- Email: [email protected]
Comparison of accuracy of plasma myoglobin and CK-MB for the diagnosis of acute myocardial infarction
RESEARCH FORUM ABSTRACTS
ters, it is also important to understand the effects of a primary change in frequency of cardiac contraction on general circulatory, dynamics. Methods: The hemodynamic parameters of stroke volume, cardiac output, pulse pressure, mean arterial pressure, and peripheral resistance were measured in chronically instrumented conscious dogs in which a pacemaker was implanted to control heart rate. After monitoring the dogs for a 24-hour control period, the heart rate was manually increased abruptly while changes in circuIatory dynamics were recorded for an additional 24 hours. Observed differences are reported as an average percent ol the 24-hour control means. Results: In 6 dogs studied, the heart rate was increased an average of 2.3-fold over the basal control level by pacing. This increase in heart rate resulted in a mean fall in stroke volume and arterial pressure by 73% and 2 0 % respectively, while peripheral resistance increased by 45%. There was also a 43% average fall in the pulse pressure while cardiac output changes were highly variable Conclusion: Although a substantial primary change in heart rate can significantly affect the stroke volume, peripheral resistance, and pulse pressure, there is a much less consequential effect on the mean arterial pressure.
189 EnhancedDiagnosisnf NarrowComplexTachycardiasUsing Increased ECG Speed
Accardi AJ, Miller R, HolmesJF/Universityof California-Davis Schoolof Medicine. Sacramento,CA Study objective: To determine whether the addition of a rapid (50-mm/s) ECG increases the diagnostic accuracy of narrow complex tachycardia when compared with standard speed (25-ram/s) ECG alone. Methods: We conducted a prospective comparative trial at a university-based urban hospital. Thirty-two ECGs with narrow complex taehycardia (heart rate range 149 to 260 beatsdmin) were printed at both 25-mm/s (standard) and 50-mm/s (rapid) speeds. Eight board-certified emergency physicians were asked to initially interpret the standard ECG (standard group). After a 2-week washout period, the same 8 participants were given both the standard and rapid speed ECGs (rapid group) for interpretation The ECG diagnosis was based on the patient's ultimate clinical diagnosis and was independently confirmed in all cases by a board-certified cardiologist masked to all clinical data The ECG distribution was as follows: atrial flutter (17), atrial fibrillation (9), paroxysmal supraventricular tachycardia (PSVT) (4), and sinus tachycardia (2). Participants were masked to the ECG ratios. We compared the diagnostic accuracy between the 2 groups" diagnoses using the Wilcoxon sign rank test. Results: Correct diagnosis of the ECG improved in the rapid ECG group compared with the standard ECG group (median 73%, 95% confidence interval [CI] 69% to 78% versus 61%, 95% CI 54% to 68%; P=.O1). The diagnosis of atrial flutter significantly improved in the rapid group compared with the standard group (median 56%, 95% CI 44% to 67% versus 44%, 95% CI 30% to 58%; P=.0I). The diagnosis of atrial fibrillation significantly improved in the rapid group compared wuh the standard group (median 100%, 95% C1 96% to 100% versus 95%, 95% CI 87% to 100%; P=.047) Conclusion: Correct diagnosis of narrow complex tachycardias was signihcantIy improved when ECGs at both 25 mm/s and 50 mm/s were used for interpretation h appears that the simple technique of speeding up the ECG paper, thus effectively spacing out the rhythm, enhances the diagnostic ability of the observer.
