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Author Interview: Dr. Richard Body, MB ChB MRCSEd(A&E) FCEM PhD
NIHR Clinical Lecturer, Emergency/Cardiovascular Medicine
Cardiovascular Sciences Research Group, The University of Manchester
and Emergency Department, Manchester Royal Infirmary
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Publication:
Author Interview: Dr. Richard Body
Rapid Exclusion of Acute Myocardial Infarction in Patients With Undetectable Troponin Using a High-Sensitivity Assay
Body, Richard, Carley, Simon, McDowell, Garry, Jaffe, Allan S., France, Michael, Cruickshank, Kennedy, Wibberley, Christopher, Nuttall, Michelle, Mackway-Jones, Kevin
J Am Coll Cardiol 2011 58: 1332-1339
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What are the main findings of the study?
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The study demonstrates that high sensitivity troponin T using the Roche Elecsys assay can be used to immediately rule out a diagnosis of acute myocardial infarction in many patients presenting to the emergency department. These patients would not need to undergo serial troponin testing, as we do currently. They could be reassured that they do not have an acute myocardial infarction at an earlier stage and it may be possible to reduce unnecessary hospital admissions.
We achieved this by using a lower troponin cut-off than usual.
The conventional cut-off for diagnosis is set at the 99th percentile of troponin levels in healthy individuals. We set a lower ‘rule out’ cut-off at the lower detection limit (or ‘limit of blank’) of the assay. In an initial cohort study, we found that no patients with initially undetectable (<3ng/L) high sensitivity troponin T had an acute myocardial infarction, giving a sensitivity of 100%. Subsequently, we implemented the assay in practice and evaluated whether any patients with an initially undetectable (<3ng/L) troponin T developed a subsequent elevation (above the 99th percentile) on serial testing. Of 915 patients who underwent serial troponin testing, only one patient with initially undetectable troponin, who presented within an hour of symptom onset, developed a subsequent elevation.
The negative predictive value of an initially undetectable high sensitivity troponin T was therefore 99.4%, which is considerably higher than many investigations that are currently used in clinical practice.
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Were any of the findings unexpected?
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We knew that our strategy of adopting a novel ‘rule out’ cut-off had great potential from looking at the publication by Reichlin et al in 2009 (1). In the web only appendix, Reichlin published data demonstrating that the sensitivity of the Roche assay at the ‘limit of blank’ was 100%.
Further, in a study of 137 patients, Christ et al (2) also reported that undetectable high sensitivity troponin T levels had a negative predictive value of 100%. Our findings, from two cohorts of 703 and 915 patients, therefore serve to confirm the findings presented in secondary analyses of previous studies, giving greater weight to our conclusions.
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What should clinicians and patients take away from this study?
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Patients with initially undetectable high sensitivity troponin T levels are extremely unlikely to be having an acute myocardial infarction. We would still like to further validate our findings before suggesting that all of these patients can be discharged from hospital. However, it is clear for now that our findings can help to make more judicious use of healthcare resources and avoid unnecessary treatment for patients.
Patients with high sensitivity troponin T <3ng/L are unlikely to benefit from intensive anti-platelet treatment (with clopidogrel, prasugrel or ticagrelor) and anti-thrombotic treatment (low molecular weight heparin, fondaparinux). Depending on the clinical context, these patients are also likely to be suitable for investigation in a low dependency environment such as an emergency department observation unit.
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What recommendations do you have for nephrology health care providers as a result of your study?
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Unless time from symptom onset is less than an hour, it seems that high sensitivity troponin T <3ng/L rules out an acute myocardial infarction in the emergency department. For now, I would still advocate serial testing for these patients, pending further validation.
However, these patients are very unlikely to benefit from intensive anti-platelet or anti-thrombotic treatment, thus reducing the need for unnecessary treatment. Depending on clinical context, they are likely to be suitable for investigation in a low dependency environment. If the findings are validated again by further research, many unnecessary hospital admissions will also be avoided
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Abstract: |
Objectives: This paper sought to evaluate whether high sensitivity troponin (hs-cTnT) can immediately exclude acute myocardial infarction (AMI) at a novel ‘rule out' cut-off.
Background: Subgroup analysis of recent evidence suggests that undetectable hs-cTnT may exclude AMI at presentation.
