Feasibility of prehospital r-TPA therapy in chest pain patients.

STUDY OBJECTIVE: The purpose of this study was to determine the number of eligible prehospital thrombolytic candidates and to estimate the potential time saved if field thrombolysis had been initiated in a series of prehospital chest pain patients. DESIGN AND SETTING: Prehospital 12-lead ECGs were obtained by paramedics during initial evaluation of chest pain patients and stored in the computerized ECG. Prehospital 12-lead ECGs, prehospital charts, and hospital charts then were reviewed retrospectively for final hospital diagnosis, prehospital and emergency department times, and historical exclusion criteria for prehospital treatment with recombinant tissue-type plasminogen activator (r-TPA). TYPE OF PARTICIPANTS: One hundred fifty-seven stable adult prehospital patients with a chief complaint of nontraumatic chest pain were enrolled. Six patients were excluded. Two had unretrievable 12-lead ECGs, and four refused paramedic transport and thus provided no further data. There were complete data on 151 patients making up the final study population. INTERVENTIONS: Prehospital care was unaltered except for acquisition of 12-lead ECGs. No prehospital thrombolytic therapy was administered during this study. MEASUREMENTS AND MAIN RESULTS: The incidence of r-TPA exclusion criteria was as follows: 45 patients (29%) were 75 years of age or older, 57 (38%) had chest pain for more than six hours, 24 (16%) had hypertension with blood pressure of more than 180/110 mm Hg, and six (4%) had a history of a cerebrovascular accident. The time from paramedic scene arrival to prehospital ECG (8.4 +/- 5.1 minutes) was significantly shorter than the time from ED arrival to ED ECG (24.2 +/- 21.6 minutes, P less than .001). Prehospital ECGs increased paramedic scene time over a retrospective control by 5.2 minutes. Mean time from prehospital ECG to ED ECG (potential time saved) was 50.2 + 22.4 minutes in all patients and 43.4 +/- 7.7 minutes in patients with a final diagnosis of acute myocardial infarction (P = NS). Thirteen of 151 patients (8.6%) had prehospital ECGs diagnostic for acute myocardial infarction; eight of these (5.3% overall) met criteria for prehospital r-TPA therapy. CONCLUSION: Prehospital 12-lead ECGs provide an ECG diagnosis 40 to 50 minutes earlier than ED ECGs. However, with current exclusion criteria, the number of prehospital r-TPA candidates is limited.     

Milwaukee Prehospital Chest Pain Project--phase I: feasibility and accuracy of prehospital thrombolytic candidate selection.

This study prospectively determined the feasibility and accuracy of prehospital thrombolytic therapy candidate selection by base station emergency physicians. During a 6-month period, paramedics acquired and transmitted prehospital 12-lead electrocardiograms (ECGs) and then applied a thrombolytic therapy contraindication checklist. Emergency physicians interpreted prehospital ECGs and prospectively selected candidates for thrombolytic therapy. A safety committee of cardiologists reviewed prehospital ECGs, checklists and hospital records to determine accuracy independently. Six hundred-eighty stable adult prehospital patients with a chief complaint of nontraumatic chest pain were initially evaluated. Two hundred forty-one patients were excluded because of (1) unsuccessful electrocardiographic transmission (149), (2) transport to nonparticipating facilities (72), and (3) unavailable medical records (20). No prehospital thrombolytic therapy was administered in this study. Of 439 cases, 91 (21%) had the final diagnosis of acute myocardial infarction, 38 (8.7%) had diagnostic prehospital ECGs, and 12 (2.7%) were selected by emergency physicians as candidates for thrombolytic therapy. Seventy percent of patients with myocardial infarction had checklist exclusions for thrombolytic therapy. Prehospital evaluation increased mean scene time (paramedic arrival on scene to scene departure) by 4 minutes. The median time from chest pain onset to paramedic arrival in patients with myocardial infarction was 60 minutes. The estimated average time saved if prehospital thrombolytic therapy had been available was 101 +/- 81 minutes. The safety committee concluded that acceptable accuracy of emergency physician prehospital electrocardiographic interpretation, checklist and case selection was achieved. It is concluded that emergency physicians can accurately identify candidates for prehospital thrombolytic therapy.     

