Highly Sensitive Cardiac Troponin T Values Remain Constant after Brief Exercise- or Pharmacologic-Induced Reversible Myocardial Ischemia

Predictors of Stress-Delta High-Sensitivity Troponin T in Emergency Department Patients Undergoing Stress Testing

Background and objective

Elevations in high-sensitivity troponin T (hs-TnT) are frequently observed following extreme physical exercise. In light of this, we sought to determine whether specific clinical characteristics are associated with this phenomenon in patients undergoing cardiac exercise tolerance testing (ETT).

Methods

We conducted a retrospective analysis of a prospectively collected biospecimen repository of 257 patients undergoing a stress echocardiogram for possible acute coronary syndrome (ACS). Ischemic electrocardiogram (ECG) changes during ETT and the presence or absence of ischemia on imaging were determined by a board-licensed cardiologist. N-terminal pro-brain natriuretic peptide (NT-proBNP) and hs-TnT assays were obtained immediately before and two hours following ETT. We developed linear regression models including several clinical characteristics to predict two-hour stress-delta hs-TnT. Variable selection was performed using the least absolute shrinkage and selection operator (LASSO).

Results

The mean age of the patients was 52 years [standard deviation (SD): 11.4]; 125 (48.6%) of them were men, and 88 (34.2%) were African-American. Twenty-two patients (8.6%) had ischemia evident on echocardiography, and 31 (12.1%) had ischemic ECG changes during exercise. The mean baseline hs-TnT was 5.6 ng/L (SD: 6.4) and the mean two-hour hs-TnT was 7.1 ng/L (SD: 10.2). Age and ischemic ECG changes were associated with two-hour stress-delta hs-TnT values.

Conclusions

Based on our findings, ischemic changes in stress ECG and age were associated with an increase in hs-TnT levels following exercise during a stress echo.

Myocardial injury in stress echocardiography: Comparison of dobutamine, dipyridamole and dynamic stressors-single center study

OBJECTIVES

In stress echocardiography (SE), dipyridamole (DIP) and dynamic stress (ExSE) are reported as being safer than dobutamine stress echocardiography (DSE). We investigated whether these commonly used stressors cause myocardial injury, measured by high sensitivity troponin T (hsTnT).

METHODS

One hundred and thirty five patients (DSE n = 46, ExsE n = 46, DIP n = 43) with negative result of SE were studied. The exclusion criteria were known ischaemic heart disease (IHD), baseline wall motion abnormalities, left ventricle systolic dysfunction/regional wall motion abnormalities, septum/posterior wall ≥13 mm, diabetes/pre-diabetes, baseline hsTnT level ≥14 ng/L, baseline blood pressure ≥160/100 mmHg, peak pulmonary pressure ≥45mmHg, eGFR <1ml/s/1.73m² , more than mild to moderate valvular disease and dobutamine side effects. HsTnT was measured before and 180 minutes after the test.

RESULTS

All patients had low pre-test probabilities of having obstructive IHD. HsTnT increased in DSE, less so in ExSE, and was unchanged in the DIP group (∆hsTnT 9.4 [1.5-58.6], 1.1 [-0.9-15.7], -0.1 [-1.4-2.1] ng/L, respectively, p<0.001). In DSE, the ∆hsTnT was associated with peak dobutamine dose (r = 0.30, p = 0.045), test length (r = 0.43, p = 0.003) and atropine use (p<0.001). In ExSE, the hsTnT increase was more likely in females (p = 0.012) and the elderly (>65 years) (r = 0.32, p = 0.03); no association was found between atropine use (p = 0.786) or test length and ∆hsTnT (r = 0.10, p = 0.530).

CONCLUSIONS

DSE is associated with myocardial injury in patients with negative SE, no injury was observed in DIP and only mild case in ExSE. Whether myocardial injury is causative of the higher reported adverse event rates in DSE remains to be determined.

Effect of Revascularization on Exercise-Induced Changes in Cardiac and Prothrombotic Biomarkers in Patients with Coronary Artery Disease

We examined whether resting levels and exercise-induced changes during exercise ECG stress test (EST) of cardiac Troponin T (cTnT), NT-proBNP and prothrombotic markers were affected by revascularization in patients with coronary artery disease (CAD).

EST1 was performed before coronary angiography and revascularization, and patients (n  =  20) with confirmed CAD, performed another EST (EST2) 9 weeks later. Blood samples were drawn at rest and within five min after termination of ESTs.

cTnT and NT-proBNP increased during exercise at both ESTs (p < 0.001, all). Resting cTnT levels at EST2 versus EST1 were significantly higher (p  =  0.02) whereas NT-proBNP did not differ. At both visits, increased D-dimer (p  =  0.008 and <0.001), pro-thrombin fragment 1  +  2 (p  =  0.009 and 0.001) and tissue factor pathway inhibitor (TFPI) (p < 0.001 and 0.001) during exercise were demonstrated. Resting levels of endogenous thrombin potential (ETP) and TFPI were reduced at EST2 versus EST1 (p < 0.01).

Revascularization did not affect exercise-induced release of cardiac and prothrombotic biomarkers and did not reduce resting levels of cTnT or NT-proBNP, suggesting revascularization per se not to prevent secretion of biomarkers. The lower resting levels of ETP and TFPI after revascularization may however, be indicative of reduced thrombin generation and endothelial activation.

Clinicaltrials.gov, CADENCE, NCT01495091 https://clinicaltrials.gov/ct2/show/NCT01495091?term = 01495091&draw = 2&rank = 1.

High-Sensitivity Cardiac Troponin T Is a Risk Factor for Major Adverse Cardiovascular Events and All-Cause Mortality: A 9.5-Year Follow-Up Study

BACKGROUND

The relationship between high-sensitivity cardiac troponin T (hs-cTnT) and different cardiovascular events has been observed in several large community studies, and the results have been controversial. However, there is currently no cross-sectional or longitudinal follow-up study on hs-cTnT in the Chinese population.

METHODS

We analyzed the association of plasma hs-cTnT levels with major adverse cardiovascular events (MACEs) and all-cause mortality in 1325 subjects from a longitudinal follow-up community-based population in Beijing, China.

RESULTS

In the Cox proportional hazards models analysis, the risk of MACEs increased with the increase of hs-cTnT levels (HR, 1.223, 95% CI, 1.054-1.418, P=0.008). Increased hs-cTnT levels were associated with coronary events (HR, 1.391, 95% CI, 1.106-1.749, P=0.005) in Model 4. Cox proportional risk regression model analysis revealed that increased hs-cTnT levels were associated with an increased risk of mortality (HR, 1.763, 95% CI, 1.224-2.540, P=0.002), even after adjusting hs-CRP and NT-proBNP. The area under the ROC curve for predicting MACEs was 0.559 (95% CI, 0.523-0.595, P=0.001). The areas under the ROC curve for predicting coronary events and mortality were 0.629 (95% CI, 0.580-0.678, P < 0.001) and 0.644 (95% CI, 0.564-0.725, P < 0.001), respectively.

CONCLUSIONS

Our findings in the Chinese cohort support that hs-cTnT is a risk factor for major adverse cardiovascular events and all-cause mortality.

