 1.7–2.3) were higher than those who did not die (3.5 ng/mL; IQR: 2.7–5.1) (P<0.0001). Plasma suPAR, for both time points, respectively, could predict death at 30d (n=22, ROC-AUC = 0.77 and 0.76), 90d (n=41, ROC-AUC = 0.77 and 0.75) and 1 yr (ROC-AUC = 0.73 and 0.72). Improvement in 90d mortality prediction was achieved with the inclusion of suPAR in models; for e.g. using ED values, for NTproBNP; ROC-AUC of 0.67 increased to 0.71, for hsTnT; ROC-AUC of 0.69 to 0.76, and for MR-proADM, ROC-AUC of 0.72 to 0.75. Both suPAR time-points (ROC-AUC 0.70) could predict 1 yr new heart failure (HF) (n=68) but did not assist in improving HF prediction when used in combination with NT-proBNP, hsTnT or MR-proADM. After adjustment for conventional risk factors, Cox hazard regression analyses however revealed suPAR as the only biomarker capable of predicting 1 yr mortality (P=0.005) with hazard ratios of 2.8 (CI: 1.4–5.9) and 3.5 (CI: 1.1–11.3) for the ED and inpatient time-points, respectively. In terms of best window for prognostic assessment, suPAR concentrations at ED, outperformed the inpatient concentrations as the superior time-point in predicting 1 yr mortality.

Conclusion

suPAR exhibits excellent prognostic ability in mortality prediction, proving better than NTproBNP, hsTnT and MR-proADM in acutely breathless patients. The usage of suPAR in complementary with current candidate cardiac biomarkers could dramatically improve the prognostic tools available to guide risk management in HF.

Acknowledgement/Funding

New Zealand Heart Foundation, Health Research Council of New Zealand

Analytical, biochemical and clearance considerations of soluble urokinase plasminogen activator receptor (suPAR) in healthy individuals

BACKGROUND

Soluble urokinase plasminogen activator receptor (suPAR) is an emerging marker of cardiovascular disease burden. Appropriate assessment of assay performance and reference interval are required to enable interpretation of results to facilitate its clinical application.

METHODS

suPAR was measured using the suPARnostic® ELISA in 155 healthy volunteers. Assay performance was assessed for anticoagulant effect, recovery, interference, linearity and cross-reactivity. The identity of immunoreactive suPAR was confirmed by size-exclusion HPLC. To establish anatomical sites of release and uptake, we measured suPAR in regional samples from subjects undergoing cardiac catheterization.

RESULTS

The median concentration of suPAR was 2.1 ng/mL (IQR:1.7-2.3) in health. In comparison with EDTA, suPAR measurements were affected by lithium heparin (>10% change) and increased with serum usage. suPAR reactivity also increased in the presence of haemolysis (10 g/L), but was suppressed with urokinase and lipids (4 g/L). In multiple regression analyses, suPAR associated independently with body weight, NT-proBNP and MR-proADM (P = .03) for healthy individuals. Regional plasma sampling showed lower suPAR concentrations in the coronary sinus and renal vein compared with concentrations in femoral arterial samples. Immunoreactive circulating suPAR species had M_r of 10-39 kDa.

CONCLUSION

The suPARnostic® assay performs acceptably for a clinical assay but is limited in the presence of high levels of hemolysis, lipids and urokinase. We provide the first evidence for the heart and kidneys as organs of suPAR clearance in humans. Additional investigations are warranted to determine whether there is a need to compare the marker performance of differing circulating forms of suPAR.

ProBNP That Is Not Glycosylated at Threonine 71 Is Decreased with Obesity in Patients with Heart Failure

BACKGROUND

Heart failure (HF) is a leading cause of morbidity and mortality worldwide. Plasma concentrations of B-type natriuretic peptide (BNP) or its amino terminal congener (NT-proBNP) are used for HF diagnosis and risk stratification. Because BNP concentrations are inexplicably lowered in obese patients, we investigated the relationship between proBNP glycosylation, plasma NT-proBNP, and body mass index (BMI) in HF patients.

METHODS

Three assays were developed to distinguish between total proBNP (glycosylated plus nonglycosylated proBNP), proBNP not glycosylated at threonine 71 (NG-T71), and proBNP not glycosylated in the central region (NG-C). Intraassay and interassay CVs were <15%; limits of detection were <21 ng/L; and samples diluted in parallel.