190
Comparisoflof Accuracy of Plasma Myogiobin and CK-MB for the Diagnosis of Acute Myocardial Infarction
Bassan R. Gamarski R. Volschan A, 8aspar S, Mohallem K, Macaciel R/Pr6-CardiacoHospital, Rio de Janeiro, Brazil Acute myocardial infarction (AMI) is diagnosed by ECG changes and/or elevated plasma cardiac markers. The enzymatic gold standard is creatine kinase izoenzyme MB (CK-MB), but new protein markers of myocardial injury' have been used recently. Myogtobin is a nonspecific cardiac protein that increases in AMI 1 to 3 hours after pain onset, therefore earlier than CK-MB, Study objective: To determine whether myoglobin is more accurate than CK-MB for the early diagnosis of AMI. Methods: In this prospective stud3,,, serial plasma myoglobin levels (baseline and 3, 6, and 9 hours after admission) were determined by immunoturbidimetry for the diagnosis of AMI in 688 consecutive patients with chest pain seen in the emergency department. Plasma CK-MB levels were simultaneously measured and the diagnosis of AMI was made in 156 patients by a typical CK-MB curve. Results: Median time of chest pain onset to hospital arrival was 2 0 hours for AMI patients Sensitivity of the first myoglohin determination for AMI was significantly better
OCTOBER 1999. PART 2 34:4 ANNALSOF EMERGENCYMEDICINE
than that of the first CK-MB le'.'el (69% versus 46%. P=.002), and this significant difference '...'asseen in lx~th early-arri',ang (<_2 hours) and fate-amving (>2 hours) patients. By the second measurement, the cumulative sensiti'~aties were similar. Predictive value of 2 consecutive normal myoglobin and CK-MB determinations was similar; a third normal measurement still did not rule out AMI 0 % and 1%, respectively) Conclusion: For early diagnosis of AMI, myoglobin is significantly better than CK.,MB. Better early sensiti,aty of single myogtobin determination is already seen after 1 hour of pain onset but not alter 5 hours (greater difference being with <_3 hours). Some patients `.vith AMI may still have normal myoglobin or CK MB levels at 6 hours, especially ,.,.hen they do not have ST elevation on admission
91 Physician Probability Estimatesfor Patients PresentingWith Chest Pain Schaider J, Reilly B, Das K, Roberts RR, Rydman RJ, EvansA/Cook County Hospital, Rush University. Chicago. IL The disposition of emergency department patients with chest pain is difficult and has a significant impact on the resource utilization of telemetry and critical care beds. Safely admitting patients to lower-Level care leads to improved resource allocation. Assessment of the nsk ot major complications (COMP), coronary' artery disease (CAD). and myocardial inlarction (MI) are important determinants in appropriate chest pain (CP) disposition decisions. Study objectives: The goal of this study was to determine physician estimates for the above 3 risk categories and to compare these estimates with the actual risks. Methods: Using published data, 20 CP patient cases were de`.'eloped such that each case represented a different combination of very" low low. moderate, and high risks based on COMP. CAD, and MI nsks. One hundred forty-seven physicians reviewed each case and assigned an estimate of risk (0 to 100%) for COMP. CAD. and MI for each of the 20 cases. Physician estimates were compared with the actual risks using stratified matched pair analysis Results: Forty-six emergency physicians, 88 internists, and 13 cardiologists revie`.ved ~be cases There were no significant differences between these groups. Overall, (or very- Iow-nsk CP patients, the estimated versus actual risks were: COMP 10% versus 060*,: CAD 38% versus <10%: MI 18% ".'ersus 2%. For Iow-nsk CP patients, the actual versus estimated risks were: COMP 17% versus 4%; CAD 49% versus 10% to 50~ MI 39% versus 14%. For moderate-risk CP patients, the actual versus estimated nsks were: COMP 21% versus 8%: CAD 68% versus 51% to 99%; MI 48% versus 25% For high-risk CP patients, the actual versus estimated risks were: COMP 42% versus 16%: CAD 75'}6 versus 100%; MI 82% versus 75%. Conclusion: For very Io'.v-risk CP patients, physicians overestimate the risk of COMP by a factor of 17, CAD by a factor of 7, and MI by a factor of 9. In addition, physicians overesumate complication risk for all nsk categories of patients complaining of chest pain. Better understanding of physician risk assessment should help to improve physician triage and admission decisions and to potentially improve resource allocation.
192
Serious Head Injury and Denth AssociatedWith the 0peration nf All-Terrain Vehicles and Motorcycles by Minors
Kapur RK, Mader TJ, Letourneau P/Baystate Medical Center. "ruffs University School of Medicine. Springfield, MA Study objective: In most US states, children younger than age 16 are not legally able to operate motor ;'ehicles independently. Despite this prohibition, many are allo`.ved to operate recreational vehicles (RVs). such as all-terrain vehicles (ATVs) and motorcycles (MCsJ. wathout adult supep,'ision In January, 1988, sale of new 3-wheel ATVs '.,,'ere banned in the United States because of the high incidence of senous injury associated with their use. The purpose of this study was to review the incidence of senous head irilUry and death associated wuh underage use of A W s and MCs. with and without helmet use, since ! ~88 Methods: This study was a , :rospective analysis of data collected (1988-1998) by the National Pediamc Trauma ICegistry (NPTR) for more than 75,000 pediatric trauma patients. There were 923 children in the database who were <16 years of age, injured or killed while operating an A1%' or MC and had data recorded on use of protective gear Patients who used and did not use helmets were descnptively compared. Results: The Table summarizes the main results. The grc,ups were similar in makeup All patients were admitted There was no difference in injury seventy by pediamc trauma score tPTS) bep.veen the 2 groups Of the 923 patients, 375 (41%) had neurologic complications from their injuries. Neurologic injuries accounted for
S 49
ters, it is also important to understand the effects of a primary change in frequency of cardiac contraction on general circulatory, dynamics. Methods: The hemodynamic parameters of stroke volume, cardiac output, pulse pressure, mean arterial pressure, and peripheral resistance were measured in chronically instrumented conscious dogs in which a pacemaker was implanted to control heart rate. After monitoring the dogs for a 24-hour control period, the heart rate was manually increased abruptly while changes in circuIatory dynamics were recorded for an additional 24 hours. Observed differences are reported as an average percent ol the 24-hour control means. Results: In 6 dogs studied, the heart rate was increased an average of 2.3-fold over the basal control level by pacing. This increase in heart rate resulted in a mean fall in stroke volume and arterial pressure by 73% and 2 0 % respectively, while peripheral resistance increased by 45%. There was also a 43% average fall in the pulse pressure while cardiac output changes were highly variable Conclusion: Although a substantial primary change in heart rate can significantly affect the stroke volume, peripheral resistance, and pulse pressure, there is a much less consequential effect on the mean arterial pressure.