Nourin-Dependent miR-137 and miR-106b: Novel Biomarkers for Early Diagnosis of Myocardial Ischemia in Coronary Artery Disease Patients

Background: Although cardiovascular imaging techniques are widely used to diagnose myocardial ischemia in patients with suspected stable coronary artery disease (CAD), they have limitations related to lack of specificity, sensitivity and “late” diagnosis. Additionally, the absence of a simple laboratory test that can detect myocardial ischemia in CAD patients, has led to many patients being first diagnosed at the time of the development of myocardial infarction. Nourin is an early blood-based biomarker rapidly released within five minutes by “reversible” ischemic myocardium before progressing to necrosis. Recently, we demonstrated that the Nourin-dependent miR-137 (marker of cell damage) and miR-106b-5p (marker of inflammation) can diagnose myocardial ischemia in patients with unstable angina (UA) and also stratify severity of ischemia, with higher expression in acute ST-segment elevation myocardial infarction (STEMI) patients compared to UA patients. Minimal baseline-gene expression levels of Nourin miRNAs were detected in healthy subjects. Objectives: To determine: (1) whether Nourin miRNAs are elevated in chest pain patients with myocardial ischemia suspected of CAD, who also underwent dobutamine stress echocardiography (DSE) or ECG/Treadmill stress test, and (2) whether the elevated levels of serum Nourin miRNAs correlate with results of ECHO/ECG stress test in diagnosing CAD patients. Methods: Serum gene expression levels of miR-137, miR-106b-5p and their corresponding molecular pathway network were measured blindly in 70 enrolled subjects using quantitative real time PCR (qPCR). Blood samples were collected from: (1) patients with chest pain suspected of myocardial ischemia (n = 38) both immediately “pre-stress test” and “post-stress test” 30 min. after test termination; (2) patients with acute STEMI (n = 16) functioned as our positive control; and (3) healthy volunteers (n = 16) who, also, exercised on ECG/Treadmill stress test for Nourin baseline-gene expression levels. Results: (1) strong correlation was observed between Nourin miRNAs serum expression levels and results obtained from ECHO/ECG stress test in diagnosing myocardial ischemia in CAD patients; (2) positive “post-stress test” patients with CAD diagnosis showed upregulation of miR-137 by 572-fold and miR-106b-5p by 122-fold, when compared to negative “post-stress test” patients (p < 0.001); (3) similarly, positive “pre-stress test” CAD patients showed upregulation of miR-137 by 1198-fold and miR-106b-5p by 114-fold, when compared to negative “pre-stress test” patients (p < 0.001); and (4) healthy subjects had minimal baseline-gene expressions of Nourin miRNAs. Conclusions: Nourin-dependent miR-137 and miR-106b-5p are promising novel blood-based biomarkers for early diagnosis of myocardial ischemia in chest pain patients suspected of CAD in outpatient clinics. Early identification of CAD patients, while patients are in the stable state before progressing to infarction, is key to providing crucial diagnostic steps and therapy to limit adverse cardiac events, improve patients’ health outcome and save lives.

High-Sensitivity Cardiac Troponin After Cardiac Stress Test: A Systematic Review and Meta-Analysis

Background The recent introduction of high-sensitivity cardiac troponin (hs-cTn) assays has allowed clinicians to measure hs-cTn before and after cardiac stress testing, but the hs-cTn release pattern and potential utility in identifying inducible myocardial ischemia are unclear. We thus conducted a systematic review and meta-analysis to improve our understanding of hs-cTn release associated with exercise and pharmacological stress testing. Methods and Results Studies published between January 2008 and July 2016 that reported hs-cTn change values (high-sensitivity cardiac troponin T [hs-cTnT] or high-sensitivity cardiac troponin I [hs-cTnI]) in relation to cardiac stress testing were searched and reviewed by 2 independent screeners. Primary outcomes were pooled estimates of absolute and relative hs-cTn changes after cardiac stress test, stratified by the presence of inducible myocardial ischemia. This meta-analysis included 11 studies (n=2432 patients). After exercise stress testing, hs-cTnT increased by 0.5 ng/L or 11% (6 studies, n=406) and hs-cTnI by 2.4 ng/L or 41% (4 studies, n=365) in patients with inducible myocardial ischemia versus hs-cTnT by 1.1 ng/L or 18% (8 studies, n=629; P=0.29) and hs-cTnI by 1.8 ng/L or 72% (4 studies, n=831; P=0.61) in patients who did not develop inducible myocardial ischemia. After pharmacological stress test, hs-cTnT changed by -0.1 ng/L or -0.4% (6 studies, n=251) and hs-cTnI by 2.4 ng/L or 32% (2 studies, n=108) in patients with inducible myocardial ischemia versus hs-cTnT by 0.7 ng/L or 11% (5 studies, n=443, P=0.44) and hs-cTnI by 1.7 ng/L or 38% (2 studies, n=116; P=0.62) in patients who did not develop inducible myocardial ischemia. Conclusions hs-cTn rising patterns after exercise and pharmacological stress testing appear inconsistent and comparably small, and do not appear to be correlated with inducible myocardial ischemia.

Cardiac Biomarkers in Patients with Cancer: Considerations, Clinical Implications, and Future Avenues

PURPOSE OF THE REVIEW

As the number of cancer survivors increases due to early screening and modern (antineoplastic) treatments, cancer treatment associated cardiotoxicity (CTAC) is becoming an increasing health burden that affects survival and quality of life among cancer survivors. Thus, clinicians need to identify adverse events early, in an effort to take suitable measures before the occurrence of permanent or irreversible cardiac dysfunction.

RECENT FINDINGS

Cardiac troponin (cTn) and B-type natriuretic peptide (BNP) have been proven to detect subclinical cardiotoxicity during antineoplastic treatment. As such, these cardio-specific biomarkers could predict which patients are at risk of developing CTAC even before the start of therapy. Nevertheless, there are inconsistent data from published studies, and the recommendations regarding the use of these biomarkers and their validity are mostly based on expert consensus opinion. In this review, we summarize available literature that evaluates biomarkers of CTAC, and we encourage strategies that integrate circulating biomarkers and cardiac imaging in identifying cancer patients that are at high risk.

Stronger correlation with myocardial ischemia of high-sensitivity troponin T than other biomarkers

BACKGROUND

Acute myocardial infarction (AMI) is considered a major cause of death and disability. Myocardial perfusion scintigraphy (MPS) as a non-invasive diagnostic imaging procedure and certain biomarkers associated with myocardial ischemia (ISCH), such as ischemia-modified albumin (IMA), neuropeptide Y (NPY), N-terminal pro b-type natriuretic peptide (NT-proBNP), and high-sensitivity troponin T (hsTnT) could probably aid in the detection of myocardial infarction.

METHODS

Between December 2011 and June 2012, we prospectively analyzed patients who underwent a MPS study with the clinical question of myocardial ISCH. An exercise test was performed along with a MPS. Blood was drawn from the patients before exercise and the within 3 minutes from achieving maximum load and was analyzed for the aforementioned biomarkers.

RESULTS

A total of 71 patients (56 men and 15 women) were enrolled with a mean age of 61 ± 12 years. Twenty-six patients (36.6%) showed reduced uptake on stress MPS images that normalized at rest, a finding consistent with ISCH. Between ISCH and non-ISCH groups, only hsTnT levels showed a significant difference with the highest levels pertaining to the former group both before (0.0075 ng/ml vs 0.0050 ng/ml, P = 0.023) and after stress exercise (0.0085 vs 0.0050, P = 0.015). The most prominent differences were seen in higher stages of the Bruce protocol (stress duration > 9.05 minutes - P < 0.017). None of the IMA, NPY, and NP-pro BNP showed significant differences in time between the two groups.

CONCLUSIONS

Although IMA, NPY, and NT-pro BNP may not detect minor ischemic myocardial insults, serum hsTnT holds a greater ability of detecting not only myocardial infarction but also less severe ischemia. Further studies with larger cohorts of patients are warranted in order to better define the role of hsTnT as a screening tool for myocardial ischemia.

Post-exercise high-sensitivity troponin T levels in patients with suspected unstable angina

Background

Previous studies showed that troponin blood levels may increase after exercise. In this study we assessed whether, among patients admitted with suspected unstable angina, the increase in high-sensitive troponin T (hs-TnT) levels after exercise stress test (EST) might help identify those with obstructive coronary artery disease (CAD) and predict symptom recurrence during short term follow-up.

Methods

Maximal treadmill EST was performed in 69 consecutive patients admitted to the emergency room with a suspicion of unstable angina (acute chest pain but confirmed normal serum levels of cardiac troponins) was measured before and 4 hours after EST. Coronary angiography was performed in 22 patients (32.8%).

Results

hs-TnT increased after EST compared to baseline in the whole population (from 0.84±0.65 to 1.17±0.87 ng/dL, p<0.001). The increase was similar in patients with positive (n = 14) and negative (n = 55) EST (p = 0.72), and was also similar in patients with (n = 12) and without (n = 10) obstructive CAD at angiography (p = 0.91). The achievement of a heart rate at peak EST ≥85% of that predicted for age was the variable mainly associated with the post-EST hs-TnT increase at multivariable linear regression analysis (p = 0.005). The change after EST of hs-TnT did not predict the recurrence of symptoms or readmission for chest pain at 6-month follow-up.

Conclusions

Our data show that hs-TnT increased after EST in patients with suspected unstable angina, which seemed largely independent of most clinical and laboratory variables. Thus, hs-TnT assessed after EST does not seem to be helpful to identify patients with obstructive CAD in this kind of patients.