Evaluation of patients for the need of thrombolytic therapy in the prehospital setting

Maximum benefit from thrombolytic therapy in acute myocardial infarction is obtained with early therapy. The earliest possible time to treat is during the initial evaluation of the patient in the home or ambulance, which requires accurate diagnosis of acute myocardial infarction in the prehospital setting. In our study, paramedics evaluated patients who had chest pain with a 12-lead ECG transmitted by cellular telephone and a checklist for inclusion and exclusion criteria for thrombolytic therapy. This information was transmitted to a hospital-based telemetry physician who diagnosed or excluded acute myocardial infarction and made a mock decision to withhold or administer a thrombolytic agent. Forty-eight patients with chest pain were evaluated. Six were diagnosed as having overt acute myocardial infarction by the hospital-based telemetry physician. All six patients had the diagnosis substantiated by both ECG and enzyme studies on hospital admission. Based on the data supplied by paramedics, two of these six patients were considered eligible for thrombolytic therapy by the physician. Hospital evaluation confirmed the prehospital decision to treat with a thrombolytic agent. In addition, all other patients were appropriately diagnosed as ineligible. Prehospital ECG diagnosis resulted in two patients going directly to the catheterization lab, thereby bypassing the emergency department. Overt acute myocardial infarction can be accurately identified by a prehospital-acquired 12-lead ECG transmitted to a hospital-based physician. Our study demonstrates that in conjunction with specially trained paramedics, the hospital physician can decide whether to administer thrombolytic therapy to such patients in the prehospital setting.     

Cellular telephone transmission of 12-lead electrocardiograms from ambulance to hospital

Currently, only single-lead, serial telemetry rhythm strips can be transmitted from ambulances. Triage of patients with chest pain and administration of thrombolytic therapy in ambulances is limited by the lack of specific electrocardiographic (ECG) diagnosis. A new technique is described using cellular telephone transmission of simultaneous 12-lead ECGs from ambulance to hospital to overcome this limitation. A portable 12-lead ECG installed in an ambulance was connected via modern link to a cellular telephone and digitized ECG information was transmitted to an ECG device in the hospital emergency room. Paramedics in the field placed adhesive patch electrodes and attached ECG wires. Field ECGs from 23 patients were compared with corresponding transmitted ECGs. There were no differences in heart rate, PR interval, QRS duration, QT interval or R- and T-wave axes. Baseline and transmitted ECGs had identical morphologic characteristics. Differences in R-wave amplitude in 5 transmitted tracings compared with hospital-recorded ECGs resulted in computer diagnosis of left ventricular hypertrophy by voltage, possibly due to differences in patient position. Twelve-lead ECGs can be easily transmitted from a moving ambulance using cellular telephones. This allows diagnosis before hospital arrival, improves prehospital triage of patients and may facilitate prehospital therapy with lidocaine or streptokinase. In addition, the cellular telephone link can convey both verbal and digitized information and thus improve on current telemetry systems.     

Utility of the prehospital electrocardiogram in diagnosing acute coronary syndromes: the Myocardial Infarction Triage and Intervention (MITI) project