189 EnhancedDiagnosisnf NarrowComplexTachycardiasUsing Increased ECG Speed
Accardi AJ, Miller R, HolmesJF/Universityof California-Davis Schoolof Medicine. Sacramento,CA Study objective: To determine whether the addition of a rapid (50-mm/s) ECG increases the diagnostic accuracy of narrow complex tachycardia when compared with standard speed (25-ram/s) ECG alone. Methods: We conducted a prospective comparative trial at a university-based urban hospital. Thirty-two ECGs with narrow complex taehycardia (heart rate range 149 to 260 beatsdmin) were printed at both 25-mm/s (standard) and 50-mm/s (rapid) speeds. Eight board-certified emergency physicians were asked to initially interpret the standard ECG (standard group). After a 2-week washout period, the same 8 participants were given both the standard and rapid speed ECGs (rapid group) for interpretation The ECG diagnosis was based on the patient's ultimate clinical diagnosis and was independently confirmed in all cases by a board-certified cardiologist masked to all clinical data The ECG distribution was as follows: atrial flutter (17), atrial fibrillation (9), paroxysmal supraventricular tachycardia (PSVT) (4), and sinus tachycardia (2). Participants were masked to the ECG ratios. We compared the diagnostic accuracy between the 2 groups" diagnoses using the Wilcoxon sign rank test. Results: Correct diagnosis of the ECG improved in the rapid ECG group compared with the standard ECG group (median 73%, 95% confidence interval [CI] 69% to 78% versus 61%, 95% CI 54% to 68%; P=.O1). The diagnosis of atrial flutter significantly improved in the rapid group compared with the standard group (median 56%, 95% CI 44% to 67% versus 44%, 95% CI 30% to 58%; P=.0I). The diagnosis of atrial fibrillation significantly improved in the rapid group compared wuh the standard group (median 100%, 95% C1 96% to 100% versus 95%, 95% CI 87% to 100%; P=.047) Conclusion: Correct diagnosis of narrow complex tachycardias was signihcantIy improved when ECGs at both 25 mm/s and 50 mm/s were used for interpretation h appears that the simple technique of speeding up the ECG paper, thus effectively spacing out the rhythm, enhances the diagnostic ability of the observer.