Cardiac Troponin T Concentrations, Reversible Myocardial Ischemia, and Indices of Left Ventricular Remodeling in Patients with Suspected Stable Angina Pectoris: a DOPPLER-CIP Substudy

BACKGROUND

Cardiac troponin T concentrations measured with high-sensitivity assays (hs-cTnT) provide important prognostic information for patients with stable coronary artery disease (CAD). However, whether hs-cTnT concentrations mainly reflect left ventricular (LV) remodeling or recurrent myocardial ischemia in this population is not known.

METHODS

We measured hs-cTnT concentrations in 619 subjects with suspected stable CAD in a prospectively designed multicenter study. We identified associations with indices of LV remodeling, as assessed by cardiac MRI and echocardiography, and evidence of myocardial ischemia diagnosed by single positron emission computed tomography.

RESULTS

Median hs-cTnT concentration was 7.8 ng/L (interquartile range, 4.8–11.6 ng/L), and 111 patients (18%) had hs-cTnT concentrations above the upper reference limit (&gt;14 ng/L). Patients with hs-cTnT &gt;14 ng/L had increased LV mass (144 ± 40 g vs 116 ± 34 g; P &lt; 0.001) and volume (179 ± 80 mL vs 158 ± 44 mL; P = 0.006), lower LV ejection fraction (LVEF) (59 ± 14 vs 62 ± 11; P = 0.006) and global longitudinal strain (14.1 ± 3.4% vs 16.9 ± 3.2%; P &lt; 0.001), and more reversible perfusion defects (P = 0.001) and reversible wall motion abnormalities (P = 0.008). Age (P = 0.009), estimated glomerular filtration rate (P = 0.01), LV mass (P = 0.003), LVEF (P = 0.03), and evidence of reversible myocardial ischemia (P = 0.004 for perfusion defects and P = 0.02 for LV wall motion) were all associated with increasing hs-cTnT concentrations in multivariate analysis. We found analogous results when using the revised US upper reference limit of 19 ng/L.

CONCLUSIONS

hs-cTnT concentrations reflect both LV mass and reversible myocardial ischemia in patients with suspected stable CAD.

High sensitivity cardiac troponins: Can they help in diagnosing myocardial ischaemia?

BACKGROUND

Cardiac troponin is the most sensitive marker of myocardial injury, but controversy still exists about its role in detecting ischaemia.

METHODS

To investigate the role of troponin as a marker of stress-induced ischaemia, circulating high sensitivity cardiac troponin T (hs-cTnT) was measured and compared with the MB fraction of creatine kinase (CK-MB) in 125 patients undergoing a stress test (53 electrocardiogram/echo exercise, 42 echo dipyridamole and 30 echo dobutamine tests).

RESULTS

Plasma concentrations of hs-cTnT increased after the tests in 90/125 patients, while an increase of CK-MB was seen in 31/125 patients ( p<0.0001). Overall, hs-cTnT significantly increased from 17.5±16.9 ng/l to 25.5±27.9 ng/l ( p<0.0001), without significant changes of CK-MB. Significant increments in hs-cTnT were documented after exercise test (from 15.9±11.9 ng/l to 19.5±13.6 ng/l, p<0.0001) and dobutamine test (from 20.6±20.8 ng/l to 37.8±31.1 ng/l, p=0.0006), in absence of changes in CK-MB according to each stressor. Among the 125 tests, 84 were diagnosed as negative and 41 as positive for myocardial ischaemia. Significant increments in hs-cTnT were detected after both negative (from 18.6±19.2 ng/l to 27.1±32.1 ng/l, p=0.0018) and positive test (from 15.2±10.8 ng/l to 22.3±16.2 ng/l, p=0.0005), without significant changes of CK-MB according to the test result. Despite a positive correlation between stress-induced increase of hs-cTnT and obstructive coronary artery disease, the release of troponin was observed also in a significant proportion of patients without coronary stenoses. Left ventricular hypertrophy markedly enhanced myocardial release of troponin.

CONCLUSIONS

Circulating troponin increases in most patients undergoing a stress test, irrespective of the test result and of coronary artery disease. Plasma release of troponin depends on multiple pathogenetic mechanisms, making the biomarker a not reliable tool in detecting transient ischaemia.

Association Between High-Sensitivity Cardiac Troponin Levels and Myocardial Ischemia During Mental Stress and Conventional Stress

OBJECTIVES

This study sought to investigate whether patients with mental stress-induced myocardial ischemia will have high resting and post-mental stress high-sensitivity cardiac troponin I (hs-cTnI).

BACKGROUND

Hs-cTnI is a marker of myocardial necrosis, and its elevated levels are associated with adverse outcomes. Hs-cTnI levels may increase with exercise in patients with coronary artery disease. Mental stress-induced myocardial ischemia is also linked to adverse outcomes.

METHODS

In this study, 587 patients with stable coronary artery disease underwent technetium Tc 99m sestamibi-single-photon emission tomography myocardial perfusion imaging during mental stress testing using a public speaking task and during conventional (pharmacological/exercise) stress testing as a control condition. Ischemia was defined as new/worsening impairment in myocardial perfusion using a 17-segment model.

RESULTS

The median hs-cTnI resting level was 4.3 (interquartile range [IQR]: 2.9 to 7.3) pg/ml. Overall, 16% and 34.8% of patients developed myocardial ischemia during mental and conventional stress, respectively. Compared with those without ischemia, median resting hs-cTnI levels were higher in patients who developed ischemia either during mental stress (5.9 [IQR: 3.9 to 8.3] pg/ml vs. 4.1 [IQR: 2.7 to 7.0] pg/ml; p < 0.001) or during conventional stress (5.4 [IQR: 3.9 to 9.3] pg/ml vs. 3.9 [IQR: 2.5 to 6.5] pg/ml; p < 0.001). Patients with high hs-cTnI (cutoff of 4.6 pg/ml for men and 3.9 pg/ml for women) had greater odds of developing mental (odds ratio [OR]: 2.4; 95% confidence interval [CI]: 1.5 to 3.9; p < 0.001) and conventional (OR: 2.4; 95% CI: 1.7 to 3.4; p < 0.001) stress-induced ischemia. Although there was a significant increase in 45-min post-treadmill exercise hs-cTnI levels in those who developed ischemia, there was no significant increase after mental or pharmacological stress test.

CONCLUSIONS

In patients with coronary artery disease, myocardial ischemia during either mental stress or conventional stress is associated with higher resting levels of hs-cTnI. This suggests that hs-cTnI elevation is an indicator of chronic ischemic burden experienced during everyday life. Whether elevated hs-cTnI levels are an indicator of adverse prognosis beyond inducible ischemia or whether it is amenable to intervention requires further investigation.

Myocardial Ischemia on Exercise Stress Echocardiography Testing Is Not Associated with Changes in Troponin T Concentrations

BACKGROUND

Some posit that any amount of myocardial ischemia can be detected by high-sensitivity cardiac troponin assays. We hypothesized that patients with myocardial ischemia induced by exercise stress would have significantly higher increases in high-sensitivity cardiac troponin T (hs-cTnT) concentrations than patients without ischemia.

METHODS

We prospectively recruited for a biorepository 317 adult patients who presented to an academic hospital emergency department for evaluation possible ischemic symptoms and who were scheduled for exercise echocardiography. Blood samples were obtained before stress testing and 2-h post-testing. For this study, plasma hs-cTnT (Roche Diagnostics) concentrations were determined in a core laboratory blinded to clinical status. Absolute and relative changes between baseline and 2-h post-stress measurements were compared between patients with and without ischemia induced by stress testing.

RESULTS

The median age was 51 (44.0, 60.0) years, 45.9% were male, and 37.8% were African American. In total, 26 patients (8.1%) had myocardial ischemia induced by exercise. Median baseline, 2-h post-stress, and absolute δ concentrations were, respectively, 6.0, 8.0, and 0.2 ng/L for patients with evidence of ischemia; 3.8, 4.6, and 0.0 ng/L for those without; and 3.9, 4.9, and 0.0 ng/L overall. Baseline and 2-h hs-cTnT concentrations were higher among patients with abnormal stress tests (all P ≤0.05), but absolute and relative changes in hs-cTnT concentrations were not significantly different between individuals with ischemia and individuals without.