RESULT

Applying these assays and an NT-proBNP assay to plasma samples from 106 healthy volunteers and 238 HF patients determined that concentrations [median (interquartile range)] of proBNP, NG-T71, and NT-proBNP were greater in HF patients compared with controls [300 (44-664), 114 (18-254), and 179 (880-3459) ng/L vs 36 (18-229), 36 (18-175), and 40 (17-68) ng/L, respectively; all P < 0.012]. NG-C was undetectable in most samples. ProBNP concentrations in HF patients with BMI more or less than 30 kg/m² were not different (P = 0.85), whereas HF patients with BMI >30 kg/m² had lower NT-proBNP and NG-T71 concentrations (P < 0.003) and higher proBNP/NT-proBNP and proBNP/NG-T71 ratios (P = 0.001 and P = 0.02, respectively) than those with BMI <30 kg/m².

CONCLUSIONS

Increased BMI is associated with decreased concentrations of proBNP not glycosylated at T71. Decreased proBNP substrate amenable to processing could partially explain the lower NT-proBNP and BNP concentrations observed in obese individuals, including those presenting with HF.

Detectable High-Sensitivity Cardiac Troponin within the Population Reference Interval Conveys High 5-Year Cardiovascular Risk: An Observational Study

BACKGROUND

Increased cardiac troponin I or T detected by high-sensitivity assays (hs-cTnI or hs-cTnT) confers an increased risk of adverse prognosis. We determined whether patients presenting with putatively normal, detectable cTn concentrations [> limit of detection and < upper reference limit (URL)] have increased risk of major adverse cardiovascular events (MACE) or all-cause mortality.

METHODS

A prospective 5-year follow-up of patients recruited in the emergency department with possible acute coronary syndrome (ACS) and cTn concentrations measured with hs-cTnI (Abbott) and hs-cTnT (Roche) assays. Cox regression models were generated with adjustment for covariates in those without MACE on presentation. Hazard ratios (HRs) for hs-cTn were calculated relative to the HRs at the median concentration.

RESULTS

Of 1113 patients, 836 were without presentation MACE. Of these, 138 incurred a MACE and 169 died during a median 5.8-year follow-up. HRs for MACE at the URLs were 2.3 (95% CI, 1.7-3.2) for hs-cTnI and 1.8 (95% CI, 1.3-2.4) for hs-cTnT. Corresponding HRs for mortality were 1.7 (95% CI, 1.2-2.2) for hs-cTnI and 2.3 (95 % CI, 1.7-3.1) for hs-cTnT. The HR for MACE increased with increasing hs-cTn concentration similarly for both assays, but the HR for mortality increased at approximately twice the rate for hs-cTnT than hs-cTnI. Patients with hs-cTnI ≥10 ng/L or hs-cTnT ≥16 ng/L had the same percentage of MACE at 5-year follow-up (33%) as patients with presentation MACE.

CONCLUSIONS

Many patients with ACS ruled out and putatively normal but detectable hs-cTnI concentrations are at similar long-term risk as those with MACE. hs-cTnT concentrations are more strongly associated with 5-year mortality than hs-cTnI.

B-Type Natriuretic Peptide Forms within the Heart, Coronary Sinus, and Peripheral Circulation in Humans: Evidence for Degradation before Secretion

BACKGROUND

The B-type natriuretic peptides (BNP and N-terminal pro-BNP) are secreted by the heart and, in the case of BNP, serve to maintain circulatory homeostasis through renal and vascular actions and oppose many effects of the renin-angiotensin system. Recent evidence suggests that in patients with severe heart failure, circulating immunoreactive BNP is made up mainly of metabolites that may have reduced bioactivity. We hypothesized that BNP may be degraded before it even leaves the heart.

METHODS

Peripheral venous plasma plus atrial and ventricular tissue, obtained from explanted hearts at the time of transplantation, were collected from 3 patients with end-stage heart failure. In a separate study, plasma was collected from the coronary sinus and femoral artery of 3 separate patients undergoing cardiac catheterization. Plasma C18 reverse-phase extracts were separated on reverse-phase HPLC, and the collected fractions were subjected to RIAs with highly specific antisera directed to the amino- and carboxy-terminal ends of BNP(1–32).

RESULTS

ProBNP, BNP(1–32), and 2 major BNP metabolites were present in atrial and ventricular tissue, where BNP(1–32) represented 45% and 70% of total processed BNP, respectively. Neither BNP(1–32) nor the 2 metabolites were detected in peripheral venous plasma. Nor was BNP(1–32) detected in matching coronary sinus and femoral artery plasma from the 3 patients undergoing cardiac catheterization.

CONCLUSIONS

BNP(1–32) is partly degraded within the hearts of patients with end-stage heart failure, and even in patients with relatively well-preserved left ventricular systolic function, only BNP metabolites enter the systemic circulation.

