The Early Predictive Ability of Myoglobin versus Troponin in Patients Presenting to the Emergency Department With Suspected Acute Coronary Syndrome

BackgroundMyoglobin is a component of cardiac muscle that is released upon injury and has been used as a biomarker for cardiac injury. Older literature reported that myoglobin concentrations may rise prior to other commercially available biomarkers in the setting of an acute myocardial infarction and may be more sensitive in detecting recent cardiac injury. In our institution, we routinely include myoglobin assays along with assays for troponin and creatinine phosphokinase as a panel test as suggested by McCord in 2003. However, with the increasing sensitivity of troponin testing over the past decade, many institutions no longer use myoglobin testing to detect recent cardiac injury.Study ObjectiveTo determine the utility of serum myoglobin levels versus troponin levels in detecting acute myocardial injury in patients presenting to the emergency department (ED) with symptoms suggestive of acute coronary syndrome.MethodsWe performed an IRB-approved retrospective chart review of all ED patients who had cardiac biomarker tests performed over a nine-month period in 2012 at a suburban tertiary care hospital (an annual census over 85,000 patients). Subjects were identified through laboratory query of all patients who had successive cardiac biomarkers panels which included serial myoglobin and troponin tests obtained over two consecutive days. We obtained patient demographics, hospital course metrics, and discharge. We identified subjects who had an initial elevated myoglobin result with an initial normal troponin results. We specifically reviewed all charts who had elevated troponin testing within 24-48 hours. We used descriptive statistics to analyze the data.ResultsDuring the nine-month period, 240 subjects had two sets of cardiac biomarker measured. In 7 of the 240 cases (2.9%), troponin levels were elevated in subsequent testing and myoglobin levels remained abnormal. None of the 7 had electrocardiograms that triggered immediate thrombolytics or immediate angiography. Only 1 of these cases underwent coronary angiography and was subsequently found to have a significant occlusion (100% occlusion of an obtuse marginal artery). The remaining 6 cases either underwent coronary angiography and no new lesion was found or they were not candidates for catheterization.ConclusionsA previous study by McCord in 2003 found a rate of 16.6% (14 of 84 cases) for patients presenting to the ED that had elevated myoglobin levels without elevated troponin levels and had a final diagnosis of myocardial infarction. Our study demonstrates a rate of 2.9% for patients with a positive myoglobin in the setting of an initially negative troponin. These results suggest improved sensitivity of serum troponin tests for detecting myocardial injury and raise the question of whether serum myoglobin levels should be routinely measured in cases of suspected acute coronary syndrome. BackgroundMyoglobin is a component of cardiac muscle that is released upon injury and has been used as a biomarker for cardiac injury. Older literature reported that myoglobin concentrations may rise prior to other commercially available biomarkers in the setting of an acute myocardial infarction and may be more sensitive in detecting recent cardiac injury. In our institution, we routinely include myoglobin assays along with assays for troponin and creatinine phosphokinase as a panel test as suggested by McCord in 2003. However, with the increasing sensitivity of troponin testing over the past decade, many institutions no longer use myoglobin testing to detect recent cardiac injury. Myoglobin is a component of cardiac muscle that is released upon injury and has been used as a biomarker for cardiac injury. Older literature reported that myoglobin concentrations may rise prior to other commercially available biomarkers in the setting of an acute myocardial infarction and may be more sensitive in detecting recent cardiac injury. In our institution, we routinely include myoglobin assays along with assays for troponin and creatinine phosphokinase as a panel test as suggested by McCord in 2003. However, with the increasing sensitivity of troponin testing over the past decade, many institutions no longer use myoglobin testing to detect recent cardiac injury. Study ObjectiveTo determine the utility of serum myoglobin levels versus troponin levels in detecting acute myocardial injury in patients presenting to the emergency department (ED) with symptoms suggestive of acute coronary syndrome. To determine the utility of serum myoglobin levels versus troponin levels in detecting acute myocardial injury in patients presenting to the emergency department (ED) with symptoms suggestive of acute coronary syndrome. MethodsWe performed an IRB-approved retrospective chart review of all ED patients who had cardiac biomarker tests performed over a nine-month period in 2012 at a suburban tertiary care hospital (an annual census over 85,000 patients). Subjects were identified through laboratory query of all patients who had successive cardiac biomarkers panels which included serial myoglobin and troponin tests obtained over two consecutive days. We obtained patient demographics, hospital course metrics, and discharge. We identified subjects who had an initial elevated myoglobin result with an initial normal troponin results. We specifically reviewed all charts who had elevated troponin testing within 24-48 hours. We used descriptive statistics to analyze the data. We performed an IRB-approved retrospective chart review of all ED patients who had cardiac biomarker tests performed over a nine-month period in 2012 at a suburban tertiary care hospital (an annual census over 85,000 patients). Subjects were identified through laboratory query of all patients who had successive cardiac biomarkers panels which included serial myoglobin and troponin tests obtained over two consecutive days. We obtained patient demographics, hospital course metrics, and discharge. We identified subjects who had an initial elevated myoglobin result with an initial normal troponin results. We specifically reviewed all charts who had elevated troponin testing within 24-48 hours. We used descriptive statistics to analyze the data. ResultsDuring the nine-month period, 240 subjects had two sets of cardiac biomarker measured. In 7 of the 240 cases (2.9%), troponin levels were elevated in subsequent testing and myoglobin levels remained abnormal. None of the 7 had electrocardiograms that triggered immediate thrombolytics or immediate angiography. Only 1 of these cases underwent coronary angiography and was subsequently found to have a significant occlusion (100% occlusion of an obtuse marginal artery). The remaining 6 cases either underwent coronary angiography and no new lesion was found or they were not candidates for catheterization. During the nine-month period, 240 subjects had two sets of cardiac biomarker measured. In 7 of the 240 cases (2.9%), troponin levels were elevated in subsequent testing and myoglobin levels remained abnormal. None of the 7 had electrocardiograms that triggered immediate thrombolytics or immediate angiography. Only 1 of these cases underwent coronary angiography and was subsequently found to have a significant occlusion (100% occlusion of an obtuse marginal artery). The remaining 6 cases either underwent coronary angiography and no new lesion was found or they were not candidates for catheterization. ConclusionsA previous study by McCord in 2003 found a rate of 16.6% (14 of 84 cases) for patients presenting to the ED that had elevated myoglobin levels without elevated troponin levels and had a final diagnosis of myocardial infarction. Our study demonstrates a rate of 2.9% for patients with a positive myoglobin in the setting of an initially negative troponin. These results suggest improved sensitivity of serum troponin tests for detecting myocardial injury and raise the question of whether serum myoglobin levels should be routinely measured in cases of suspected acute coronary syndrome. A previous study by McCord in 2003 found a rate of 16.6% (14 of 84 cases) for patients presenting to the ED that had elevated myoglobin levels without elevated troponin levels and had a final diagnosis of myocardial infarction. Our study demonstrates a rate of 2.9% for patients with a positive myoglobin in the setting of an initially negative troponin. These results suggest improved sensitivity of serum troponin tests for detecting myocardial injury and raise the question of whether serum myoglobin levels should be routinely measured in cases of suspected acute coronary syndrome.