CONCLUSIONS

There was no evidence of change in hs-cTnT values in response to exercise stress testing, regardless of the presence of myocardial ischemia.

Troponin T release is associated with silent myocardial ischaemia in black men: The SABPA Study

Background High sensitivity cardiac troponin T (hs-cTnT) is a validated marker of myocardial damage and may reflect the degree of silent myocardial ischaemia (SMI) and ventricular strain. Our aim was to compare hs-cTnT levels in black and white South Africans taking SMI into consideration. We further explored the capability of hs-cTnT to predict the presence of compensatory systolic hypertension in this South African cohort. Methods A bi-ethnic sex cohort ( n = 404) with similar socioeconomic status (198 black participants and 206 white participants, aged 20-65 years) participated in this target population study where 24 h ambulatory blood pressure, electrocardiogram and overnight fasting cardiometabolic variables were measured. Results Hypertension, higher glycated haemoglobin levels and more frequent and longer SMI events were observed more often in the black participants. Multivariate linear regression analysis showed positive associations between SMI events [Adj. R²= 0.19; β 0.35 (0.08-0.62); p < 0.01], SMI event maximum duration [Adj. R²= 0.17, β 0.43 (0.16-0.70), p < 0.01], SMI total duration [Adj. R²= 0.12; β 0.37 (0.10; 0.65), p = 0.05] and hs-cTnT in black males only.] A lower hs-cTnT cut-point ≥4.2 pg/ml for 24 h systolic hypertension was predicted in the black participants compared with ≥5.6 pg/ml in the white participants (area under the curve 0.66-67 (95% CI: 0.57-0.75), p < 0.001) with a respective sensitivity/specificity of 64/68% and 61/71%. Conclusions hs-cTnT may be a potential marker of SMI in the prediction of systolic blood pressure increases, as well as clusters of risk factors for cardiovascular disease. Ethnic- and possibly sex-specific references values for hs-cTnT should be considered for risk stratification.

Evaluation of Serial High Sensitivity Troponin T Levels in Individuals Without Overt Coronary Heart Disease Following Exercise Stress Testing

BACKGROUND

Detectable levels of high sensitivity (cardiac) troponin T (HsTnT), occur in the majority of patients with stable coronary heart disease (CHD), and often in 'healthy' individuals. Extreme physical activity may lead to marked elevations in creatine kinase MB and TnT levels. However, whether HsTnT elevations occur commonly after exercise stress testing (EST), and if so, whether this has clinical significance, needs clarification.

METHODS

To determine whether HsTnT levels become elevated after EST (Bruce protocol) to ≥95% of predicted maximum heart rate in presumed healthy subjects without overt CHD, we assayed HsTnT levels for ∼5h post-EST in 105 subjects (median age 37 years).

RESULTS

Pre-EST HsTnT levels <5 ng/L were present in 31/32 (97%) of females and 52/74 (70%) of males. Post-EST, 13 (12%) subjects developed HsTnT levels >14 ng/L, with troponin elevation occurring at least three hours post-EST. Additionally, a detectable ≥ 50% increase in HsTnT levels (4.9→9ng/L) occurred in 28 (27%) of subjects who during EST achieved ≥ 95% of their predicted target heart rate. The median age of the subjects with HsTnT elevations to > 14ng/L post-EST was higher than those without such elevation (42 and 36 years respectively; p=0.038). At a median follow-up of 13 months no adverse events were recorded.

CONCLUSION

The current study demonstrates that detectable elevations occur in HsTnT post-EST in 'healthy' subjects without overt CHD. Future studies should evaluate the clinical significance of detectable elevations in post-EST HsTnT with long-term follow-up for adverse cardiac events.

Troponin in Cardiovascular Disease Prevention: Updates and Future Direction

Cardiac troponin has been well described as the preferred biomarker for diagnosis of myocardial infarction due to the high sensitivity and specificity for myocardial injury. Numerous other conditions apart from acute coronary syndrome can also lead to small elevations in troponin levels. However, the use of cTn as prognostic biomarker for the primary assessment of cardiovascular risk in asymptomatic patient has only recently been described. And with the development of newer generations of high-sensitivity cardiac troponin assays that can detect 10-fold lower concentrations of troponin, the potential value cTn in the prevention and management of asymptomatic cardiovascular disease has come to the fore. This review provides an overview of the transition of cardiac troponin as a marker of acute myocardial injury to one that detects sub-clinical injury. Evidence continues to show that high-sensitivity troponin is emerging as one of the most powerful prognostic biomarkers for the assessment of cardiovascular risk in the general population.

Plasma Macrophage Migration Inhibitor Factor Is Elevated in Response to Myocardial Ischemia

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a key regulator of inflammatory responses, including in the heart. Plasma MIF is elevated early in the course of acute myocardial infarction. In this study, we hypothesized that plasma MIF may also be increased in acute myocardial ischemia.

METHODS AND RESULTS

Patients undergoing cardiac stress test (stress nuclear myocardial perfusion scan or stress echocardiography) were recruited. Twenty-two patients had a stress test indicative of myocardial ischemia and were compared with 62 patients who had a negative stress test. Plasma MIF was measured by ELISA before and after the stress test. MIF was also measured in patients with peripheral arterial occlusive disease before and after exercise causing claudication. Gene and protein expression of MIF was measured in mouse cardiac and skeletal muscle tissue by real-time polymerase chain reaction and western blot, respectively. Plasma MIF was elevated at 5 and 15 minutes after stress (relative to before stress) in patients with a positive test, compared with those with a negative test. In contrast, high-sensitivity troponin T and C-reactive protein were not altered after stress in either group. MIF was not altered after exercise in PAOD patients, despite the occurrence of claudication, suggesting that plasma MIF is not a marker for skeletal muscle ischemia. This may be explained by a lower gene and protein expression of MIF in skeletal muscle than the heart.

CONCLUSIONS

Our results suggest that plasma MIF is an early marker for acute myocardial ischemia.

Coronary angiography-related myocardial injury as detected by high-sensitivity cardiac troponin T assay

AIMS

We sought to evaluate rates and mechanisms of myocardial injury and type 4a myocardial infarction (MI) after an elective diagnostic coronary angiography (CAG) as detected by high-sensitivity cardiac troponin T (hsTnT) assay.

METHODS AND RESULTS

Cardiac troponin concentrations were measured in consecutive patients before and after undergoing an elective CAG -with or without coronary intervention (PCI)- using an hsTnT assay. The study population consisted of 545 patients: 320 (58.7%) patients received only an elective CAG and another 225 patients (41.3%) received an additional PCI. Significant hsTnT increases occurred in 97 (30.3%) cases within the CAG group and in 152 (67.6%) cases within the PCI group. Rates of normal baseline hsTnT values (<99th percentile upper reference limit) were 75.9% in the CAG group and 71.6% in the PCI group. In cases with normal baseline hsTnT values, peak levels meeting criteria of MI type 4a according to the second or third version of the universal MI definition were observed in five (1.6%) and one (0.3%) cases within the CAG group, as well as in 32 (14.2%) and 22 (9.8%) cases within the PCI group, respectively.

CONCLUSIONS

Use of the hsTnT assay may allow identification of myocardial injury during an uneventful diagnostic coronary angiography in the absence of any coronary or non-coronary interventions.

Serial High-Sensitivity Troponin T in Post-Primary Angioplasty Exercise Test

BACKGROUND

The kinetics of high-sensitivity troponin T (hscTnT) release should be studied in different situations, including functional tests with transient ischemic abnormalities.

OBJECTIVE

To evaluate the release of hscTnT by serial measurements after exercise testing (ET), and to correlate hscTnT elevations with abnormalities suggestive of ischemia.

METHODS

Patients with acute ST-segment elevation myocardial infarction (STEMI) undergoing primary angioplasty were referred for ET 3 months after infarction. Blood samples were collected to measure basal hscTnT immediately before (TnT0h), 2 (TnT2h), 5 (TnT5h), and 8 hours (TnT8h) after ET. The outcomes were peak hscTnT, TnT5h/TnT0h ratio, and the area under the blood concentration-time curve (AUC) for hscTnT levels. Log-transformation was performed on hscTnT values, and comparisons were assessed with the geometric mean ratio, along with their 95% confidence intervals. Statistical significance was assessed by analysis of covariance with no adjustment, and then, adjusted for TnT0h, age and sex, followed by additional variables (metabolic equivalents, maximum heart rate achieved, anterior wall STEMI, and creatinine clearance).