Validation of high-sensitivity troponin I in a 2-hour diagnostic strategy to assess 30-day outcomes in emergency department patients with possible acute coronary syndrome

OBJECTIVES

The study objective was to validate a new high-sensitivity troponin I (hs-TnI) assay in a clinical protocol for assessing patients who present to the emergency department with chest pain.

BACKGROUND

Protocols using sensitive troponin assays can accelerate the rule out of acute myocardial infarction in patients with low-risk (suspected) acute coronary syndrome (ACS).

METHODS

This study evaluated 2 prospective cohorts of patients in the emergency department with ACS in an accelerated diagnostic pathway integrating 0- and 2-h hs-TnI results, Thrombolysis In Myocardial Infarction (TIMI) risk scores, and electrocardiography. Strategies to identify low-risk patients incorporated TIMI risk scores= 0 or ≤ 1. The primary endpoint was a major adverse cardiac event (MACE) within 30 days.

RESULTS

In the primary cohort, 1,635 patients were recruited and had 30-day follow-up. A total of 247 patients (15.1%) had a MACE. The finding of no ischemic electrocardiogram and hs-TnI ≤ 26.2 ng/l with the TIMI = 0 and TIMI ≤ 1 pathways, respectively, classified 19.6% (n = 320) and 41.5% (n = 678) of these patients as low risk; 0% (n = 0) and 0.8% (n = 2) had a MACE, respectively. In the secondary cohort, 909 patients were recruited. A total of 156 patients (17.2%) had a MACE. The TIMI = 0 and TIMI ≤ 1 pathways classified 25.3% (n = 230) and 38.6% (n = 351), respectively, of these patients as low risk; 0% (n = 0) and 0.8% (n = 1) had a MACE, respectively. Sensitivity, specificity, and negative predictive value for TIMI = 0 in the primary cohort were 100% (95% confidence interval [CI]: 98.5% to 100%), 23.1% (95% CI: 20.9% to 25.3%), and 100% (95% CI: 98.8% to 100%), respectively. Sensitivity, specificity, and negative predictive value for TIMI ≤ 1 in the primary cohort were 99.2 (95% CI: 97.1 to 99.8), 48.7 (95% CI: 46.1 to 51.3), and 99.7 (95% CI: 98.9 to 99.9), respectively. Sensitivity, specificity, and negative value for TIMI ≤ 1 in the secondary cohort were 99.4% (95% CI: 96.5 to 100), 46.5% (95% CI: 42.9 to 50.1), and 99.7% (95% CI: 98.4 to 100), respectively.

CONCLUSIONS

An early-discharge strategy using an hs-TnI assay and TIMI score ≤ 1 had similar safety as previously reported, with the potential to decrease the observation periods and admissions for approximately 40% of patients with suspected ACS. (Advantageous Predictors of Acute Coronary Syndromes Evaluation [APACE] Study, NCT00470587; A 2 hr Accelerated Diagnostic Protocol to Assess patients with chest Pain symptoms using contemporary Troponins as the only biomarker [ADAPT]: a prospective observational validation study, ACTRN12611001069943).

Oxidative stress rather than triglyceride accumulation is a determinant of mitochondrial dysfunction in in vitro models of hepatic cellular steatosis

BACKGROUND/AIMS

There is still debate about the relationship between fat accumulation and mitochondrial function in nonalcoholic fatty liver disease. It is a critical question as only a small proportion of individuals with steatosis progress to steatohepatitis. In this study, we focused on defining (i) the effects of triglyceride accumulation and reactive oxygen species (ROS) on mitochondrial function (ii) the contributions of triglyceride, ROS and subsequent mitochondrial impairment on the metabolism of energy substrates.

METHODS

Human hepatoblastoma C3A cells, were treated with various combinations of oleate, octanoate, lactate (L), pyruvate (P) and ammonia (N) acutely or for 72 h, before measurements of triglyceride concentration, cell respiration, ROS production, mitochondrial membrane potential, ketogenesis and gluconeogenesis, TCA cycle metabolite analysis and electron microscopy.

RESULTS

Acutely, LPON treatment enhanced mitochondrial respiration and ROS formation. After 72 h, despite the similarities in triglyceride accumulation, LPON treatment, but not oleate, dramatically affected mitochondrial function as evidenced by decreased respiration, increased mitochondrial membrane potential and ROS formation with concomitant enhanced ketogenesis. By comparison, respiration and ROS formation remained unperturbed with oleate. Importantly, this was accompanied by an increased gluconeogenesis and ketogenesis. The addition of the antioxidant N-acetyl-L-cysteine prevented mitochondrial dysfunction and reversed metabolic changes seen with LPON, strongly suggesting ROS involvement in mediating mitochondrial impairment.