Methods: In a cohort study, we prospectively enrolled patients with chest pain, evaluating them with standard troponin T and testing for hs-cTnT (Roche Diagnostics, Basel, Switzerland) at presentation. The primary outcome was a diagnosis of AMI. We also followed up patients for adverse events within 6 months. After subsequent clinical implementation of hs-cTnT, we again evaluated whether initially undetectable hs-cTnT ruled out a subsequent rise.
Results: Of 703 patients in the cohort study, 130 (18.5%) had AMI, none of whom initially had undetectable hs-cTnT (sensitivity: 100.0%, 95% confidence interval [CI]: 95.1% to 100.0%, negative predictive value: 100.0%, 95% CI: 98.1% to 100.0%). This strategy would rule out AMI in 27.7% of patients, 2 (1.0%) of whom died or had AMI within 6 months (1 periprocedural AMI, 1 noncardiac death). We evaluated this approach in an additional 915 patients in clinical practice. Only 1 patient (0.6%) with initially undetectable hs-cTnT had subsequent elevation (to 17 ng/l), giving a sensitivity of 99.8% (95% CI: 99.1% to 100.0%) and a negative predictive value of 99.4% (95% CI: 96.6% to 100.0%).
Conclusions: Undetectable hs-cTnT at presentation has very high negative predictive value, which may be considered to rule out AMI, identifying patients at low risk of adverse events. Pending further validation, this strategy may reduce the need for serial testing and empirical treatment, enabling earlier reassurance for patients and fewer unnecessary evaluations and hospital admissions.
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Reference List
1. Reichlin T, Hochholzer W, Bassetti S, et al. Early diagnosis of myocardial infarction with sensitive cardiac troponin assays. New England Journal of Medicine 2009; 361:858-67.
2. Christ M, Popp S, Pohlmann H, et al. Implementation of high sensitivity cardiac troponin T measurement in the emergency department. American Journal of Medicine 2010; 123:1134-42. |
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Featured Angina| Acute Coronary Syndrome and Heart Disease Interviews
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Highlights of Article by Dr. Erik Hess et of Mayo Clinic ;CIRCOUTCOMES 2012
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Chest pain is the 2nd most common reason patients come to EDs across the United States
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Initial testing – including information obtained from the history, physical exam, electrocardiogram, and cardiac troponin – identifies > 98% of heart attacks
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To avoid missing a diagnosis of heart attack or pre-heart attack symptoms, emergency physicians often admit patients to observation units or to the hospital for extensive diagnostic testing, including stress testing
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This results in false positive test results, unnecessary exposure to radiation, and unnecessary downstream procedures such as stent placement in arteries of the heart
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Decision aids are evidence-based tools designed to educate and engage patients in decisions regarding their care
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We hypothesized that patients who were educated regarding their future risk for a heart attack and engaged in the decision of whether to be admitted to the observation unit for stress testing or to follow-up with a Mayo Clinic heart doctor in the next 72 hours would have greater knowledge about their short-term risk for heart attack, be more aware of the management options, and choose less intensive approaches to evaluation
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We randomly assigned 204 patients who came to the ED with chest pain and were being considered for observation unit admission to the decision aid or to usual care
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Decision aid patients:
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Had greater knowledge regarding their short-term risk for a heart attack
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Less frequently decided to be admitted to the observation unit for stress testing
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Had 4 times greater engagement in the decision making process
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Had no adverse events within 30 days of the ED visit
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Take home points
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Patients want to be educated and engaged in decisions regarding their care
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Once properly informed and engaged in treatment decisions, patients often choose less intensive treatment options
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Integrated health systems like the Mayo Clinic in which physicians collaboratively work together to provide ER patients ready access to outpatient follow-up have potential to improve the value of Emergency care
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Glucose, Insulin and Potassium (“GIK”) TO MINIMIZE IMPACT OF HEART ATTACKS BEFORE PATIENTS GET TO THE HOSPITAL
Study puts life-saving drugs in the hands of paramedics, decreasing rate of cardiac arrest and death from heart attacks
CHICAGO (March 27, 2012) — Paramedics can potentially reduce someone’s chances of having a cardiac arrest or dying by 50 percent by immediately administering a mixture of glucose, insulin and potassium (“GIK”) to people having a heart attack, according to research presented today at the American College of Cardiology’s 61st Annual Scientific Session. The Scientific Session, the premier cardiovascular medical meeting, brings cardiovascular professionals together to further advances in the field.