RESULTS

This study included 95 patients. The highest geometric means were observed at 5 hours (TnT5h). After adjustments, peak hscTnT, TnT5h/TnT0h and AUC were 59% (p = 0.002), 59% (p = 0.003) and 45% (p = 0.003) higher, respectively, in patients with an abnormal ET as compared to those with normal tests.

CONCLUSION

Higher elevations of hscTnT may occur after an abnormal ET as compared to a normal ET in patients with STEMI.

Clinical benefit of high-sensitivity cardiac troponin I in the detection of exercise-induced myocardial ischemia

BACKGROUND

A pilot study using a novel high-sensitivity cardiac troponin I (hs-cTnI) assay suggested that cTnI might be released into blood during exercise-induced myocardial ischemia. We investigated the potential clinical value of this signal.

METHODS

We included 819 patients with suspected exercise-induced myocardial ischemia referred for rest/bicycle myocardial perfusion single-photon emission computed tomography. The treating cardiologist used all available clinical information to quantify clinical judgment regarding the presence of myocardial ischemia using a visual analog scale twice: prior and after stress testing. High-sensitivity cTnI measurements were obtained before, immediately after peak stress, and 2 hours after stress testing in a blinded manner. Myocardial ischemia was adjudicated using perfusion single-photon emission computed tomography and coronary angiography findings.

RESULTS

Exercise-induced myocardial ischemia was detected in 278 (34%) patients. High-sensitivity cTnI levels were significantly higher at all time points in patients with myocardial ischemia as compared with those without (P < .001 for all). Combining clinical judgment prior exercise testing with baseline hs-cTnI levels increased diagnostic accuracy as quantified by the area under the receiver operating characteristics curve (AUC) from 0.672 to 0.757 (P < .001). Combining clinical judgment after exercise testing (AUC 0.704) with baseline or poststress hs-cTnI levels also increased the diagnostic accuracy (AUC 0.761-0.771, P < .001 for all). In contrast, exercise-induced changes in hs-cTnI during exercise did not seem useful, as they were small and similar in patients with or without myocardial ischemia.

CONCLUSIONS

High-sensitivity cTnI concentrations at rest and after exercise, but not its exercise-induced changes, provide substantial incremental value to clinical judgment including exercise electrocardiography regarding the presence of myocardial ischemia.

Direct comparison of cardiac troponin I and cardiac troponin T in the detection of exercise-induced myocardial ischemia

BACKGROUND

It is unknown, whether cardiac troponin (cTn) I or cTnT is the preferred biomarker in the detection of exercise-induced myocardial ischemia.

METHODS

We investigated patients with suspected myocardial ischemia referred for exercise or pharmacological rest/stress myocardial perfusion single-photon emission computed tomography (SPECT) to directly compare the diagnostic accuracy of high-sensitivity cTnI (hs-cTnI) and hs-cTnT. Diagnostic performance was analyzed separately according to stress modality. Hs-cTnI and hs-cTnT were measured before, immediately after, as well as 2h and 4h after maximal exercise in a blinded fashion. Further, all clinical information available to the treating cardiologist was used to quantify the clinical judgment regarding the presence of myocardial ischemia using a visual analog scale twice: once prior and once after stress-testing. The presence of stress-induced myocardial ischemia was adjudicated using SPECT combined with coronary angiography findings.

RESULT

A total of 403 consecutive patients were enrolled in our study, of which 229 underwent exercise stress and 174 patients pharmacological stress. Exercise-stress-induced myocardial ischemia was detected in 90 patients (39.3% of 229). Levels of hs-cTnI and hs-cTnT were both significantly higher at all time-points examined in patients with exercise-induced myocardial ischemia as compared to patients without myocardial ischemia (all p<0.001). Correlation of hs-cTnI and hs-cTnT was high in direct comparison of time-points (Spearman's rho all ≥0.7). The AUCs for baseline/peak/2h/4h for hs-cTnI and hs-cTnT were 0.71/0.71/0.72/0.69 vs. 0.74/0.73/0.71/0.72, respectively (all p=ns for hs-cTnI versus hs-cTnT). In patients undergoing pharmacological stress, the AUCs for baseline/peak/2h/4h for hs-cTnI and hs-cTnT were 0.66/0.66/0.68/0.67 and 0.61/0.62/0.64/0.59, respectively (all p=ns for hs-cTnI versus hs-cTnT). Also the combinations including clinical judgment or changes during serial sampling were similar for hs-cTnI and hs-cTnT (all p=ns).

CONCLUSIONS

Hs-cTnI and hs-cTnT provide comparable diagnostic information regarding exercise-induced myocardial ischemia. Overall, their diagnostic accuracy seems moderate.

UNIQUE IDENTIFIER

NCT01838148.

HAX-1 regulates cyclophilin-D levels and mitochondria permeability transition pore in the heart

The major underpinning of massive cell death associated with myocardial infarction involves opening of the mitochondrial permeability transition pore (mPTP), resulting in disruption of mitochondria membrane integrity and programmed necrosis. Studies in human lymphocytes suggested that the hematopoietic-substrate-1 associated protein X-1 (HAX-1) is linked to regulation of mitochondrial membrane function, but its role in controlling mPTP activity remains obscure. Herein we used models with altered HAX-1 expression levels in the heart and uncovered an unexpected role of HAX-1 in regulation of mPTP and cardiomyocyte survival. Cardiac-specific HAX-1 overexpression was associated with resistance against loss of mitochondrial membrane potential, induced by oxidative stress, whereas HAX-1 heterozygous deficiency exacerbated vulnerability. The protective effects of HAX-1 were attributed to specific down-regulation of cyclophilin-D levels leading to reduction in mPTP activation. Accordingly, cyclophilin-D and mPTP were increased in heterozygous hearts, but genetic ablation of cyclophilin-D in these hearts significantly alleviated their susceptibility to ischemia/reperfusion injury. Mechanistically, alterations in cyclophilin-D levels by HAX-1 were contributed by the ubiquitin-proteosomal degradation pathway. HAX-1 overexpression enhanced cyclophilin-D ubiquitination, whereas proteosomal inhibition restored cyclophilin-D levels. The regulatory effects of HAX-1 were mediated through interference of cyclophilin-D binding to heat shock protein-90 (Hsp90) in mitochondria, rendering it susceptible to degradation. Accordingly, enhanced Hsp90 expression in HAX-1 overexpressing cardiomyocytes increased cyclophilin-D levels, as well as mPTP activation upon oxidative stress. Taken together, our findings reveal the role of HAX-1 in regulating cyclophilin-D levels via an Hsp90-dependent mechanism, resulting in protection against activation of mPTP and subsequent cell death responses.

High-sensitivity cardiac troponin T in stable patients undergoing pharmacological stress testing

BACKGROUND

Acute changes in high-sensitivity troponin T (hs-TnT) are induced by myocardial ischemia during exercise stress testing, but there are no reports of pharmacological stress testing.

HYPOTHESIS

The pattern of troponin release by myocardial ischemia-induced pharmacological stress testing differs according to the ischemic burden in stable patients.

METHODS

In total, 250 patients with suspected coronary artery disease underwent pharmacological stress magnetic resonance imaging (MRI). The amount and degree of myocardial ischemia on MRI and ischemic outcomes at 6 months were determined. hs-TnT levels were measured at baseline and 1 and 3 hours after testing. The 6-month clinical outcome was prespecified.

RESULTS

Fifty-one patients had moderate to severe myocardial ischemia (group A), and 199 patients had no or mild myocardial ischemia (group B). hs-TnT levels were significantly higher in group A than B at baseline (11 vs 8 pg/mL, P = 0.016) and at 1 hour (12 vs 8 pg/mL, P = 0.009) and 3 hours after testing (12 vs 9 pg/mL, P = 0.012). Baseline hs-TnT levels of ≥14 pg/mL showed a 43% sensitivity and 77% specificity in predicting moderate to severe ischemia by MRI (P = 0.03; area under the curve: 0.608, P = 0.017). Patients administered dobutamine had a higher acute change in hs-TnT levels 3 hours after testing than did those administered adenosine (21 vs 0 pg/mL, P < 0.001). There was a trend toward a higher incidence of myocardial infarction in patients with baseline hs-TnT levels of ≥14 pg/mL.