Objectives. We sought to determine whether the prehospital electrocardiogram (ECG) improves the diagnosis of an acute coronary syndrome.Background. The ECG is the most widely used screening test for evaluating patients with chest pain.Methods. Prehospital and in-hospital ECGs were obtained in 3,027 consecutive patients with symptoms of suspected acute myocardial infarction, 362 of whom were randomized to prehospital versus hospital thrombolysis and 2,665 of whom did not participate in the randomized trial. Prehospital and hospital records were abstracted for clinical characteristics and diagnostic outcome.Results. ST segment and T and Q wave abnormalities suggestive of myocardial ischemia or infarction were more common on both the prehospital and hospital ECGs of patients with as compared with those without acute coronary syndromes (p ≤ 0.00001). Those with prehospital thrombolysis were more likely to show resolution of ST segment elevation by the time of hospital admission (14% vs. 5% in patients treated in the hospital, p = 0.004). In patients not considered for prehospital thrombolysis, both persistent and transient ST segment and T or Q wave abnormalities discriminated those with from those without acute coronary ischemia or infarction. Compared with ST segment elevation on a single ECG, added consideration of dynamic changes in ST segment elevation between serial ECGs improved the sensitivity for an acute coronary syndrome from 34% to 46% and reduced specificity from 96% to 93% (both p < 0.00004). Overall, compared with abnormalities observed on a single ECG, consideration of serial evolution in ST segment, T or Q wave or left bundle branch block (LBBB) abnormalities between the prehospital and initial hospital ECG improved the diagnostic sensitivity for an acute coronary syndrome from 80% to 87%, with a fall in specificity from 60% to 50% (both p < 0.000006).Conclusions. ECG abnormalities are an early manifestation of acute coronary syndromes and can be identified by the prehospital ECG. Compared with a single ECG, the additional effect of evolving ST segment, T or Q waves or LBBB between serially obtained prehospital and hospital ECGs enhanced the diagnosis of acute coronary syndromes, but with a fall in specificity.     

A simple strategy improves prehospital electrocardiogram utilization and hospital treatment for patients with acute coronary syndrome (from the ST SMART Study)

Although the American Heart Association recommends a prehospital electrocardiogram (ECG) be recorded for all patients who access the emergency medical system with symptoms of acute coronary syndrome (ACS), widespread use of prehospital ECG has not been achieved in the United States. A 5-year prospective randomized clinical trial was conducted in a predominately rural county in northern California to test a simple strategy for acquiring and transmitting prehospital ECGs that involved minimal paramedic training and decision making. A 12-lead ECG was synthesized from 5 electrodes and continuous ST-segment monitoring was performed with ST-event ECGs automatically transmitted to the destination hospital emergency department. Patients randomized to the experimental group had their ECGs printed out in the emergency department with an audible voice alarm, whereas control patients had an ECG after hospital arrival, as was the standard of care in the county. The result was that nearly 3/4 (74%) of 4,219 patients with symptoms of ACS over the 4-year study enrollment period had a prehospital ECG. Mean time from 911 call to first ECG was 20 minutes in those with a prehospital ECG versus 79 minutes in those without a prehospital ECG (p <0.0001). Mean paramedic scene time in patients with a prehospital ECG was just 2 minutes longer than in those without a prehospital ECG (95% confidence interval 1.2 to 3.6, p <0.001). Patients with non-ST-elevation myocardial infarction or unstable angina pectoris had a faster time to first intravenous drug and there was a suggested trend for a faster door-to-balloon time and lower risk of mortality in patients with ST-elevation myocardial infarction. In conclusion, increased paramedic use of prehospital ECGs and decreased hospital treatment times for ACS are feasible with a simple approach tailored to characteristics of a local geographic region.     

Comparison of EASI-derived 12-lead electrocardiograms versus paramedic-acquired 12-lead electrocardiograms using Mason-Likar limb lead configuration in patients with chest pain

INTRODUCTION: Monitoring or serial 12-lead electrocardiogram (ECG) recordings are the accepted requirement for prehospital data acquisition in patients with chest pain. The purpose of this study was to determine whether waveforms and clinical triage decision are similar in EASI-derived ECGs and paramedic-acquired 12-lead ECGs using Mason-Likar limb lead configuration when compared with standard 12-lead ECGs (stdECG). METHOD: Twenty patients with chest pain had a prehospital 12-lead ECG recorded in the ambulance, and paramedic-applied electrodes retained in place at hospital arrival. An ECG technician applied standard precordial and EASI electrodes in their correct positions. Twelve-lead ECGs were obtained from the paramedic-applied electrodes, using their Mason-Likar limb lead configuration, and derived from the EASI leads for comparison with the stdECG. Three computer-measured QRS-T waveform parameters were considered, and differences in waveform measurement between EASI and stdECG (EASIDeltastdECG) versus differences in waveform measurements between paramedic Mason-Likar and stdECG (PMLDeltastdECG) were calculated. Two physicians determined whether the EASI-derived or the paramedic Mason-Likar ECG contained information that would change their clinical triage decision from that indicated by the stdECG. RESULTS: EASIDeltastdECG and PMLDeltastdECG were identical in 28%, whereas EASIDeltastdECG was more than PMLDeltastdECG in 35%, and PMLDeltastdECG was accurate (both time) than EASIDeltastdECG in 37% (P = .62). The physicians were more likely to change the level of patient care based on the EASI-derived ECGs compared with the paramedic ECGs; however, this difference was not statistically significant (P = .27), but this may only be caused by the small study population. CONCLUSIONS: There are similar differences from stdECG waveforms in EASI-derived ECGs and those acquired via paramedic-applied precordial electrodes using Mason-Likar limb lead configuration. Either method can be used as a substitute for monitoring, but neither should be considered equivalent to the stdECG for diagnostic purposes.     

