Impact of time from symptom onset on the diagnostic performance of high-sensitivity cardiac troponin for type 1 myocardial infarction

Background

High-sensitivity cardiac troponin has enabled the rapid rule-out and rule-in of myocardial infarction at presentation. However, increases in cardiac troponin may not be detectable early after symptom onset, and uncertainty remains as to how time of symptom onset influences diagnostic performance.

Purpose

To evaluate the impact of time from symptom onset on the diagnostic performance of high-sensitivity cardiac troponin for type 1 myocardial infarction.

Methods

In a secondary analysis of a prospective multicentre randomised controlled trial of consecutive patients with suspected acute coronary syndrome, we evaluated the diagnostic performance of high-sensitivity cardiac troponin I measurements at presentation stratified by time of symptom onset to blood sampling. Diagnostic performance was evaluated in four groups (≤3 hours, 4–6 hours, 7–12 hours and >12 hours from symptom onset) for recommended thresholds to rule-out (sex-specific 99th centile and optimised threshold [64 ng/L]) type 1 myocardial infarction.

Results

This analysis included 41,104 patients (median 60 [interquartile range 49–74] years, 46% female) of which 12,595 (31%), 10,298 (25%), 7,171 (17%) and 11,040 (27%) presented ≤3 hours, 4–6 hours, 7–12 hours and >12 hours, respectively. Type 1 myocardial infarction was the adjudicated diagnosis in 3,692 (9%) patients. For the rule-out of type 1 myocardial infarction, sensitivity was highest in those tested 7–12 hours from symptom onset and lowest in those tested ≤3 hours. In early presenters, a threshold of <2 ng/L had greater sensitivity and negative predictive value (99.4% [95% CI 98.9 to 99.7%] and 99.7% [95% CI 99.5 to 99.9%]) compared to <5 ng/L (96.7% [95% CI 95.7 to 97.6%] and 99.3% [95% CI 99.1 to 99.5%], respectively). In those tested >3 hrs from symptom onset, the sensitivity and negative predictive value for both thresholds were similar, but a threshold of <5 ng/L correctly ruled out more patients (60% [17,056/28,506] versus 29% [8,316/28,506]). For the rule-in of myocardial infarction, the sensitivity of the 99th centile and 64 ng/L was lowest in patients tested within 3 hours (71.7% [95% CI 69.3 to 74.1%] and 46.5% [95% CI 44.1 to 49.2%], respectively), and increased in those tested later from symptom onset. The specificity and positive predictive value were highest when testing was performed 7–12 hours from symptom onset for the sex-specific 99th centile (92.4% [95% CI 91.8 to 93.0%] and 51.3% [95% CI 48.2–54.5%]) and 64 ng/L (96.2% [95% CI 95.7 to 96.7%] and 61.2% [95% CI 57.3 to 65.2%]).

Conclusions

The diagnostic performance of cardiac troponin for myocardial infarction is strongly influenced by the time from symptom onset to testing. In early presenters the limit of detection may facilitate immediate rule-out of myocardial infarction, but otherwise testing at least 3 hours from symptom onset is needed with the optimal time to rule-in myocardial infarction being 7–12 hours from the onset of symptoms.

Funding Acknowledgement

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): British Heart Foundation (BHF)Medical Research council UK (MRC)

Sex-differences in oral anticoagulation therapy in patients hospitalised with atrial fibrillation: a nationwide cohort study

Background

Important disparities in the treatment and outcomes of women and men with atrial fibrillation are well recognized. Whether introduction of direct oral anticoagulants has reduced disparities in treatment is uncertain.

Methods

All patients who had an incident hospitalization from 2010 to 2019 with non-valvular atrial fibrillation in Scotland were included in this cohort study. Community drug dispensing data were used to determine prescribed oral anticoagulation therapy and comorbidity status. Logistic regression modelling was used to evaluate patient factors associated with treatment with vitamin K antagonists and direct oral anticoagulants.

