Accuracy and clinical effect of out-of-hospital electrocardiography in the diagnosis of acute cardiac ischemia: a meta-analysis

Machine learning for ECG diagnosis and risk stratification of occlusion myocardial infarction

Patients with occlusion myocardial infarction (OMI) and no ST-elevation on presenting electrocardiogram (ECG) are increasing in numbers. These patients have a poor prognosis and would benefit from immediate reperfusion therapy, but, currently, there are no accurate tools to identify them during initial triage. Here we report, to our knowledge, the first observational cohort study to develop machine learning models for the ECG diagnosis of OMI. Using 7,313 consecutive patients from multiple clinical sites, we derived and externally validated an intelligent model that outperformed practicing clinicians and other widely used commercial interpretation systems, substantially boosting both precision and sensitivity. Our derived OMI risk score provided enhanced rule-in and rule-out accuracy relevant to routine care, and, when combined with the clinical judgment of trained emergency personnel, it helped correctly reclassify one in three patients with chest pain. ECG features driving our models were validated by clinical experts, providing plausible mechanistic links to myocardial injury.

Machine Learning for the ECG Diagnosis and Risk Stratification of Occlusion Myocardial Infarction at First Medical Contact

Patients with occlusion myocardial infarction (OMI) and no ST-elevation on presenting ECG are increasing in numbers. These patients have a poor prognosis and would benefit from immediate reperfusion therapy, but we currently have no accurate tools to identify them during initial triage. Herein, we report the first observational cohort study to develop machine learning models for the ECG diagnosis of OMI. Using 7,313 consecutive patients from multiple clinical sites, we derived and externally validated an intelligent model that outperformed practicing clinicians and other widely used commercial interpretation systems, significantly boosting both precision and sensitivity. Our derived OMI risk score provided superior rule-in and rule-out accuracy compared to routine care, and when combined with the clinical judgment of trained emergency personnel, this score helped correctly reclassify one in three patients with chest pain. ECG features driving our models were validated by clinical experts, providing plausible mechanistic links to myocardial injury.

Identification of Coronary Culprit Lesion in ST Elevation Myocardial Infarction by Using Deep Learning

OBJECTIVE

Early revascularization of the occluded coronary artery in patients with ST elevation myocardial infarction (STEMI) has been demonstrated to decrease mortality and morbidity. Currently, physicians rely on features of electrocardiograms (ECGs) to identify the most likely location of coronary arteries related to an infarct. We sought to predict these culprit arteries more accurately by using deep learning.

METHODS

A deep learning model with a convolutional neural network (CNN) that incorporated ECG signals was trained on 384 patients with STEMI who underwent primary percutaneous coronary intervention (PCI) at a medical center. The performances of various signal preprocessing methods (short-time Fourier transform [STFT] and continuous wavelet transform [CWT]) with different lengths of input ECG signals were compared. The sensitivity and specificity for predicting each infarct-related artery and the overall accuracy were evaluated.

RESULTS

ECG signal preprocessing with STFT achieved fair overall prediction accuracy (79.3%). The sensitivity and specificity for predicting the left anterior descending artery (LAD) as the culprit vessel were 85.7% and 88.4%, respectively. The sensitivity and specificity for predicting the left circumflex artery (LCX) were 37% and 99%, respectively, and the sensitivity and specificity for predicting the right coronary artery (RCA) were 88.4% and 82.4%, respectively. Using CWT (Morlet wavelet) for signal preprocessing resulted in better overall accuracy (83.7%) compared with STFT preprocessing. The sensitivity and specificity were 93.46% and 80.39% for LAD, 56% and 99.7% for LCX, and 85.9% and 92.9% for RCA, respectively.

CONCLUSION

Our study demonstrated that deep learning with a CNN could facilitate the identification of the culprit coronary artery in patients with STEMI. Preprocessing ECG signals with CWT was demonstrated to be superior to doing so with STFT.

Changes in High-Frequency Intracardiac Electrogram Indicate Cardiac Ischemia

High-frequency QRS (HFQRS) analysis of surface ECG is a reliable marker of cardiac ischemia (CI). This study aimed to assess the response of HFQRS signals from standard intracardiac electrodes (iHFQRS) to CI in swine and compare them with conventional ST-segment deviations. Devices with three intracardiac leads were implanted in three swine in a controlled environment. CI was induced by inflating a balloon in epicardial coronary arteries. A designated signal-processing algorithm was applied to quantify the iHFQRS content before, during, and after each occlusion. iHFQRS time responses were compared to conventional ST-segment deviations. Thirty-three over thirty-nine (85%) of the occlusions presented significant reduction in the iHFQRS signal, preceding ST-segment change, being the only indicator of CI in brief occlusions. iHFQRS was found to be an early indicator for the onset of CI and demonstrated superior sensitivity to conventional ST-segment deviations during brief ischemic episodes.