Myocardial Infarction Triage and Intervention Project--phase I: patient characteristics and feasibility of prehospital initiation of thrombolytic therapy

Prehospital initiation of thrombolytic therapy by paramedics, if both feasible and safe, could considerably reduce the time to treatment and possibly decrease the extent of myocardial necrosis in patients with acute coronary thrombosis. Preliminary to a trial of such a treatment strategy, paramedics evaluated the characteristics of 2,472 patients with chest pain of presumed cardiac origin; 677 (27%) had suitable clinical findings consistent with possible acute myocardial infarction and no apparent risk of complication for potential thrombolytic drug treatment. Electrocardiograms (ECGs) of 522 of the 677 patients were transmitted by cellular telephone to a base station physician; 107 (21%) of the tracings showed evidence of ST segment elevation. Of the total 2,472 patients, 453 developed evidence of acute myocardial infarction in the hospital; 163 (36%) of the 453 had met the strict prehospital screening history and examination criteria and 105 (23.9%) showed ST elevation on the ECG and, thus, would have been suitable candidates for prehospital thrombolytic treatment if it had been available. The average time from the onset of chest pain to prehospital diagnosis was 72 +/- 52 min (median 52); this was 73 +/- 44 min (median 62) earlier than the time when thrombolytic treatment was later started in the hospital. Paramedic selection of appropriate patients for potential prehospital initiation of thrombolytic treatment is feasible with use of a directed checklist and cellular-transmitted ECG and saves time. This strategy may reduce the extent and complications of infarction compared with results that can be achieved in a hospital setting.     

Accuracy of computer-interpreted electrocardiography in selecting patients for thrombolytic therapy. MITI Project Investigators

A prehospital computer-interpreted electrocardiogram (ECG) was obtained in 1,189 patients with chest pain of suspected cardiac origin during an ongoing trial of prehospital thrombolytic therapy in acute myocardial infarction. Electrocardiograms were performed by paramedics 1.5 +/- 1.2 h after the onset of symptoms. Of 391 patients with evidence of acute myocardial infarction, 202 (52%) were identified as having ST segment elevation (acute injury) by the computer-interpreted ECG compared with 259 (66%) by an electrocardiographer (p less than 0.001). Of 798 patients with chest pain but no infarction, 785 (98%) were appropriately excluded by computer compared with 757 (95%) by an electrocardiographer (p less than 0.001). The positive predictive value of the computer- and physician-interpreted ECG was, respectively, 94% and 86% and the negative predictive value was 81% and 85%. Prehospital screening of possible candidates for thrombolytic therapy with the aid of a computerized ECG is feasible, highly specific and with further enhancement can speed the care of all patients with acute myocardial infarction.     