Results

A total of 172,989 patients (48% women [82,833/172,989]) had an incident hospitalization with non-valvular atrial fibrillation in Scotland between 2010 and 2019. The proportion of patients with thromboembolic risk factors (CHA2DS2VASc score >0 in men and >1 in women) treated with oral anticoagulation therapy increased from 36.8% to 66.3% over this 10-year period. By 2019, factor Xa inhibitors accounted for 83.6% of all oral anticoagulants prescribed, while treatment with vitamin K antagonists and direct thrombin inhibitors declined to 15.9% and 0.6%, respectively. Women were less likely to be prescribed any oral anticoagulation therapy compared to men (adjusted odds ratio, aOR 0.68 [95% CI, CI 0.67–0.70]). This disparity was mainly attributed to vitamin K antagonists (aOR 0.68 [95% CI 0.66–0.70]), whilst there was less disparity in use of factor Xa inhibitors between women and men (aOR 0.92 [95% CI 0.90–0.95]). At 1 year following hospitalization with atrial fibrillation, patients not prescribed oral anticoagulation therapy were more likely to have subsequent major adverse cardiovascular events compared to those prescribed with oral anticoagulation therapy (38.8% [15,380/39,608] versus 17.0% [6,761/39,671] in women and 35.2% [12,977/36,868] versus 16.4% [7,395/45,093] in men).

Conclusions

Women with non-valvular atrial fibrillation were significantly less likely to be prescribed vitamin K antagonists compared to men. Most patients admitted to hospital in Scotland with incident non-valvular atrial fibrillation are now treated with factor Xa inhibitors and this is associated with less treatment disparities between women and men.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): This study was supported by the British Heart Foundation through a Clinical Research Training Fellowship (FS/18/25/33454), Intermediate Clinical Research Fellowship (FS/19/17/34172), Senior Clinical Research Fellowship (FS/16/14/32023) and a Research Excellence Award (RE/18/5/34216), and a research grant to NHS Lothian from Bristol Myers Squibb Pharmaceuticals Ltd and Pfizer UK Ltd.

Machine learning to optimise use of cardiac troponin in the diagnosis of acute myocardial infarction

Background

Guidelines recommend fixed cardiac troponin thresholds for the assessment of patients with suspected acute coronary syndrome, however, performance varies in important patient groups as concentrations are influenced by age, sex and comorbidities. This limitation can be addressed using machine learning algorithms.

Methods

Machine learning algorithms were developed that integrate cardiac troponin concentrations at presentation or on serial testing with age, sex and clinical features in 10,038 consecutive emergency patients with suspected acute coronary syndrome. The primary outcome was an adjudicated diagnosis of type 1, type 4b or type 4c myocardial infarction. The best performing algorithm was selected for the CoDE-ACS (Collaboration for the Diagnosis and Evaluation of Acute Coronary Syndrome) decision-support tool, and performance was externally validated in 3,035 patients pooled from three prospective studies.

Findings

CoDE-ACS had excellent discrimination and calibration using cardiac troponin at presentation (area under curve [AUC] 0.959, 95% confidence interval 0.948–0.971, Brier score 0.040), in the pooled external validation cohort. At presentation, the rule-out score identified 62.1% (1,885/3,035) of all patients as low-probability of myocardial infarction with a 99.5% (99.1–99.7%) negative predictive value and 97.0% (96.3–97.6%) sensitivity. The rule-in score identified 8.3% (252/3,035) of patients as high-probability with an 83.7% (82.4–85.0%) positive predictive value and 98.5% (98.0–98.9%) specificity. Performance of the rule-out and rule-in scores was consistent across patient subgroups (Figure 1 and Figure 2). CoDE-ACS incorporating a second cardiac troponin measurement also had excellent discrimination and calibration (AUC 0.971 [0.962–0.980], Brier score 0.039) and refined the individualised probabilities in the 29.5% (898/3,035) of patients neither ruled-out or ruled-in at presentation to guide further investigation.