The study showed that patients who received GIK immediately after being diagnosed with acute coronary syndrome — which indicates a possible heart attack is either in progress or on the way — were 50 percent less likely to have cardiac arrest (a condition in which the heart suddenly stops beating) or die than those who received a placebo, although the treatment did not prevent the heart attack from occurring. The reduction in in-hospital cardiac arrest or death was a “secondary endpoint”, so statistically was not definitive, but was consistent with how GIK seems to work in experimental models of heart attack.
The effect was also present for patients with ST-elevation heart attacks, which require immediate treatment. For those patients, immediate GIK was associated with a 60 percent reduction in in-hospital cardiac arrest or death.
“When started immediately in the home or on the way to the hospital — even before the diagnosis is completely established — GIK appears not completely prevent any heart attack from occurring, but appeared in this trial to reduce the size of heart attacks and to reduce by half the risk of having a cardiac arrest or dying,” said Harry P. Selker, MD, MSPH, executive director of the Institute for Clinical Research and Health Policy Studies at Tufts Medical Center, who led the study with Joni Beshansky, RN, MPH, co-principal investigator and project director. “Acute coronary syndromes represent the largest cause of death in this country. GIK is a very inexpensive treatment that appears to have promise in reducing those deaths and morbidity.”
The cost of the treatment is about $50.
“Because the trial is the first to show GIK could be effective when used by paramedics in real-world community settings, it could have important implications for the treatment of heart attacks,” Dr. Selker said. Previous clinical trials have shown no consistent effect, likely because the GIK was given too late to help. This study, the “IMMEDIATE Trial,” was the first to test the effectiveness of administering GIK at the very first signs of a threatening heart attack, in the community, rather than waiting hours until the diagnosis was well-established at a hospital, as done in previous clinical trials.
“We wanted to do something that is effective and can be used anywhere,” said Dr. Selker. “We’ve done a lot of studies of acute cardiac care in emergency departments and hospitals, but more people die of heart attacks outside the hospital than inside the hospital. Hundreds of thousands of people per year are dying out in the community; we wanted to direct our attention to those patients.”
The researchers trained paramedics in 36 Emergency Medical Services systems in 13 cities across the country to administer GIK after determining that a patient was likely having a threatened or already established heart attack using electrocardiograph-based ACI-TIPI (acute cardiac ischemia time-insensitive predictive instrument) and thrombolytic predictive instrument decision support that prints patient-specific predictions on the top of an electrocardiogram. The paramedics used these predictions to decide if a patient would likely benefit from treatment. There were 911 patients randomized to receive either the GIK treatment or a placebo.
Administering GIK immediately also reduced the severity of the damage to the heart tissue from the heart attack. On average, 2 percent of the heart tissue was destroyed by the heart attack in people receiving GIK, compared with 10 percent in those who received the placebo. Although a significant proportion of suspected heart attacks are later determined to be false alarms (23 percent in this study), administering GIK does not appear to cause any harmful effects in such patients.
The research team will follow up with study participants at six and 12 months to evaluate the longer-term benefit of the GIK treatment.
This study was funded by the NIH’s National Heart, Lung and Blood Institute.
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Amazon.com 's Editorial Reviews
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Part of the award winning public television series Healthy head
/Healthy Mind. It's one of the scariest medical symptoms for people who are generally healthy: a tightening, painful feeling in the chest known as Angina. In some cases this chest pain can be a serious warning that requires immediate treatment. But for the millions of people with chronic, stable angina the discomfort is something that can be readily managed with a variety of treatments. In this program we take a look at what generally causes angina, what can be done to prevent it and how it can be effectively treated with lifestyle changes, innovative drug therapies and medical procedures.
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Amazon.com Editorial Review:
Philips HeartStart Home Defibrillator (AED)
Be prepared for the unexpected.
When sudden cardiac arrest (SCA) strikes, the electrical system of the heart short circuits, causing the heart to quiver rather than pump in a normal rhythm. It typically results in the abnormal heart rhythm know as ventricular fibrillation (VF). It usually happens without warning and the majority of people have no previously recognized symptoms of heart disease. And it most often happens at home. For the best chance of survival from SCA caused by VF, a defibrillator should be used within 5 minutes. Yet, less than 1 in 20 people survive largely because a defibrillator does not arrive in time.
Just as seat belts or airbags do not save every life in a traffic accident, a defibrillator will not save every person who suffers a sudden cardiac arrest. Yet many lives could be saved if more people could be reached more quickly.
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