Limitations of prehospital predictors of acute myocardial infarction and unstable angina

Studies have attempted to define predictive indicators of diagnosis and/or prognosis for acute myocardial infarction (AMI) in the emergency department and to identify the need for hospital admission in patients with chest pain. Because prehospital predictors have not been defined, dispatchers, paramedics, and base station physicians continue to triage based on patient history. We reviewed 401 patients presenting in one year to an urban paramedic system with chest pain, normal vital signs, and stable rhythms to identify predictors of AMI and unstable angina. Thirty-one percent (123) had a diagnosis of AMI, 26% (105) unstable angina, and 43% (173) "other" diagnoses. Two-hundred seventy-eight patients required nitroglycerin administration, 182 required IV morphine, 14 developed arrhythmias requiring lidocaine, and two suffered cardiac arrest in the field. Nine other patients had a cardiac arrest after arrival in the ED. When comparing AMI and unstable angina patients to the "others," 64% (132) versus 36% (74) had radiation of pain (P less than .003), 72% (95) versus 28% (37) had diaphoresis (P less than .0001). Neither difficulty breathing, nausea/vomiting, vital signs, initial rhythm, nor past history of myocardial infarction were helpful in discriminating AMI and unstable angina from others. Comparing AMI alone versus others, the presence of ST segment elevation on lead II was present in 15% (18) AMIs, 3% (3) unstable angina, and 8% (14) others (P = .005). Diaphoresis also was a predictor of diagnosis with 51% (63) of the AMIs and 25% (69) of others exhibiting this sign (P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)     

ST depression only on the initial 12-lead ECG: early diagnosis of acute myocardial infarction.

AIMS: To compare the diagnostic ability of the 12-lead ECG with body surface mapping for early detection of acute myocardial infarction in patients presenting with ST depression only on the 12-lead ECG. METHODS AND RESULTS: Fifty-four consecutive patients with chest pain <24 h and ST depression were recruited. A 12-lead ECG and 80-lead body surface map were recorded at presentation from which univariate and multivariate prediction models of acute myocardial infarction were developed. Patients were randomly divided into a training-set and a validation-set. Acute myocardial infarction occurred in 16/30 training-set and 8/24 validation-set patients. Univariate prediction of acute myocardial infarction by the 12-lead ECG, based on the depth or numbers of leads with ST depression, was not improved by assessment of ST elevation outside the conventional 12 leads using body surface mapping. The optimum multivariate 12-lead ECG model developed in training-set patients (six ST depression variables) had poor sensitivity (38%) although good specificity (81%) for acute myocardial infarction when tested prospectively in validation-set patients. In contrast, the optimum body surface mapping model developed in training-set patients (three isointegral or isopotential variables) achieved high sensitivity (88%) whilst maintaining good specificity (75%) for acute myocardial infarction when tested prospectively in validation-set patients. CONCLUSION: Body surface mapping, when compared with the 12-lead ECG, may improve the early diagnosis of acute myocardial infarction in patients presenting with chest pain and ST depression only on the 12-lead ECG.     

Clinical policy: critical issues in the evaluation and management of adult patients presenting with suspected acute myocardial infarction or unstable angina. American College of Emergency Physicians

This clinical policy focuses on critical issues in the evaluation and management of patients with acute myocardial infarction or unstable angina. A MEDLINE search for articles published between January 1993 and December 1998 was performed using combinations of the key words chest pain, acute myocardial infarction, unstable angina, thrombolytics, primary angioplasty, 12-lead ECG, ST-segment monitoring, cardiac serum markers, and chest pain centers. Subcommittee members and expert peer reviewers also supplied articles with direct bearing on the policy. This policy focuses on 5 areas of current interest and/or controversy: (1) ECG eligibility criteria for fibrinolytic therapy, (2) role of primary angioplasty in patients with acute myocardial infarction, (3) use of serum markers to diagnose acute myocardial infarction, (4) serial 12-lead ECGs during the initial evaluation, and (5) chest pain evaluation units. Recommendations for patient management are provided for each of these 5 topics based on strength of evidence (Standards, Guidelines, Options). Standards represent patient management principles that reflect a high degree of clinical certainty; Guidelines represent patient management principles that reflect moderate clinical certainty; and Options represent other patient management strategies based on preliminary, inconclusive, or conflicting evidence, or based on panel consensus. This guideline is intended for physicians working in hospital-based emergency departments or chest pain evaluation units.     