Conclusions

We developed and externally validated the CoDE-ACS decision-support tool using machine learning to aid in the diagnosis of myocardial infarction. CoDE-ACS had excellent diagnostic performance to rule-out and rule-in myocardial infarction at presentation, performed consistently across patient subgroups, and provided individualised probabilities to guide further care in those who require serial troponin measurements.

Conclusions

We developed and externally validated the CoDE-ACS decision-support tool using machine learning to aid in the diagnosis of myocardial infarction. CoDE-ACS had excellent diagnostic performance to rule-out and rule-in myocardial infarction at presentation, performed consistently across patient subgroups, and provided individualised probabilities to guide further care in those who require serial troponin measurements.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): National Institute for Health ResearchBritish Heart Foundation

Implementation of high-sensitivity cardiac troponin and risk of myocardial infarction or death at 5 years: a stepped-wedge cluster-randomised controlled trial

Background

Implementation of a high-sensitivity cardiac troponin I assay with the sex-specific 99th centile as the diagnostic threshold identifies more patients with myocardial injury and infarction, but whether this impacts on long-term clinical outcomes is unknown.

Purpose

In a prespecified analysis of a stepped-wedge cluster-randomised controlled trial performed across ten hospitals in Scotland, we evaluated the impact of implementing a high-sensitivity cardiac troponin I assay on outcomes at 5 years in consecutive patients with suspected acute coronary syndrome.

Methods

Throughout the trial, all 48,282 patients had cardiac troponin I concentrations measured using both a contemporary (standard care) and high-sensitivity (implementation) assay. During standard care, results from the high-sensitivity assay were concealed and the contemporary assay was used to guide care. Hospitals were randomly allocated to early (n=5) or late (n=5) implementation of the high-sensitivity assay using the sex-specific 99th centile to guide care and results from the contemporary assay were concealed. Patients reclassified by the high-sensitivity assay were defined as those with cardiac troponin concentrations above the sex-specific 99th centile but below the contemporary assay diagnostic threshold. Subsequent myocardial infarction or all-cause death at 5 years was compared before and after implementation using an adjusted Cox proportional hazards model in those reclassified by the high-sensitivity assay and stratified by index diagnosis.

Results

Overall, 10,360 patients had cardiac troponin concentrations greater than the sex-specific 99th centile of whom 1,771 (17%) were reclassified by the high-sensitivity assay. Compared to those identified as having elevated cardiac troponin by the contemporary assay, patients reclassified by the high-sensitivity assay were more likely to have non-ischemic myocardial injury (54% versus 28%) and less likely to have type 1 myocardial infarction (33% versus 59%; P<0.001 for both). In those reclassified, the 5-year incidence of subsequent myocardial infarction or all-cause death was 63% (456/720) before and 54% (567/1051) after implementation of the high-sensitivity assay (adjusted hazard ratio [aHR] 0.75 [95% CI 0.57–0.98]) (Figure 1). Following implementation, subsequent myocardial infarction or all-cause death at 5 years was reduced in patients with non-ischemic myocardial injury (aHR 0.66 [0.51–0.86]) but not type 1 or type 2 myocardial infarction (aHR 0.90 [0.78–1.03] and 0.81 [0.55–1.20], respectively).

Conclusions

In patients with suspected acute coronary syndrome, implementation of a high-sensitivity cardiac troponin assay was associated with a lower risk of subsequent myocardial infarction or death at 5 years. Improvements in outcome were greater in those with a diagnosis of non-ischemic myocardial injury rather than infarction.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): British Heart Foundation

Machine learning to aid in the diagnosis of acute heart failure in the emergency department

Background

B-type natriuretic peptide (BNP) and mid-regional pro-atrial natriuretic peptide (MRproANP) testing are recommended to aid in the diagnosis of acute heart failure. However, the application of these biomarkers for optimal diagnostic performance is uncertain.