CONCLUSIONS

hs-TnT levels are significantly higher in patients with moderate to severe than no or mild myocardial ischemia.

Troponin T and N-terminal pro B-Type natriuretic peptide and presence of coronary artery disease

BACKGROUND

We tested the effects of exercise intensity, sampling intervals, degree of coronary artery stenosis, and demographic factors on circulating N-terminal pro B-Type natriuretic peptide (NT-pro-BNP) and cardiac Troponin T (cTnT) in subjects suspected of coronary artery disease (CAD).

MATERIALS AND METHODS

A total of 242 subjects referred for diagnostic evaluation of possible CAD had blood samples obtained before, 5 min after, and again 20 h after a symptom-limited exercise test.

RESULTS

Totally 40 subjects had CAD with ≥ 50% stenosis, 115 subjects had no stenosis and 87 subjects served as controls. In univariate analysis CAD-subjects had higher median baseline NT-pro-BNP-levels (85.3 ng/L) compared with non-CAD-subjects (41.3 ng/L) and controls (40.1 ng/L), both p < 0.001, but the association disappeared in multivariate analysis adjusted for age and gender. NT-pro-BNP increased similarly after exercise in CAD-subjects, non-CAD-subjects, and controls (median increase 8.14 ng/L) and the increase was positively associated with baseline NT-pro-BNP but not presence of CAD. Median baseline cTnT was 6.25 ng/L in CAD-subjects and 3.00 ng/L in non-CAD-subjects as well as controls, both p < 0.0001. Median ΔcTnT (baseline to 20 h after exercise) was higher in CAD-subjects than non-CAD-subjects and controls (0.62 ng/L vs. 0.0 ng/L, p < 0.001). A linear relationship between ΔcTnT and 'percent of predicted maximal heart rate achieved' was found in subjects with ≥ 70% stenosis (n = 24, r = 0.4067 p = 0.046).

CONCLUSIONS

Baseline cTnT and ΔcTnT were found to be independently associated with CAD and also with exercise intensity in stable chest pain subjects. These properties were not identified for NT-pro-BNP.

Improvement of risk assessment in systemic light-chain amyloidosis using human placental growth factor

BACKGROUND

Vascular amyloid deposition is common in light-chain amyloidosis resulting in endothelial dysfunction. Human placental growth factor (PlGF), a member of the vascular endothelial growth factor family was found to be altered in diverse pathological conditions, e.g. endothelial dysfunction. This study evaluated the clinical role of PlGF in light-chain amyloidosis.

METHODS

PlGF (cobas-PlGF, Roche Diagnostics, Mannheim, Germany) was analyzed in 125 consecutive patients with AL and correlated with diverse clinical parameters including mortality.

RESULTS

Kidney (n = 76) and heart (n = 57) were predominantly affected by amyloid deposition. Median PlGF was 26.3 (21.1-42.1) ng/L, NT-proBNP 3649 (1124-8581) pg/mL, and hs-TnT 42 (21-107) ng/L. PlGF increased with number of organs involved and with deterioration of renal function. A significant correlation of PlGF with hs-TnT (ρ = 0.306; p = 0.0007) and NT-proBNP (ρ = 0.315; p = 0.0006) was observed, but no correlation was observed with clinical, echocardiography, and electrocardiography parameters of cardiac involvement. In this cohort 1-year all-cause mortality was 19.2 %. The best cutoff discriminating survivors and non-survivors was 28.44 ng/L (sensitivity 66.7 %; specificity 78.1 %). A three-step risk model including hs-TnT and NT-proBNP revealed a better discrimination if patients at intermediary risk were additionally stratified by PlGF. Net reclassification index was 37.2 % (p = 0.002). Multivariate analysis revealed PlGF, difference of involved and uninvolved light chain, number of organs involved and risk class according to troponin T and NT-proBNP as independent predictors of mortality.

CONCLUSION

Plasma PlGF values in AL are invariably associated with the number of involved organs, but not with clinical, echocardiography, and electrocardiography parameters of cardiac involvement. PlGF provide useful information for risk stratification of patients at intermediary risk according to hs-TnT and NT-proBNP.

Troponins in heart failure

The signs and symptoms of heart failure are frequently unspecific and correlate poorly with objective indices of cardiac function. Objective assessment of cardiac function by echocardiography or other imaging modalities also correlate poorly with symptomatic status and functional capacity. Accordingly, there is a need for circulating biomarkers that can provide incremental diagnostic and prognostic information to the existing armamentarium of tests. The introduction of more sensitive assays that allow determination of very low circulating concentrations of the myofibrillar proteins cardiac troponin I and T has not only resulted in improved diagnostic accuracy in the setting of acute coronary syndromes. The high sensitivity assays have also shown that cardiac troponins are frequently found chronically circulating in a variety of acute and chronic, cardiac and non-cardiac disease conditions, including acute heart failure and chronic symptomatic and asymptomatic left ventricular dysfunction. Cardiac troponin I and T provide may provide clinically useful prognostic information both concerning the future risk of developing heart failure in asymptomatic subjects and the risk of fatal events and hospital admissions in those with already established heart failure This review summarizes current literature on the clinical performance and utility of cardiac troponin measurements as diagnostic and prognostic tools in patients with symptomatic heart failure, as well as in those with asymptomatic left ventricular dysfunction, and clinical phenotypes at high risk for developing heart failure, including stable coronary artery disease, left ventricular hypertrophy, and aortic stenosis.

B-type natriuretic peptide and clinical judgment in the detection of exercise-induced myocardial ischemia

BACKGROUND

Myocardial ischemia has been shown to be associated with increased levels of B-type natriuretic peptide (BNP). However, it remains unclear whether and how BNP levels could be used clinically in patients with suspected exercise-induced myocardial ischemia.

METHODS

We enrolled 274 consecutive patients with suspected exercise-induced myocardial ischemia referred for evaluation by rest/bicycle myocardial perfusion single-photon emission computed tomography (SPECT). All clinical information available to the treating cardiologist was used to quantify the clinical judgment regarding the presence of myocardial ischemia using a visual analogue scale twice: once before and once after bicycle exercise stress testing. BNP measurements were obtained before, immediately after, and 2 hours after stress testing in a blinded manner. The presence of myocardial ischemia was adjudicated on the basis of perfusion SPECT combined with coronary angiography findings.

RESULTS

Exercise-induced myocardial ischemia was adjudicated to be present in 103 patients (38%). BNP levels were significantly higher at all time points in patients with myocardial ischemia compared with those without (P < .01 for all). The accuracy of BNP levels as quantified by the area under the receiver operating characteristic curve (AUC) was similar among the time points evaluated (AUC, 0.677-0.697). Combining clinical judgment before exercise testing with BNP levels at rest increased diagnostic accuracy from AUC 0.708 to 0.754 (P = .018). When combining clinical judgment after exercise testing with BNP levels, AUC increased from 0.741 to 0.771 (P = .055).

CONCLUSIONS

Combining clinical judgment with BNP levels increased the diagnostic accuracy regarding the presence of myocardial ischemia.

Obstructive sleep apnea: no independent association to troponins

BACKGROUND

Cardiac troponins (cTn) are to date the most sensitive and specific biochemical markers of myocardial injury. Abnormal breathing patterns in patients with obstructive sleep apnea (OSA) may cause myocardial cell stress detectable by novel cTn assays. The objectives of this study were to investigate whether a new single-molecule cTnI (S-cTnI) assay and a commercially available high-sensitivity cTnT (hs-cTnT) assay would detect myocyte injury in individuals evaluated for possible OSA, and to explore their relation to variables of disordered breathing during sleep.

METHODS

Consecutive individuals referred to Lovisenberg Diakonale Hospital's sleep laboratory between 1 October 2009 and 1 March 2010 were included. We measured cTn in specimens collected the morning after sleep and studied these in relation to variables recorded during polygraphy or polysomnography.

RESULTS

All 222 (100 %) individuals had measurable cTn levels using either assay. Stratified into categories according to the apnea-hypopnea index (AHI), patients with OSA (AHI ≥5) had a different distribution of S-cTnI (P = 0.036) and hs-cTnT (P = 0.002) compared to those without (AHI <5). The median (quartiles 1-3) were 3.0 (1.9-6.0) versus 2.3 (1.6-3.8) ng/l for S-cTnI, and 7.0 (5.5-8.7) versus 6.2 (4.9-7.2) ng/l for hs-cTnT. However, in multiple median regression analyses adjusted for conventional predictors, neither S-cTnI (P = 0.57) nor hs-cTnT (P = 0.80) were significantly associated with AHI.