The effect of telemetry on urban prehospital cardiac care

A three-year, controlled trial of the use of telemetry in the prehospital care of cardiac patients was conducted in a major metropolitan area. Five of the ten paramedic squads in the city used telemetry; the other five squads did not. We studied the effect of telemetry on the following: paramedics' abilities to recognize ECGs in a written test; paramedics' abilities to identify ECG arrhythmias in the field; length of time spent by paramedics in the field; survival rates of patients with ventricular fibrillation (VF) cared for by paramedics; abilities of base station physicians to interpret telemetered ECGs; and attitudes of paramedics toward using telemetry. Telemetry was not found to affect the abilities of paramedics to read ECGs in either test or field situations. Paramedics who used telemetry spent more time in the field with their patients than did paramedics who did not use telemetry (P less than .02). We found no statistically significant effect of telemetry on survival rates of VF patients. Using matched ECGs, readings by base station physicians were found to be more accurate than were those by paramedics (P less than .01). Paramedics overwhelmingly reported that telemetry did not help them to save patients' lives, but that it did help them to treat patients with certain arrhythmias. The results suggest that telemetry may not improve either paramedics' abilities to identify arrhythmias or prehospital care for all cardiac patients. The implications for emergency services researchers are discussed.     

Accuracy of 22-lead ECG analysis for diagnosis of acute myocardial infarction and coronary artery disease in the emergency department: a comparison with 12-lead ECG.

STUDY OBJECTIVES: To compare a new 22-lead ECG with the 12-lead ECG for diagnosis of acute myocardial infarction (AMI). DESIGN: Prospective study of all consenting patients presenting to the emergency department with chest pain. SETTING: Urban hospital ED. TYPE OF PARTICIPANTS: 163 patients admitted with a cardiac-related diagnosis and complete data sets of 22- and 12-lead ECG results and creatine kinase-MB analysis. INTERVENTIONS: Patient care and existing protocols were unaltered, with the exception of including the new 22-lead ECG. MEASUREMENTS AND MAIN RESULTS: Forty-one of 163 patients had an AMI as defined by creatine kinase-MB analysis. The 22-lead ECG provided a statistically significant improvement in sensitivity (83%) for AMI diagnosis over the 12-lead ECG (51%) with specificities of 76% and 99%, respectively. CONCLUSION: When combined with clinical judgment, the 22-lead ECG could provide a 97.6% sensitivity for AMI diagnosis while reducing unnecessary admissions for "rule-out MI" by 69%.     

Effect on treatment delay of prehospital teletransmission of 12-lead electrocardiogram to a cardiologist for immediate triage and direct referral of patients with ST-segment elevation acute myocardial infarction to primary percutaneous coronary intervention

Prehospital electrocardiogram (ECG) transmission to hospitals was shown to reduce time to treatment in patients with acute myocardial infarction. However, new technologies allow transmission directly to a mobile unit so an attending physician can respond irrespective of presence within or outside the hospital. The primary study purpose was to determine whether delays could be decreased in an urban area by transmitting a prehospital 12-lead ECG directly to the attending cardiologist's mobile telephone for rapid triage and transport to a primary percutaneous coronary intervention (PCI) center, bypassing local hospitals and emergency departments. A secondary purpose was to describe whether transport would be safe despite longer transport times. During a 2-year period, patients with acute nontraumatic chest pain had their prehospital ECG transmitted directly to a cardiologist's mobile telephone. Time to treatment was compared with historic controls. After ECG evaluation, 168 patients (30%) were referred directly for PCI, and 146 of these (87%) underwent emergent catheterization. In referred patients, median time from 911 call to PCI was significantly shorter than in the control group (74 vs 127 minutes; p <0.001). Accordingly, door-to-PCI time was 63 minutes shorter for referred patients versus controls (34 vs 97 minutes; p <0.001). During transport, 7 patients (4%) experienced ventricular fibrillation; 3 patients (2%), ventricular tachycardia; and 1 patient (0.5%), pulseless electrical activity, including 2 deaths (1%) caused by treatment-resistant arrhythmia. In conclusion, transmission of a prehospital 12-lead ECG directly to the attending cardiologist's mobile telephone decreased door-to-PCI time by >1 hour when patients were transported directly to PCI centers, bypassing local hospitals. Ambulance transport seems safe despite longer transport times.     