CONCLUSIONS

Our data indicate that ROS formation, rather than cellular steatosis per se, impairs mitochondrial function. Thus, reduction in cellular steatosis may not always be the desired outcome without concomitant improvement in mitochondrial function and/or reducing of ROS formation.

B-type natriuretic peptides: looking to the future

Whereas the role of the cardiac natriuretic peptides, ANP and BNP, in some aspects of physiology and pathophysiology is clear, their potential in diagnosis, prognosis, and therapeutics in many clinical disorders remains uncertain. We predict that circulating levels of these peptides will find increasing diagnostic utility in patients presenting with dyspnoea, in guiding the complex pharmacotherapy in heart failure, and may likewise be useful in guiding the management of patients on chronic maintenance renal dialysis. We predict also that levels of these peptides will be of practical use as prognostic indicators in 'at-risk' populations (such as those with diabetes, coronary heart disease, hypertension, thalassaemia, etc.) but probably not in the general population. It appears likely that administration of these peptides will find a place in the therapeutics of acute myocardial infarction, but this is less clear for heart failure. We describe the presence of a segment of the signal peptide for BNP within the circulation and discuss its potential clinical utility.

Regional vascular response to ProAngiotensin-12 (PA12) through the rat arterial system

ProAngiotensin-12 (PA12) is the most recent peptide to be identified as a functional component of the renin-angiotensin system (RAS). PA12 is reported to constrict rat coronary arteries and the aorta, dependent upon angiotensin II-converting enzyme 1 (ACE1) and chymase. The current study employed myography to determine the direct vascular effects of PA12 on a range of isolated rat arteries extending from the core to periphery. PA12 significantly constricted the descending thoracic aorta, right and left common carotid arteries, abdominal aorta and superior mesenteric artery, with little effect on the femoral and renal arteries. AngII was found to produce similar responses to PA12 when administered at the same dose. A potency gradient in response to PA12 was clearly apparent, with vessels in closest proximity to the heart responding with the greatest constriction; while constrictive potency was lost further form the heart. Inhibition of ACE1 and chymase both significantly attenuated PA12-induced vasoconstriction, with chymostatin displaying lesser potency. We postulate ACE1 primarily regulates RAS activity within the circulation, while chymase may have an important role in local, tissue-based RAS activity.

Urotensin II and urotensin II-related peptide (URP) in cardiac ischemia-reperfusion injury

Circulating urotensin II (UII) concentrations and the tissue expression of its cognate receptor (UT) are elevated in patients with cardiovascular disease (CVD). The functional significance of elevated plasma UII levels in CVD is unclear. Urotensin-related peptide (URP) is a paralog of UII in that it contains the six amino acid ring structures found in UII. Although both peptides are implicated as bioactive factors capable of modulating cardiovascular status, the role of both UII and URP in ischemic injury is unknown. Accordingly, we provide here the first report describing the direct cardiac effects of UII and URP in ischemia-reperfusion injury. Isolated perfused rat hearts were subjected to no-flow global ischemia for 45 min after 30min preconditioning with either 1nM rUII or 10nM URP. Both rUII- and URP-induced significant vasodilation of coronary arteries before (both P<0.05) and after ischemia (both P<0.05). Rat UII alone lowered contractility prior to ischemia (P=0.053). Specific assay of perfusate revealed rUII and URP both significantly inhibited reperfusion myocardial creatine kinase (CK) release (P=0.012 and 0.036, respectively) and atrial natriuretic peptide (ANP) secretion (P=0.025). Antagonism of the UT receptor with 1muM palosuran caused a significant increase in perfusion pressure (PP) prior to and post-ischemia. Furthermore, palosuran significantly inhibited reductions in both PP and myocardial damage marker release induced by both rUII and URP. In conclusion, our data suggests rUII and URP reduce cardiac ischemia-reperfusion injury by increasing flow through the coronary circulation, reducing contractility and therefore myocardial energy demand, and inhibiting reperfusion myocardial damage. Thus, UII and URP present as novel peptides with potential cardioprotective actions.

Urocortin 2 infusion in human heart failure

AIMS

To document the haemodynamic, neurohormonal, and renal responses to Urocortin 2 (UCN2) infused in human heart failure (HF).