190
Comparisoflof Accuracy of Plasma Myogiobin and CK-MB for the Diagnosis of Acute Myocardial Infarction
Bassan R. Gamarski R. Volschan A, 8aspar S, Mohallem K, Macaciel R/Pr6-CardiacoHospital, Rio de Janeiro, Brazil Acute myocardial infarction (AMI) is diagnosed by ECG changes and/or elevated plasma cardiac markers. The enzymatic gold standard is creatine kinase izoenzyme MB (CK-MB), but new protein markers of myocardial injury' have been used recently. Myogtobin is a nonspecific cardiac protein that increases in AMI 1 to 3 hours after pain onset, therefore earlier than CK-MB, Study objective: To determine whether myoglobin is more accurate than CK-MB for the early diagnosis of AMI. Methods: In this prospective stud3,,, serial plasma myoglobin levels (baseline and 3, 6, and 9 hours after admission) were determined by immunoturbidimetry for the diagnosis of AMI in 688 consecutive patients with chest pain seen in the emergency department. Plasma CK-MB levels were simultaneously measured and the diagnosis of AMI was made in 156 patients by a typical CK-MB curve. Results: Median time of chest pain onset to hospital arrival was 2 0 hours for AMI patients Sensitivity of the first myoglohin determination for AMI was significantly better
OCTOBER 1999. PART 2 34:4 ANNALSOF EMERGENCYMEDICINE
than that of the first CK-MB le'.'el (69% versus 46%. P=.002), and this significant difference '...'asseen in lx~th early-arri',ang (<_2 hours) and fate-amving (>2 hours) patients. By the second measurement, the cumulative sensiti'~aties were similar. Predictive value of 2 consecutive normal myoglobin and CK-MB determinations was similar; a third normal measurement still did not rule out AMI 0 % and 1%, respectively) Conclusion: For early diagnosis of AMI, myoglobin is significantly better than CK.,MB. Better early sensiti,aty of single myogtobin determination is already seen after 1 hour of pain onset but not alter 5 hours (greater difference being with <_3 hours). Some patients `.vith AMI may still have normal myoglobin or CK MB levels at 6 hours, especially ,.,.hen they do not have ST elevation on admission
91 Physician Probability Estimatesfor Patients PresentingWith Chest Pain Schaider J, Reilly B, Das K, Roberts RR, Rydman RJ, EvansA/Cook County Hospital, Rush University. Chicago. IL The disposition of emergency department patients with chest pain is difficult and has a significant impact on the resource utilization of telemetry and critical care beds. Safely admitting patients to lower-Level care leads to improved resource allocation. Assessment of the nsk ot major complications (COMP), coronary' artery disease (CAD). and myocardial inlarction (MI) are important determinants in appropriate chest pain (CP) disposition decisions. Study objectives: The goal of this study was to determine physician estimates for the above 3 risk categories and to compare these estimates with the actual risks. Methods: Using published data, 20 CP patient cases were de`.'eloped such that each case represented a different combination of very" low low. moderate, and high risks based on COMP. CAD, and MI nsks. One hundred forty-seven physicians reviewed each case and assigned an estimate of risk (0 to 100%) for COMP. CAD. and MI for each of the 20 cases. Physician estimates were compared with the actual risks using stratified matched pair analysis Results: Forty-six emergency physicians, 88 internists, and 13 cardiologists revie`.ved ~be cases There were no significant differences between these groups. Overall, (or very- Iow-nsk CP patients, the estimated versus actual risks were: COMP 10% versus 060*,: CAD 38% versus <10%: MI 18% ".'ersus 2%. For Iow-nsk CP patients, the actual versus estimated risks were: COMP 17% versus 4%; CAD 49% versus 10% to 50~ MI 39% versus 14%. For moderate-risk CP patients, the actual versus estimated nsks were: COMP 21% versus 8%: CAD 68% versus 51% to 99%; MI 48% versus 25% For high-risk CP patients, the actual versus estimated risks were: COMP 42% versus 16%: CAD 75'}6 versus 100%; MI 82% versus 75%. Conclusion: For very Io'.v-risk CP patients, physicians overestimate the risk of COMP by a factor of 17, CAD by a factor of 7, and MI by a factor of 9. In addition, physicians overesumate complication risk for all nsk categories of patients complaining of chest pain. Better understanding of physician risk assessment should help to improve physician triage and admission decisions and to potentially improve resource allocation.
192
Serious Head Injury and Denth AssociatedWith the 0peration nf All-Terrain Vehicles and Motorcycles by Minors
Kapur RK, Mader TJ, Letourneau P/Baystate Medical Center. "ruffs University School of Medicine. Springfield, MA Study objective: In most US states, children younger than age 16 are not legally able to operate motor ;'ehicles independently. Despite this prohibition, many are allo`.ved to operate recreational vehicles (RVs). such as all-terrain vehicles (ATVs) and motorcycles (MCsJ. wathout adult supep,'ision In January, 1988, sale of new 3-wheel ATVs '.,,'ere banned in the United States because of the high incidence of senous injury associated with their use. The purpose of this study was to review the incidence of senous head irilUry and death associated wuh underage use of A W s and MCs. with and without helmet use, since ! ~88 Methods: This study was a , :rospective analysis of data collected (1988-1998) by the National Pediamc Trauma ICegistry (NPTR) for more than 75,000 pediatric trauma patients. There were 923 children in the database who were <16 years of age, injured or killed while operating an A1%' or MC and had data recorded on use of protective gear Patients who used and did not use helmets were descnptively compared. Results: The Table summarizes the main results. The grc,ups were similar in makeup All patients were admitted There was no difference in injury seventy by pediamc trauma score tPTS) bep.veen the 2 groups Of the 923 patients, 375 (41%) had neurologic complications from their injuries. Neurologic injuries accounted for
S 49