Methods

We performed a systematic review and harmonised individual patient-level data to evaluate the diagnostic performance of BNP and MRproANP for the diagnosis of acute heart failure using random-effects meta-analysis. We subsequently developed and externally validated a decision-support tool called CoDE-HF for both BNP and MRproANP that combines the natriuretic peptide concentrations with clinical variables using machine learning to report the probability of acute heart failure for an individual patient.

Results

Fourteen studies from 12 countries provided individual patient-level data in 8,493 patients for BNP and 3,847 patients for MRproANP, in whom, 48.3% (4,105/8,493) and 41.3% (1,611/3899) had an adjudicated diagnosis of acute heart failure, respectively. The negative and positive predictive values of guideline-recommended thresholds for BNP (100 pg/mL) and MR-proANP (120 pg/mL) were 93.6% (95% confidence interval 88.4–96.6%) and 68.8% (62.9–74.2%), and 95.6% (92.2–97.6%) and 64.8% (56.3–72.5%), respectively. However, we observed significant heterogeneity in the diagnostic performance across important patient subgroups (Figure 1). In the external validation cohort, CoDE-HF was well calibrated with excellent discrimination in those without prior acute heart failure for both BNP and MRproANP (area under the curve of 0.946 [0.933–0.958] and 0.943 [0.921–0.964], and Brier scores of 0.105 and 0.073, respectively). CoDE-HF performed consistently across all subgroups for both BNP and MRproANP, and identified 30% and 65.7% at low-probability (negative predictive value of 99.1% [98.8–99.3%] and 99.1% [98.8–99.4%]), and 30% and 17.3% at high-probability (positive predictive value of 91.3% [90.7–91.9%] and 70.0% [68.5–71.4%]) in those without prior heart failure, respectively (Figure 2).

Conclusion

In an international collaborative analysis, we observed that guideline-recommended thresholds for BNP and MRproANP to diagnose acute heart failure varied significantly across patient subgroups. A decision-support tool using machine learning to combine natriuretic peptides as a continuous measure and other clinical variables provides a more accurate and individualised approach.

Funding Acknowledgement

Type of funding sources: Other. Main funding source(s): Medical Research Council and British Heart Foundation Figure 1. NPV of BNP threshold (100 pg/mL)Figure 2. NPV of the CoDE-HF rule-out score

The impact of age on the diagnosis of type 1 myocardial infarction using high-sensitivity cardiac troponin

Background

Cardiac troponin concentrations are influenced by age and comorbidities with values above the 99th centile diagnostic threshold more common in older patients without myocardial infarction. Despite this, rule-in thresholds for myocardial infarction are applied universally regardless of age or comorbidities.

Purpose

We sought to evaluate how age and cardiovascular comorbidities influence the diagnostic performance of high-sensitivity cardiac troponin I for myocardial infarction.

Methods

In a secondary analysis of a multi-centre randomised controlled trial, we identified 45,991 consecutive patients with suspected acute coronary syndrome without ST-segment elevation myocardial infarction. The diagnostic performance of high-sensitivity cardiac troponin I measured at presentation for type 1 myocardial infarction was evaluated for the sex-specific 99th centile and thresholds three and five times this value in patients stratified by age (under 50 years, between 50 and 75 years, and over 75 years). The effect of comorbidities on diagnostic accuracy was evaluated using regression modelling.