METHODS AND RESULTS

Eight male patients with HF [left ventricular ejection fraction (LVEF) < 40%, NYHA class II-III] received placebo and 25 [low dose (LD)] and 100 microg [high dose (HD)] of UCN2 intravenously over 1 h in a single-blind, placebo-controlled, dose-escalation design. UCN2 increased cardiac output (CO) (mean peak increments +/- SEM; placebo 0.3 +/- 0.1; LD 1.0 +/- 0.3; HD 2.0 +/- 0.2 L/min; P < 0.001) and LVEF (0.0 +/- 1.5; LD 5.9 +/- 2.1; HD 14.1 +/- 2.7%; P = 0.001) and decreased mean arterial pressure (placebo 6.7 +/- 1.3; LD 11.4 +/- 1.7; HD 19.4 +/- 3.3 mmHg; P = 0.001), systemic vascular resistance (SVR) (placebo 104 +/- 37; LD 281 +/- 64; HD 476 +/- 79 dynes s/cm(5); P < 0.003), and cardiac work (CW) (placebo 48 +/- 12; LD 66 +/- 22; HD 94 +/- 13 mmHg/L/min; P < 0.001). No significant effect on vasoconstrictor/volume-retaining neurohormones was noted. UCN2 decreased urinary volume (P = 0.035) but not creatinine excretion (P = 0.962).

CONCLUSION

Intravenous UCN2 in HF induced increases in CO and LVEF with falls in SVR and CW. No hormone response occurred. The role of UCN2 in circulatory regulation and its potential therapeutic application in heart disease warrant further investigation.

Urocortin 2 infusion in healthy humans: hemodynamic, neurohormonal, and renal responses

OBJECTIVES

We sought to examine the effects of urocortin (UCN) 2 infusion on hemodynamic status, cardiovascular hormones, and renal function in healthy humans.

BACKGROUND

Urocortin 2 is a vasoactive and cardioprotective peptide belonging to the corticotrophin-releasing factor peptide family. Recent reports indicate the urocortins exert important effects beyond the hypothalamo-pituitary-adrenal axis upon cardiovascular and vasohumoral function in health and cardiac disease.

METHODS

We studied 8 healthy unmedicated men on 3 separate occasions 2 to 5 weeks apart. Subjects received placebo, 25-microg low-dose (LD), and 100-microg high-dose (HD) of UCN 2 intravenously over the course of 1 h in a single-blind, placebo-controlled, dose-escalation design. Noninvasive hemodynamic indexes, neurohormones, and renal function were measured.

RESULTS

The administration of UCN 2 dose-dependently increased cardiac output (mean peak increments +/- SEM) (placebo 0.5 +/- 0.2 l/min; LD 2.1 +/- 0.6 l/min; HD 5.0 +/- 0.8 l/min; p < 0.001), heart rate (placebo 3.3 +/- 1.0 beats/min; LD 8.8 +/- 1.8 beats/min; HD 17.8 +/- 2.1 beats/min; p < 0.001), and left ventricular ejection fraction (placebo 0.6 +/- 1.4%; LD 6.6 +/- 1.5%; HD 14.1 +/- 0.8%; p < 0.001) while decreasing systemic vascular resistance (placebo -128 +/- 50 dynes x s/cm(5); LD -407 +/- 49 dynes x s/cm(5); HD -774 +/- 133 dynes.s/cm(5); p < 0.001). Activation of plasma renin activity (p = 0.002), angiotensin II (p = 0.001), and norepinephrine (p < 0.001) occurred only with the higher 100-mug dose. Subtle decreases in urine volume (p = 0.012) and natriuresis (p = 0.001) were observed.

CONCLUSIONS

Brief intravenous infusions of UCN 2 in healthy humans induced pronounced dose-related increases in cardiac output, heart rate, and left ventricular ejection fraction while decreasing systemic vascular resistance. Subtle renal effects and activation of plasma renin, angiotensin II, and norepinephrine (at high-dose only) were observed. These findings warrant further investigation of the role of UCN 2 in circulatory regulation and its potential therapeutic application in heart disease.

Cardiovascular effects of native and non-native urotensin II and urotensin II-related peptide on rat and salmon hearts

Urotensin II (UII) was first discovered in the urophyses of goby fish and later identified in mammals, while urotensin II-related peptide (URP) was recently isolated from rat brain. We studied the effects of UII on isolated heart preparations of Chinook salmon and Sprague-Dawley rats. Native rat UII caused potent and sustained, dose-dependent dilation of the coronary arteries in the rat, whereas non-native UII (human and trout UII) showed attenuated vasodilation. Rat URP dilated rat coronary arteries, with 10-fold less potency compared with rUII. In salmon, native trout UII caused sustained dilation of the coronary arteries, while rat UII and URP caused significant constriction. Nomega-nitro-(l)-arginine methyl (l-NAME) and indomethacin significantly attenuated the URP and rat UII-induced vasodilation in the rat heart. We conclude that UII is a coronary vasodilator, an action that is species form specific. We also provide the first evidence for cardiac actions of URP, possibly via mechanisms common with UII.