Low diagnostic yield of ST elevation myocardial infarction amplitude criteria in chest pain patients at the emergency department

OBJECTIVES

To evaluate the diagnostic yield of the ECG criteria for ST-elevation myocardial infarction in a large cohort of emergency department chest pain patients, and to determine whether extended ECG criteria or reciprocal ST depression can improve accuracy. Design: Observational, register-based diagnostic study on the accuracy of ECG criteria for ST-elevation myocardial infarction. Between Jan 2010 and Dec 2014 all patients aged ≥30 years with chest pain who had an ECG recorded within 4 h at two emergency departments in Sweden were included. Exclusion criteria were: ECG with poor technical quality; QRS duration ≥120 ms; ECG signs of left ventricular hypertrophy; or previous coronary artery bypass surgery. Conventional and extended ECG criteria were applied to all patients. The main outcome was acute myocardial infarction (AMI) and an occluded/near-occluded coronary artery at angiography. Results: Finally, 19932 patients were included. Conventional ECG criteria for ST elevation myocardial infarction were fulfilled in 502 patients, and extended criteria in 1249 patients. Sensitivity for conventional ECG criteria in diagnosing AMI with coronary occlusion/near-occlusion was 17%, specificity 98% and positive predictive value 12%. Corresponding data for extended ECG criteria were 30%, 94% and 8%. When reciprocal ST depression was added to the criteria, the positive predictive value rose to 24% for the conventional and 23% for the extended criteria. Conclusions: In unselected chest pain patients at the emergency department, the diagnostic yield of both conventional and extended ECG criteria for ST-elevation myocardial infarction is low. The PPV can be increased by also considering reciprocal ST depression.

Systematic Review of Clinical Decision Support Systems for Prehospital Acute Coronary Syndrome Identification

OBJECTIVES

Timely prehospital diagnosis and treatment of acute coronary syndrome (ACS) are required to achieve optimal outcomes. Clinical decision support systems (CDSS) are platforms designed to integrate multiple data and can aid with management decisions in the prehospital environment. The review aim was to describe the accuracy of CDSS and individual components in the prehospital ACS management.

METHODS

This systematic review examined the current literature regarding the accuracy of CDSS for ACS in the prehospital setting, the influence of computer-aided decision-making and of 4 components: electrocardiogram, biomarkers, patient history, and examination findings. The impact of these components on sensitivity, specificity, and positive and negative predictive values was assessed.

RESULTS

A total of 11,439 articles were identified from a search of databases, of which 199 were screened against the eligibility criteria. Eight studies were found to meet the eligibility and quality criteria. There was marked heterogeneity between studies which precluded formal meta-analysis. However, individual components analysis found that patient history led to significant improvement in the sensitivity and negative predictive values. CDSS which incorporated all 4 components tended to show higher sensitivities and negative predictive values. CDSS incorporating computer-aided electrocardiogram diagnosis showed higher specificities and positive predictive values.

CONCLUSIONS

Although heterogeneity precluded meta-analysis, this review emphasizes the potential of ACS CDSS in prehospital environments that incorporate patient history in addition to integration of multiple components. The higher sensitivity of certain components, along with higher specificity of computer-aided decision-making, highlights the opportunity for developing an integrated algorithm with computer-aided decision support.

Review article: Impact of 12-lead electrocardiography system of care on emergency medical service delays in ST-elevation myocardial infarction: A systematic review and meta-analysis

To assess the impact of prehospital 12-lead electrocardiography (PH ECG) on emergency medical service (EMS) delay in patients with ST-elevation myocardial infarction (STEMI), we systematically searched five online electronic databases, including MEDLINE, Embase, Emcare, Cochrane Library and CINAHL, between 1990 and August 2017. Controlled trials and observational studies comparing EMS time delays with and without PH ECG in STEMI patients were eligible. Two reviewers independently screened studies for eligibility, extracted data and appraised study quality. The primary outcome was the time elapsed between scene arrival and hospital arrival. The secondary outcomes were response time, scene time, transport time and emergency call-to-hospital arrival time. Random effects models were used to pool weighted mean differences in EMS delay. Seven moderate-quality studies (two controlled trials and five observational) involving 81 005 participants were included in the data synthesis. The primary treatment strategy was in-hospital thrombolysis and percutaneous coronary intervention in four and three studies, respectively. PH ECG was associated with a 7.0 min increase in scene arrival-to-hospital arrival time (three studies; n = 80 628; 95% CI 6.7-7.2; I² = 0.0%) and a 2.9 min increase in scene time (four studies; n = 377; 95% CI 1.2-4.6; I² = 0.0%). PH ECG had no effect on transport or call-to-hospital intervals, although both measures showed evidence of heterogeneity. In patients with STEMI, PH ECG is associated with a modest increase in EMS delays. Measurement and improvement of EMS system delays may help to expedite treatment for STEMI.

The conundrum of acute chest pain in general practice: a nationwide survey in The Netherlands

Background

GPs are frequently confronted with patients with acute onset chest pain. Although usually benign, approximately 5% is due to acute coronary syndrome (ACS). Unfortunately, ACS is not always recognised, leading to a missed diagnosis in 2–5% of presentations.