Results

Of the 45,991 patients, 8,187 (18%) had myocardial injury of which 7,677 (94%) had a presentation troponin above the sex-specific 99th centile. Mean age of those with myocardial injury was 74 years (range 18–108). The positive predictive value (PPV) of the 99th centile was 54.6% (95% confidence interval [CI] 50.6–58.8%), 58.8% (56.9–60.6%) and 36.6% (35.1–38.2%) in patients under 50 years, between 50 and 75 years, and over 75 years, respectively. Rule-in thresholds three and five-times the 99th centile gave a higher PPV in all age groups with a PPV of 45.5% (43.1–47.8%) and 50.4% (47.6–53.2%), respectively in those aged over 75 years (Table 1). Regardless of threshold, specificity and PPV was lowest in patients over 75 years and decreased with advancing age (Figure 1). Across all age groups, the presence of heart failure resulted in the greatest decrease in PPV (36.9% [34.6–39.2%] versus 50.6% [49.3–51.8%]). Adjusting for cardiovascular comorbidities resulted in modest change in the discrimination of cardiac troponin for myocardial infarction (area under curve 0.89 vs 0.90) and did not prevent a decline in diagnostic accuracy in older patients.

Conclusion

The specificity and PPV of high-sensitivity cardiac troponin I for myocardial infarction decreases with advancing age. Cardiovascular comorbidities impact the PPV of troponin, but do not explain the decline in diagnostic accuracy with age. Clinicians should be aware of these important differences in performance by age of the diagnostic and rule-in thresholds for myocardial infarction when interpreting troponin results in older patients.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): University of Edinburgh Figure 1

Troponin to risk stratify patients with suspected acute coronary syndrome for computed tomography coronary angiography

Background

Patients with suspected acute coronary syndrome in whom myocardial infarction has been ruled-out are at risk of future adverse cardiac events. However, the optimal approach to risk stratify and investigate these patients is uncertain.

Methods

We performed a prospective cohort study of 250 patients presenting to the Emergency Department with suspected acute coronary syndrome and troponin concentrations below the sex-specific 99th centile (16 ng/L for women and 34 ng/L for men). Patients were recruited in a 2:1 fashion stratified by peak high-sensitivity cardiac troponin I concentration above and below the early rule-out threshold of 5 ng/L (167 patients with intermediate troponin concentrations between 5 ng/L and the sex-specific 99th centile threshold and 83 patients with troponin concentrations <5 ng/L). All patients underwent computed tomography coronary angiography after they were discharged from hospital.

Results

Overall, 37.6% (94/250) of patients had normal coronary arteries whilst 36.0% (90/250) and 26.4% (66/250) had non-obstructive and obstructive coronary artery disease, respectively. Patients with intermediate troponin concentrations were more likely to have coronary artery disease than those with troponin concentrations <5 ng/L (71.9% [120/167] versus 43.4% [36/83]; odds ratio 3.33 [95% confidence interval 1.92–5.78]). This association persisted irrespective of whether patients had anginal symptoms. Conversely, there was no difference in the prevalence of coronary artery disease between those with and without anginal symptoms (63.2% [67/106] and versus 61.8% [89/144]; odds ratio 0.92 [0.48–1.76]). The majority of patients found to have coronary artery disease did not have a prior diagnosis and were not on optimal preventative medical therapy prior to undergoing computed tomography coronary angiography (50.8% [61/120] and 61.0% [22/36], versus 61.7% [74/120] and 69.4% [25/36] in patients with intermediate versus low troponin concentrations, respectively).

Conclusions

In patients with suspected acute coronary syndrome who have myocardial infarction ruled out, those with intermediate cardiac troponin concentrations are three-times more likely to have coronary artery disease than those with low troponin concentrations. Conversely anginal symptoms did not discriminate between those with and without coronary artery disease. Further studies are required to determine if targeting computed tomography coronary angiography to those with intermediate cardiac troponin concentrations can improve the use of preventative medical therapies and clinical outcomes.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): The British Heart Foundation Odds ratio of coronary artery diseaseCumulative proportion with CAD

N-terminal pro-B-type natriuretic peptide in the diagnosis of acute heart failure

Background

N-terminal pro-B-type natriuretic peptide (NT-proBNP) testing can aid in the evaluation of patients with suspected acute heart failure. Current approaches are based on thresholds selected to give good negative and positive predictive value, however the optimal means to utilise NT-proBNP is uncertain.