Prehospital troponin T testing in the diagnosis and triage of patients with suspected acute myocardial infarction

Prehospital electrocardiographic (ECG) diagnosis has improved triage and outcome in patients with acute ST-elevation myocardial infarction. However, many patients with acute myocardial infarction (AMI) present with equivocal ECG patterns making prehospital ECG diagnosis difficult. We aimed to investigate the feasibility and ability of prehospital troponin T (TnT) testing to improve diagnosis in patients with chest pain transported by ambulance. From June 2008 through September 2009, patients from the central Denmark region with suspected AMI and transported by ambulance were eligible for prehospital TnT testing with a qualitative point-of-care test (cutpoint 0.10 ng/ml). Quantitative TnT was measured at hospital arrival and after 8 and 24 hours (cutpoint 0.03 ng/ml). A prehospital electrocardiogram was recorded in all patients. Prehospital TnT testing was attempted in 958 patients with a 97% success rate. In 258 patients, in-hospital TnT values were increased (≥0.03 ng/ml) during admission. The prehospital test identified 26% and the first in-hospital test detected 81% of patients with increased TnT measurements during admission. A diagnosis of AMI was established in 208 of 258 patients with increased TnT. The prehospital test identified 30% of these patients, whereas the first in-hospital test detected 79%. Median times from symptom onset to blood sampling were 83 minutes (46 to 167) for the prehospital sample and 165 minutes (110 to 276) for the admission sample. In conclusion, prehospital TnT testing is feasible with a high success rate. This study indicates that prehospital implementation of quantitative tests, with lower detection limits, could identify most patients with AMI irrespective of ECG changes.     

院前心电图对ST段抬高型心肌梗死患者进门至再灌注时间的影响

目的观察院前12导联心电图对急性ST段抬高心肌梗死(STEMI)患者进门至再灌注时间的影响。方法多中心现况调查2006年1～12月期间就诊于北京市19所医院并接受再灌注治疗的急性STEMI患者。根据有无院前心电图分为有心电图组和无心电图组。结果 635例患者中,接受直接经皮冠脉介入治疗(PPCI)者506例(79.7%),其中有心电图者211例(41.7%),无心电图者295例(58.3%);接受溶栓者129例(20.3%),其中有心电图者46例(35.7%),无心电图者83例(64.3%)。院前心电图可显著缩短进门-球囊扩张时间(中位数,120 min比150 min;P0.01),而对进门-溶栓时间(中位数,74min比93min;P=0.168)无影响。有心电图组进门90min内完成球囊扩张的比例显著高于无心电图组(24.6%比15.9%,P=0.017)。无论接受何种再灌注治疗,院前心电图对住院病死率无影响。结论院前心电图可显著缩短STEMI患者的进门-球囊扩张时间。应进一步提高院前心电图完成率。     

Right precordial and posterior electrocardiographic leads do not increase detection of ischemia in low-risk patients presenting with chest pain

BACKGROUND: A number of innovative approaches have been investigated for their value in the early detection of acute ischemia or infarction in patients presenting to the emergency department (ED) with chest pain suggestive of a cardiac origin. Prior investigations have demonstrated the utility of adding right precordial and posterior chest leads to the standard 12-lead electrocardiogram (ECG) for identifying right ventricular and posterior wall infarctions in the ED. HYPOTHESIS: To assess the utility of additional ECG leads in low-risk patients presenting to the ED with symptoms suggestive of acute coronary syndromes who are managed in a chest pain evaluation unit (CPEU). METHODS: We studied low-risk patients who presented to the ED with chest pain compatible with myocardial ischemia. Low-risk patients were identified by a normal 12-lead ECG, no arrhythmias or hemodynamic instability, and one negative serum cardiac troponin I. Patients were admitted to the CPEU where a 16-lead ECG was recorded by the addition of 2 right-sided precordial leads (V4R, V5R) and 2 posterior leads (V8, V9) to the standard 12-lead ECG. RESULTS: The 16-lead ECG system was applied to 316 consecutive patients. The study group was a middle-aged population with equal numbers of men and women and an average of 2 cardiac risk factors per patient. The 16-lead ECG demonstrated evidence of myocardial injury in only 1 patient and no evidence of ischemia in any of the 316 patients. CONCLUSION: In patients presenting to the ED with chest pain and evidence of low clinical risk by our criteria, the addition of both right-sided precordial and posterior chest leads to the standard 12-lead ECG did not provide additional information for risk stratification.     