Resistin worsens cardiac ischaemia-reperfusion injury

We provide the first report of direct effects of resistin upon haemodynamic and neurohumoral parameters in isolated perfused rat heart preparations. Pre-conditioning with 1 nmol L-1 recombinant human resistin prior to ischaemia significantly impaired contractile recovery during reperfusion, compared with vehicle-infused hearts (P<0.05, n=12). This was accompanied by a significant increase in both A-type and B-type natriuretic peptides (P<0.05, n=12 both ANP and BNP vs vehicle), creatine kinase, and tumour necrosis factor-alpha (TNF-alpha) release in resistin-infused hearts. Resistin had no significant effect on myocardial glucose uptake. Co-infusion of resistin with Bay 11 7082 (an NF-kappaB inhibitor) improved contractile recovery following ischaemia and reduced both natriuretic peptide and creatine kinase release. This is the first evidence indicating resistin impairs cardiac recovery following ischaemia, stimulates cardiac TNF-alpha secretion, and modulates reperfusion release of natriuretic peptides and biochemical markers of myocardial damage. A TNF-alpha signalling related mechanism is suggested as one component underlying these effects.

Effect of urocortin 1 infusion in humans with stable congestive cardiac failure

In sheep with HF (heart failure), Ucn1 (urocortin 1) decreases total peripheral resistance and left atrial pressure, and increases cardiac output in association with attenuation of vasopressor hormone systems and enhancement of renal function. In a previous study, we demonstrated in the first human studies that infusion of Ucn1 elevates corticotropin (‘ACTH’), cortisol and ANP (atrial natriuretic peptide), and suppresses the hunger-inducing hormone ghrelin in normal subjects. In the present study, we examined the effects of Ucn1 on pituitary, adrenal and cardiovascular systems in the first Ucn1 infusion study in human HF. In human HF, it is proposed that Ucn1 would augment corticotropin and cortisol release, suppress ghrelin and reproduce the cardiorenal effects seen in animals with HF. On day 3 of a controlled metabolic diet, we studied eight male volunteers with stable HF (ejection fraction <40%; New York Heart Association Class II–III) on two occasions, 2 weeks apart, receiving 50 μg of Ucn1 or placebo intravenously over 1 h in a randomized time-matched cross-over design. Neurohormones, haemodynamics and urine indices were recorded. Ucn1 infusion increased plasma Ucn1, corticotropin (baseline, 5.9±0.9 pmol/l; and peak, 7.2±1.0 pmol/l) and cortisol (baseline, 285±42 pmol/l; and peak, 310±41 pmol/l) compared with controls (P<0.001, 0.008 and 0.047 respectively). The plasma Ucn1 half-life was 54±3 min. ANP and ghrelin were unchanged, and no haemodynamic or renal effects were seen. In conclusion, a brief intravenous infusion of 50 μg of Ucn1 stimulates corticotropin and cortisol in male volunteers with stable HF.

Deconvolution analysis of cardiac natriuretic peptides during acute volume overload

Cardiac natriuretic peptides, especially amino terminal pro-Brain Natriuretic Peptide (NT-proBNP), are emerging as powerful circulating markers of cardiac function. However, the in vivo secretion and elimination (t1/2) of these peptides during acute volume overload have not been studied. We present the first report of the secretion and elimination of cardiac natriuretic peptides, based on deconvolution analysis of endogenous ovine plasma levels measured by specific radioimmunoassay. Four normal, conscious sheep underwent rapid right ventricular pacing (225 bpm) for 1 hour to stimulate acute cardiac natriuretic peptide release. Plasma samples and right atrial pressure measurements were taken at regular intervals 30 minutes before, during, and 4 hours after pacing. Baseline right atrial pressure significantly increased (P:=0.02) during the 1 hour of pacing in association with a prompt increase in plasma BNP (P:=0.03), atrial natriuretic peptide (P:=0.01), and NT-proBNP (P:=0.02). Deconvolution analysis showed that the t1/2 of NT-proBNP (69.6+/-10.8 minutes) was 15-fold longer than BNP (4.8+/-1. 0 minutes). Despite sustained increases in atrial pressure, cardiac secretion of natriuretic peptides (particularly atrial natriuretic peptide) fell during the pacing period, suggesting a finite source of peptide for secretion. Size-exclusion high-performance liquid chromatography revealed NT-proBNP to be a single immunoreactive peak, whereas BNP comprised at least 2 immunoreactive forms. These findings, especially the prompt secretion of BNP and the prolonged t1/2 of NT-proBNP, clarify the metabolism of BNP forms and help to explain the diagnostic value of NT-proBNP measurement as a sensitive marker of ventricular function.