CONCLUSIONS

This study reveals no association independent of conventional predictors between OSA and myocardial cell injury measured by S-cTnI and hs-cTnT assays. Our findings support a search for novel biomarkers for prognostication of OSA.

Serial measurements of high-sensitivity cardiac troponin T after exercise stress test in stable coronary artery disease

OBJECTIVE

The aim was to assess serial measurements of high-sensitivity cardiac troponin T (hs-cTNT) post-exercise in patients with stable coronary artery disease (CAD).

METHODS

Twelve patients with positive coronary angiograms (CAD positives) and 12 controls performed an exercise stress test.

RESULTS

CAD positive had higher baseline and peak concentrations of hs-cTNT than controls. Significant increases in hs-cTNT were seen in both groups after exercise. In two-third of patients the peak in hs-cTNT was above the 99th percentile.

CONCLUSION

hs-cTNT is higher in patients with stable coronary disease than in controls and exceeds the diagnostic cut-off value for myocardial infarction in a majority of patients with CAD after exercise.

Basal and ischemia-induced transcardiac troponin release into the coronary circulation in patients with suspected coronary artery disease

Background

Cardiac troponin is a specific biomarker for cardiomyocyte necrosis in acute coronary syndromes. Troponin release from the coronary circulation remains to be determined because of the lower sensitivity of the conventional assay. We sought to determine basal and angina-induced troponin release using a highly sensitive troponin assay.

Methods and Results

The cardiac troponin T levels in serum sampled from the peripheral vein (PV), the aortic root (AO), and the coronary sinus (CS) were measured in 105 consecutive stable patients with coronary risk factor(s) and suspected coronary artery disease (CAD) and in 33 patients without CAD who underwent an acetylcholine provocation test. At baseline, there was a significant increase in the troponin levels from AO [9.0 (6.4, 13.1) pg/mL for median (25^th, 75^th percentiles)] to CS [10.3 (7.3, 15.5) pg/mL, p<0.001] in 96 (91.4%) patients and the difference was 1.1 (0.4, 2.1) pg/mL, which reflected basal transcardiac troponin release (TTR). TTR was positively correlated with PV levels (r = 0.22, p = 0.03). Male sex, left ventricular hypertrophy determined by echocardiography, T-wave inversion, and CAD correlated with elevated TTR defined as above: median, 1.1 pg/mL. A significant increase in TTR was noted in 17 patients with coronary spasms [0.6 (0.2, 1.2) pg/mL, p<0.01] but not in 16 patients without spasms [0.0 (−0.5, 0.9) pg/mL, p = 0.73] after the acetylcholine provocation.

Conclusion

Basal TTR in the coronary circulation was observed in most of the patients with suspected CAD and risk factor(s). This sensitive assay detected myocardial ischemia-induced increases in TTR caused by coronary spasms.

Circulating miRNAs: novel biomarkers of acute coronary syndrome?

Acute coronary syndrome refers to any group of clinical symptoms compatible with acute myocardial infarction (AMI). AMI is a major cause of death and disability worldwide with the greatest risk of death within the first hours of AMI onset. Therefore, delays in ‘ruling in’ AMI may increase morbidity and mortality due to the time lag in initiating therapy. Likewise, since the majority of patients presenting with acute chest pain do not have AMI, the rapid ‘ruling out’ of AMI in those patients would increase emergency department triage efficiency, decrease medical costs, and reduce morbidity and mortality. Thus, the identification of novel biomarkers that improve current strategies and/or accurately identify subjects who are at risk of developing acute and chronic manifestations of cardiovascular disease are desperately needed. This article discusses the potential of peripheral blood microRNAs as clinical biomarkers for the diagnosis and prognosis of cardiovascular diseases such as AMI.

Single resting hsTnT level predicts abnormal myocardial stress test in acute chest pain patients with normal initial standard troponin

OBJECTIVES

The goal of this study was to determine the ability of a single, resting high-sensitivity troponin T (hsTnT) measurement to predict abnormal myocardial perfusion imaging (MPI) in patients presenting with acute chest pain to the emergency department (ED).

BACKGROUND

HsTnT assays precisely detect very low levels of troponin T, which may be a surrogate for the presence and extent of myocardial ischemia.

METHODS

We included all patients from the ROMICAT I (Rule Out Myocardial Infarction Using Computer Assisted Tomography) trial, an observational cohort study, who underwent both single-photon emission computed tomography (SPECT)-MPI stress testing and 64-slice computed tomography angiography (CTA) and in whom hsTnT measurements were available. We assessed the discriminatory value of hsTnT for abnormal SPECT-MPI and the association of reversible myocardial ischemia by SPECT-MPI and the extent of coronary atherosclerosis by CTA to hsTnT levels.

RESULTS

Of the 138 patients (mean age 54 ± 11 years, 46% male), 19 (13.7%) had abnormal SPECT-MPI. Median hsTnT levels were significantly different between patients with normal and abnormal SPECT-MPI (9.41 pg/ml [interquartile range (IQR): 5.73 to 19.20 pg/ml] vs. 4.89 pg/ml [IQR: 2.34 to 7.68 pg/ml], p = 0.001). Sensitivity of 80% and 90% to detect abnormal SPECT-MPI was reached at hsTnT levels as low as 5.73 and 4.26 pg/ml, respectively. Corresponding specificity was 62% and 46%, and negative predictive value was 96% and 96%, respectively. HsTnT levels had good discriminatory ability for prediction of abnormal SPECT-MPI (area under the curve: 0.739, 95% confidence interval: 0.609 to 0.868). Both reversible myocardial ischemia and the extent of coronary atherosclerosis (combined model r(2) = 0.19 with partial of r(2) = 0.12 and r(2) = 0.05, respectively) independently and incrementally predicted the measured hsTnT levels.

CONCLUSIONS

In patients with acute chest pain, myocardial perfusion abnormalities and coronary artery disease are predicted by resting hsTnT levels. Prospective evaluations are warranted to confirm whether resting hsTnT could serve as a powerful triage tool in chest pain patients in the ED before diagnostic testing and improve the effectiveness of patient management.

Troponin I measured by a high-sensitivity assay in patients with suspected reversible myocardial ischemia: data from the Akershus Cardiac Examination (ACE) 1 study

BACKGROUND

Whether cardiac troponin concentrations are increased by reversible myocardial ischemia is controversial. Differences in the structure of cardiac troponin I (cTnI) and cTnT may have implications for diagnostic utility.

METHODS

cTnI was measured with a prototype high-sensitivity (hs) assay in 198 patients referred for myocardial perfusion imaging (MPI) before exercise stress testing, immediately after, and 1.5 and 4.5 h later. We categorized patients according to MPI results and compared hs-cTnI concentrations with hs-cTnT concentrations.

RESULTS

Baseline hs-cTnI was higher in patients with reversible myocardial ischemia (n = 19) vs the other patients (n = 179): median 4.4 (quartiles 1-3: 2.3-7.1) vs 2.5 (1.4-4.3) ng/L, P = 0.003. Baseline hs-cTnI and hs-cTnT concentrations were correlated (r = 0.46, P < 0.001) and the areas under the ROC curve for hs-cTnI and hs-cTnT in diagnosing reversible ischemia were similar: 0.71 vs 0.69, P = 0.77. Whereas hs-cTnI increased immediately after exercise (P < 0.001 vs baseline measurements) in patients without ischemia, it increased after 4.5 h in patients with reversible ischemia (P = 0.01). The increment in hs-cTnI concentrations was comparable between groups; thus, measuring hs-cTnI after exercise stress testing did not improve diagnostic accuracy over baseline measurements, and hs-cTnI concentrations were not found to be associated with reversible myocardial ischemia in multivariate analysis. By linear regression analysis, age, male sex, history of hypertension, angiotensin-converting enzyme inhibitor use, and lower left ventricular ejection fraction were associated with higher baseline hs-cTnI concentrations.

CONCLUSIONS

In patients referred to MPI, hs-cTnI concentrations were not closely associated with reversible myocardial ischemia, but rather were influenced by variables associated with structural alterations of the myocardium.