The Prehospital Electrocardiogram in Acute Myocardial Infarction: Is Its Full Potential Being Realized?

Objectives. This study sought to examine the management and subsequent outcomes of patients with a prehospital electrocardiogram (ECG) in a large, voluntary registry of myocardial infarction.Background. The prehospital ECG has been proposed as a means of rapidly identifying patients with acute myocardial infarction who might be eligible for reperfusion therapy.Methods. The characteristics and outcomes of patients with a prehospital ECG were compared with those without a prehospital ECG in the National Registry of Myocardial Infarction 2 data base. Included in the analysis were those patients who presented to the hospital within 12 h of an acute myocardial infarction. Excluded were patients with an in-hospital infarction, transferred-in referrals and self-transported patients.Results. Prehospital ECGs were obtained in 3,768 (5%) of 66,995 National Registry of Myocardial Infarction 2 patients meeting study criteria. Median time from myocardial infarction symptom onset until hospital arrival was longer among those having a prehospital ECG (152 vs. 91 min, p < 0.001). However, once in the hospital, the prehospital ECG group experienced a shorter median time to the initiation of either thrombolysis (30 vs. 40 min, p < 0.001) or primary angioplasty (92 vs. 115 min, p < 0.001). The prehospital ECG group was more likely to receive thrombolytic therapy (43% vs. 37%, p < 0.001) and to undergo primary angioplasty (11% vs. 7%, p < 0.001). Also, the prehospital ECG group was more likely to undergo coronary arteriography (55% vs. 40%, p < 0.001), angioplasty (24% vs. 16%, p < 0.001) or bypass surgery (10% vs. 6%, p < 0.001). The in-hospital mortality rate was 8% in patients with a prehospital ECG and 12% in those without a prehospital ECG (p < 0.001). After adjusting for baseline covariates utilizing multiple logistic regression analysis, this mortality difference remained statistically significant (odds ratio 0.83, 95% confidence interval 0.71 to 0.96, p = 0.01).Conclusions. The prehospital ECG is infrequently utilized for diagnosing myocardial infarction, and among patients with a prehospital ECG, is associated with a longer time from symptom onset to hospital arrival. Despite these shortcomings, the prehospital ECG is a test that may potentially influence the management of patients with acute myocardial infarction through wider, faster in-hospital utilization of reperfusion strategies and greater usage of invasive procedures, factors that may possibly reduce short-term mortality. Efforts to implement the prehospital ECG more widely and more rapidly may be indicated.(J Am Coll Cardiol 1997;29:498–505)     

Prehospital 12-lead ST-segment monitoring improves the early diagnosis of acute coronary syndrome

Aims/MethodsWe studied 620 patients who activated “911” for chest pain symptoms to determine the sensitivity and specificity of 12-lead electrocardiogram (ECG) ST-segment monitoring in the prehospital period (PH ECG) for diagnosing acute coronary syndrome (ACS) and to assess whether the addition of PH ECG signs of ischemia/injury to the initial hospital 12-lead ECG obtained in the emergency department would improve the diagnosis of ACS.ResultsThe sensitivity and specificity of the PH ECG were 65.4% and 66.4%. There was a significant increase in sensitivity (79.9%) and decrease in specificity (61.2%) when considered in conjunction with the initial hospital ECG (P < .001). Those with PH ECG ischemia/injury were more than 2.5 times likely to have an ACS diagnosis than those who had no PH ECG ischemia/injury (P < .001).ConclusionsPrehospital ECG data obtained with 12-lead ST-segment monitoring provides diagnostic information about ACS above and beyond the initial hospital ECG.