Neurohormones in an ovine model of compensated postinfarction left ventricular dysfunction

Clinical heart failure, often the result of myocardial infarction, may be preceded by a period of compensated left ventricular impairment. There is substantial need for an experimental model that reflects this human condition. In sheep, coronary artery ligation produced consistent left ventricular anteroapical myocardial infarctions resulting in chronic (5 wk), stable hemodynamic changes compared with sham controls, including reductions in ejection fraction (51 +/- 2 vs. 30 +/- 5%, P < 0.001), cardiac output (6.3 +/- 0.2 vs. 5.1 +/- 0.2 l/min, P < 0.01), and arterial pressure (93 +/- 2 vs. 79 +/- 3 mmHg, P < 0.001), and increases in cardiac preload (left atrial pressure, 3.3 +/- 0.1 vs. 8.3 +/- 1.3 mmHg, P < 0.001). These changes were associated with acute and sustained increases in plasma concentrations of atrial natriuretic peptide (ANP; 5 wk, 11 +/- 2 vs. 27 +/- 5 pmol/l, P < 0.001), brain natriuretic peptide (BNP; 3 +/- 0.2 vs. 11 +/- 2 pmol/l, P < 0.001), and amino-terminal pro-brain natriuretic peptide (NT-BNP; 17 +/- 3 vs. 42 +/- 12 pmol/l, P < 0.001). Significant correlations were observed between plasma levels of the natriuretic peptides (ANP, day 7 to week 5 samples; BNP and NT-BNP, day 1 to week 5 samples) and changes in left ventricular volumes and ejection fraction. In contrast, renin activity, aldosterone, catecholamines, and endothelin were not chronically elevated postinfarction and were not related to indexes of ventricular function. Coronary artery ligation in sheep produces the pathological, hemodynamic, and neurohormonal characteristics of compensated left ventricular impairment secondary to myocardial infarction. Plasma concentrations of the cardiac natriuretic peptides are sensitive markers of left ventricular dysfunction. This is a reproducible model that reflects the clinical condition and should prove suitable for investigating the pathophysiology of, and experimental therapies in, early left ventricular dysfunction.

Amino-terminal proBNP in ovine plasma: evidence for enhanced secretion in response to cardiac overload

We have recently identified a novel amino-terminal fragment of pro-brain natriuretic peptide (NT-proBNP) in the circulation of humans, the concentration of which increases progressively as the left ventricle fails. To clarify the origins of NT-proBNP in experimental animals, we have developed an RIA for NT-proBNP based on residues 52-71 of ovine proBNP-(1-103) and used it to study cardiac processing, secretion, and metabolism of BNP in sheep with cardiac overload induced by coronary artery ligation (CAL) or rapid left ventricular pacing (rLVP). The concentration of NT-proBNP in left atrial plasma extracts drawn from normal control sheep was threefold that of mature BNP. Size-exclusion and reverse-phase HPLC analyses of plasma extracts coupled to RIA revealed a single peak of immunoreactive (ir) NT-proBNP [ approximately 8,000 relative molecular weight (Mr)], quite distinct from a single peak of ir-mature BNP ( approximately 3,000 Mr). In contrast, ovine cardiac tissue contained only a single immunoreactive peak of high-molecular-weight BNP ( approximately 11,000 Mr), consistent in size with proBNP-(1-103). Sampling from the cardiac coronary sinus in normal control sheep (n = 5) and sheep with CAL (n = 5) revealed that the molar ratio of NT-proBNP to mature BNP was similar. There was a significant gradient of both mature and NT-proBNP across the heart in normal sheep, whereas after CAL the gradient was significant for mature BNP only. In both forms of cardiac overload (CAL and rLVP), left atrial plasma levels of NT-proBNP were significantly increased above normal levels, in contrast with mature BNP levels, which were raised only in the rLVP group of animals. Blockade of natriuretic peptide metabolism in sheep with heart failure (induced by rLVP) raised mature BNP levels threefold but did not affect levels of NT-proBNP. In conclusion, these studies show that NT-proBNP is formed from proBNP stores during secretion and, compared with mature BNP, accumulates in plasma because metabolism of NT-proBNP appears to differ from that of mature BNP. Although its function, if any, remains unclear, plasma NT-proBNP may prove to be a sensitive marker of cardiac overload and/or decompensation.