Methods

Embase, Medline and Cochrane central register of controlled trials were searched for studies evaluating NT-proBNP in patients with suspected acute heart failure. Individual patient-level data was requested and diagnostic performance for the guideline-recommended rule-out (300 pg/mL) and age-specific rule-in (450, 900 and 1,800 pg/mL) thresholds were evaluated with random-effects meta-analysis. A generalised linear mixed model was developed and validated as a decision-support tool that combines NT-proBNP with clinical characteristics to report the probability of acute heart failure (0–100) for an individual patient.

Results

Fourteen studies from 13 countries provided individual patient-level data in 10,365 patients, of which, 43.9% (4,549/10,365) had an adjudicated diagnosis of acute heart failure. At the rule-out threshold, the negative predictive value (NPV) was 94.6% (91.9%-96.4%), with significant heterogeneity across patient subgroups (see Figure). At the rule-in thresholds, the positive predictive values (PPV) for those <50 years, 50–75 years, and >75 years were 61.0% (55.3%-66.4%), 72.7% (62.1%-81.3%) and 80.5% (71.1%-87.4%), respectively. In patients without prior heart failure, our model had good discrimination and calibration (area under the curve of 0.931 [0.925–0.938], Brier score of 0.094). A score of <5.6 and ≥45.2 identified 42.3% of patients as low-probability of acute heart failure (NPV 98.5%, 97.6%-99.1%) and 30.5% as high-probability (PPV 75.1%, 67.7%-81.3%) with consistent performance across subgroups.

Conclusions

The diagnostic performance of NT-proBNP thresholds to rule-out and rule-in acute heart failure varies across patient subgroups. A model that uses NT-proBNP as a continuous measure provides a more consistent and individualised approach.

NPV of NT-proBNP threshold of 300 pg/mL

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): British Heart Foundation

Validation of a machine learned model to predict the diagnosis of myocardial infarction

Introduction

The myocardial-ischemic-injury-index (MI3) is a promising machine learned algorithm that predicts the likelihood of myocardial infarction in patients with suspected acute coronary syndrome. Whether this algorithm performs well in unselected patients or predicts recurrent events is unknown.

Methods

In an observational analysis from a multi-centre randomised trial, we included all patients with suspected acute coronary syndrome and serial high-sensitivity cardiac troponin I measurements without ST-segment elevation myocardial infarction. Using gradient boosting, MI3 incorporates age, sex, and two troponin measurements to compute a value (0–100) reflecting an individual's likelihood of myocardial infarction, and estimates the negative predictive value (NPV) and positive predictive value (PPV). Model performance for an index diagnosis of myocardial infarction, and for subsequent myocardial infarction or cardiovascular death at one year was determined using previously defined low- and high-probability thresholds (1.6 and 49.7, respectively).

Results

In total 20,761 of 48,282 (43%) patients (64±16 years, 46% women) were eligible of whom 3,278 (15.8%) had myocardial infarction. MI3 was well discriminated with an area under the receiver-operating-characteristic curve of 0.949 (95% confidence interval 0.946–0.952) identifying 12,983 (62.5%) patients as low-probability (sensitivity 99.3% [99.0–99.6%], NPV 99.8% [99.8–99.9%]), and 2,961 (14.3%) as high-probability (specificity 95.0% [94.7–95.3%], PPV 70.4% [69–71.9%]). At one year, subsequent myocardial infarction or cardiovascular death occurred more often in high-probability compared to low-probability patients (17.6% [520/2,961] versus 1.5% [197/12,983], P<0.001).

Conclusions

In unselected consecutive patients with suspected acute coronary syndrome, the MI3 algorithm accurately estimates the likelihood of myocardial infarction and predicts probability of subsequent adverse cardiovascular events.

Performance of MI3 at example thresholds

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Medical Research Council