Cardiac Troponin T Measured by a High-Sensitivity Assay Predicts Recurrent Cardiovascular Events in Stable Coronary Heart Disease Patients with 8-Year Follow-up

BACKGROUND

The clinical relevance of slightly increased circulating troponin concentrations in patients with stable coronary heart disease (CHD) several weeks after an acute event or CABG has not been fully evaluated.

METHODS

Baseline plasma concentrations of troponin T were measured with a high-sensitivity assay (hs-cTnT) (Roche Elecsys) in a cohort of 1050 CHD patients from 30 to 70 years of age. The prognostic value of hs-cTnT on a combined cardiovascular disease (CVD) end point after adjustment for covariates was determined with Cox proportional hazards modeling.

RESULTS

The median hs-cTnT concentration was 10.9 ng/L (interquartile range, 5.1–18.9 ng/L). Increased hs-cTnT concentrations were associated with an older age, history of hypertension and diabetes, more advanced coronary artery disease, and other CHD risk factors. Furthermore, hs-cTnT concentration was strongly correlated with N-terminal pro–B-type natriuretic peptide (NT-proBNP) and cystatin C (ρ = 0.61, and ρ = 0.32, respectively; both P values &lt;0.0001). During a median follow-up of 8.1 years, 150 patients (14.3%) experienced a secondary CVD event. In a multivariate model, hs-cTnT was associated with a hazard ratio (HR) for secondary events of 2.83 (95% CI, 1.68–4.79) when the extreme quartiles were compared. Further adjustment for cystatin C, NT-proBNP, and C-reactive protein attenuated this association only slightly (HR, 2.27; 95% CI, 1.31–3.95); P for trend &lt; 0.002). ROC curve analysis of a clinical model that added hs-cTnT to a baseline model showed nonsignificant improvement in the area under the curve (0.69 vs 0.67), whereas the net reclassification improvement was 17.2% (P = 0.029).

CONCLUSIONS

Slightly increased hs-cTnT concentrations in stable CHD patients are associated with several cardiovascular disorders and predict long-term CVD events.

Cardiac troponin T levels and exercise stress testing in patients with suspected coronary artery disease: the Akershus Cardiac Examination (ACE) 1 study

Whether reversible ischaemia in patients referred for exercise stress testing and MPI (myocardial perfusion imaging) is associated with changes in circulating cTn (cardiac troponin) levels is controversial. We measured cTnT with a sensitive assay before, immediately after peak exercise and 1.5 and 4.5 h after exercise stress testing in 198 patients referred for MPI. In total, 19 patients were classified as having reversible myocardial ischaemia. cTnT levels were significantly higher in patients with reversible myocardial ischaemia on MPI at baseline, at peak exercise and after 1.5 h, but not at 4.5 h post-exercise. In patients with reversible ischaemia on MPI, cTnT levels did not change significantly after exercise stress testing [11.1 (5.2–14.9) ng/l at baseline compared with 10.5 (7.2–16.3) ng/l at 4.5 h post-exercise, P=0.27; values are medians (interquartile range)]. Conversely, cTnT levels increased significantly during testing in patients without reversible myocardial ischaemia [5.4 (3.0–9.0) ng/l at baseline compared with 7.5 (4.6–12.4) ng/l, P<0.001]. In conclusion, baseline cTnT levels are higher in patients with MPI evidence of reversible myocardial ischaemia than those without reversible ischaemia. However, although cTnT levels increase during exercise stress testing in patients without evidence of reversible ischaemia, this response appears to be blunted in patients with evidence of reversible ischaemia. Mechanisms other than reversible myocardial ischaemia may play a role for acute exercise-induced increases in circulating cTnT levels.

Biomarkers in acute myocardial injury

Acute coronary syndrome (ACS) is a significant cause of morbidity and mortality worldwide. The proper diagnosis of ACS requires reliable and accurate biomarker assays to detect evidence of myocardial necrosis. Currently, troponin is the gold standard biomarker for myocardial injury and is used commonly in conjunction with creatine kinase-MB (CK-MB) and myoglobin to enable a more rapid diagnosis of ACS. A new generation of highly sensitive troponin assays with improved accuracy in the early detection of ACS is now available, but the correct interpretation of assay results will require a careful consideration of assay characteristics and the clinical setting prior to incorporation into routine practice. B-type natriuretic peptides, copeptin, ischemia-modified albumin, heart-type fatty-acid-binding protein, myeloperoxidase, C-reactive protein, choline, placental growth factor, and growth-differentiation factor-15 make up a promising group of other biomarkers that have shown the ability to improve prognosis and diagnosis of ACS compared with traditional markers.

Copeptin Does Not Add Diagnostic Information to High-Sensitivity Troponin T in Low- to Intermediate-Risk Patients with Acute Chest Pain: Results from the Rule Out Myocardial Infarction by Computed Tomography (ROMICAT) Study

PURPOSE

Copeptin, a stable peptide derived from the AVP precursor, has been linked to presence and severity of myocardial ischemia. We sought to evaluate the predictive value of copeptin and its incremental value beyond that of high-sensitivity cardiac troponin T (hs-cTnT) in patients with acute chest pain and low to intermediate risk for acute coronary syndrome (ACS).

METHODS

We recruited patients who presented with acute chest pain to the emergency department and had a negative initial conventional troponin T test (&lt;0.03 μg/L). In all patients, hs-cTnT and copeptin measurements were taken. Each patient also underwent cardiac computed tomography (CT) and coronary angiography.

RESULTS

Baseline copeptin concentrations, in contrast to hs-cTnT, were not significantly higher in patients with ACS than in those without (P = 0.24). hs-cTnT showed an earlier rise in patients with ACS than copeptin, when analyses were stratified by time. A copeptin concentration ≥7.38 pmol/L had a negative predictive value (NPV) of 94% and a sensitivity of 51%, whereas hs-cTnT (≥13.0 pg/mL) had a NPV of 96% and a sensitivity of 63%. The combination of copeptin and hs-cTnT resulted in a lower diagnostic accuracy than hs-cTnT alone. Finally, on cardiac CT, copeptin concentrations were not associated with coronary artery morphology, although they were related to the presence of left ventricular dysfunction (P = 0.02).

CONCLUSIONS

Among patients with acute chest pain and low to intermediate risk for ACS, copeptin concentrations are not independently predictive of ACS and do not add diagnostic value beyond that of hs-cTnT measurements.

Biochemical markers in acute coronary syndrome

Owing to their higher risk for cardiac death or ischemic complications, patients with acute coronary syndrome (ACS) must be identified from other causes of chest pain. Patients with acute coronary syndrome are divided into categories based on their electrocardiogram; those with new ST-segment elevation and those who present with ST-segment depression. The subgroups of patients with ST-segment elevation are candidates for immediate reperfusion, while fibrinolysis appears harmful for those with non-ST elevation myocardial infarction. There is increasing evidence to encourage appropriate risk stratification before deciding on a management strategy (invasive or conservative) for each patient. The TIMI, GRACE or PURSUIT risk models are recommended as useful for decisions regarding therapeutic options. Cardiac biomarkers are useful additions to these clinical tools to correctly risk stratify ACS patients. Cardiac troponin is the biomarker of choice to detect myocardial necrosis and is central to the universal definition of myocardial infarction. The introduction of troponin assays with a lower limit of detection will allow for earlier diagnosis of patients who present with chest pain. Analytical and clinical validations of these new assays are currently in progress. The question is whether the lower detection limit of the troponin assays will be able to indicate myocardial ischemia in the absence of myocardial necrosis. Previous to the development of ultrasensitive cardiac troponin assays free fatty acids unbound to albumin and ischemia modified albumin were proposed as biochemical markers of ischemia. Advances in our knowledge of the pathogenesis of acute coronary thrombosis have stimulated the development of new biomarkers. Markers of left ventricular performance (N-terminal pro-brain natriuretic peptide) and inflammation (e.g. C-reactive protein) are generally recognized as risk indicators. Studies suggest that using a number of biomarkers clinicians can risk stratify patients over a broad range of short and long term cardiac events. Nevertheless, it is still under debate as to which biomarker combination is best preferred for risk prediction. This review will focus on recent practice guidelines for the management of patients with ACS as well as current advances in cardiac biomarkers, their integration into clinical care and their diagnostic, prognostic and therapeutic utility.