Ovine brain natriuretic peptide in cardiac tissues and plasma: effects of cardiac hypertrophy and heart failure on tissue concentration and molecular forms

Whereas numerous studies have examined the cardiac tissue content and secretion of atrial natriuretic peptide (ANP), the response of brain natriuretic peptide (BNP) in states of experimental cardiac overload is less well documented. Our recent partial cloning of the ovine BNP gene has enabled us to study changes in cardiac tissue concentration, together with tissue and circulating molecular forms of ANP and BNP, in response to cardiac overload induced by rapid ventricular pacing (n = 7) and aortic coarctation (n = 6). In normal sheep, although highest levels of BNP were found in atrial tissue (15-fold those of the ventricle), the BNP/ANP concentration ratio in the ventricles was 10- to 20-fold higher than the ratio calculated for atrial tissue. Compared with normal sheep, significant depletion of both ANP and BNP concentrations within the left ventricle occurred after rapid ventricular pacing. Size exclusion and reverse phase HPLC analysis of atrial and ventricular tissue extracts from normal and overloaded sheep showed a single peak of high molecular weight BNP consistent with the proBNP hormone. In contrast, immunoreactive BNP extracted from plasma drawn from the coronary sinus was all low molecular weight material. Further analysis of plasma BNP using ion exchange HPLC disclosed at least 3 distinct immunoreactive peaks consistent with ovine BNP forms 26-29 amino acid residues in length. These findings show that BNP is stored as the prohormone in sheep cardiac tissues and that complete processing to mature forms occurs at the time of secretion. The capacity to process the prohormone at secretion is not impaired by chronic heart failure.

Natriuretic peptides in sheep with pressure overload left ventricular hypertrophy

To examine tissue and plasma atrial (ANP) and brain natriuretic peptide (BNP) responses to left ventricular hypertrophy (LVH) 7 sheep underwent suprarenal aortic banding (20 mmHg initial pressure differential). Median survival time was 15 days. Proximal mean aortic pressure (MAP) increased from 65.1 +/- 5.0 mmHg (baseline) to 111.6 +/- 7.5 mmHg (day 7, p < 0.0001). Distal systolic aortic pressure fell from 85.5 +/- 8.7 mmHg (baseline) to 55.6 +/- 6.4 mmHg (day 7, p = 0.0002). Maximal plasma ANP (26.9 +/- 3.6 vs 10.1 +/- 1.2 pmol/L, p = 0.005) and BNP (15.3 +/- 3.6 vs. 3.5 +/- 1.0 pmol/L, p = 0.006) were recorded at 15 +/- 4.0 days. Coarctation induced rapid increases in PRA and plasma aldosterone and a fall in urinary sodium. Post-mortem examination of hearts confirmed LVH. Compared with controls, tissue ANP concentration was reduced in left atrium (p = 0.04) and LV (p = 0.04). BNP concentration was reduced in left atrium (p = 0.02) but tended to be higher in LV. In conclusion, suprarenal aortic coarctation leads to progressive hypertension resulting in LVH, progressive increases in plasma ANP and BNP and, in most cases, death from heart failure.

Single medial injection peribulbar anaesthesia using prilocaine

A prospective randomised study is reported comparing a single peribulbar injection into the medial compartment of the orbit and the standard two injection peribulbar technique. One hundred and seven patients undergoing elective intra-ocular surgery were randomly allocated to receive either a single medial injection, or two injections, using prilocaine 3% with felypressin. Akinesia and pain during surgery were assessed following the injection(s). There was no significant difference in pain during surgery and globe akinesia between the two groups. The single medial peribulbar injection is as effective as two injections using prilocaine 3%.

Peribulbar and retrobulbar anesthesia with prilocaine: a comparison of two methods of local ocular anesthesia

Prilocaine (Citanest) has been shown to be a satisfactory alternative to lignocaine, with certain important advantages, including superior diffusion. The latter may be especially important in peribulbar anesthesia, where the level of diffusion is a critical factor in providing a timely, high-quality block. In a prospective randomized study, we compared the effectiveness of peribulbar vs retrobulbar administration of prilocaine. Eighty-seven patients undergoing elective intraocular surgery were randomized to receive either retrobulbar or peribulbar anesthesia with prilocaine 3% with felypressin and hyaluronidase. Pain of injection, akinesia, and anesthesia were evaluated at predetermined intervals after injection. Except for the fact that lid akinesia occurred earlier in the peribulbar group, there was no difference in the quality or rate of onset of overall akinesia in the two groups. Nor were there any differences in the pain associated with injection. Both groups had excellent operative anesthesia and akinesia.