Aim

The authors set out to study the level of risk GPs are willing to accept with regards to missing an ACS diagnosis, and the receptiveness of implementing new clinical decision aids.

Design & setting

This study involved an online survey among GPs in the Netherlands.

Method

A concept survey was constructed, which was tested among a panel of 24 GPs. The survey was then modified to achieve content validity. This survey was electronically distributed among 1000 GPs.

Results

A total of 313 (31.3%) GPs completed the survey. Of those surveyed, the median age was 50 years (interquartile range 41–57), 53.0% were female, and 6.4% were specialist GPs ('kaderarts') in cardiology or acute care. GPs estimated the missed ACS rate to be <5.0% in clinical practice, most often estimating a chance of 1.0–2.5% (35.2%) or 0.5–1.0% (29.7%). For atypical case presentations, 70% of GPs would accept a 0.1–1.0% missed diagnosis rate, while keeping the referral threshold to a maximum of 50 unnecessary referrals for each ACS case (75% of responders). GPs would welcome additional decision aids, with 79.2% favouring a clinical decision aid, 77.1% favouring troponin point-of-care (POC) testing, and 85.5% favoring a combination of a clinical decision aid and a troponin POC test.

Conclusion

GPs perceive that they miss more ACS cases than they feel comfortable with, which is reflected in a defensive referral strategy. The vast majority of GPs would welcome the use of clinical decision aids and/or cardiac biomarker POC testing for ruling out ACS, if accompanied by more certainty than based on clinical judgment alone.

Pre-hospital detection of acute ischemic stroke secondary to emergent large vessel occlusion: lessons learned from electrocardiogram and acute myocardial infarction

Currently, there is no device capable of detecting acute ischemic stroke (AIS) secondary to emergent large vessel occlusion (ELVO) in the pre-hospital setting. The inability to reliably identify patients that would benefit from primary treatment with endovascular thrombectomy remains an important limitation to optimizing emergency medical services (EMS) triage models and time-to-treatment. Several clinical grading scales that rely solely on clinical examination have been proposed and have demonstrated only moderate predictive ability for ELVO. Consequently, a technology capable of detecting ELVO in the pre-hospital setting would be of great benefit. An analogous scenario existed decades ago, in which pre-hospital detection of acute myocardial infarction (AMI) was unreliable until the emergence of the 12-lead ECG and its adoption by EMS providers. This review details the implementation of pre-hospital ECG (PHECG) for the detection of AMI and explores how early experience with PHECG may be applied to ELVO detection devices, once they become available.

False Activations for ST-Segment Elevation Myocardial Infarction

First-medical-contact-to-device (FMC2D) times have improved over the past decade, as have clinical outcomes for patients presenting with ST-elevation myocardial infarction (STEMI). However, with improvements in FMC2D times, false activation of the cardiac catheterization laboratory (CCL) has become a challenging problem. The authors define false activation as any patient who does not warrant emergent coronary angiography for STEMI. In addition to clinical outcome measures for these patients, STEMI systems should collect data regarding the total number of CCL activations, the total number of emergency coronary angiograms, and the number revascularization procedures performed.

Diagnostic value of prehospital ECG in acute stroke patients

Objective:

To investigate the diagnostic yield of prehospital ECG monitoring provided by emergency medical services in the case of suspected stroke.

Methods:

Consecutive patients with acute stroke admitted to our tertiary stroke center via emergency medical services and with available prehospital ECG were prospectively included during a 12-month study period. We assessed prehospital ECG recordings and compared the results to regular 12-lead ECG on admission and after continuous ECG monitoring at the stroke unit.

Results:

Overall, 259 patients with prehospital ECG recording were included in the study (90.3% ischemic stroke, 9.7% intracerebral hemorrhage). Atrial fibrillation (AF) was detected in 25.1% of patients, second-degree or greater atrioventricular block in 5.4%, significant ST-segment elevation in 5.0%, and ventricular ectopy in 9.7%. In 18 patients, a diagnosis of new-onset AF with direct clinical consequences for the evaluation and secondary prevention of stroke was established by the prehospital recordings. In 2 patients, the AF episodes were limited to the prehospital period and were not detected by ECG on admission or during subsequent monitoring at the stroke unit. Of 126 patients (48.6%) with relevant abnormalities in the prehospital ECG, 16.7% received medical antiarrhythmic therapy during transport to the hospital, and 6.4% were transferred to a cardiology unit within the first 24 hours in the hospital.

Conclusions:

In a selected cohort of patients with stroke, the in-field recordings of the ECG detected a relevant rate of cardiac arrhythmia. The results can add to the in-hospital evaluation and should be considered in prehospital care of acute stroke.

Electrocardiographic diagnosis of ST segment elevation myocardial infarction: An evaluation of three automated interpretation algorithms

OBJECTIVE

To assess the validity of three different computerized electrocardiogram (ECG) interpretation algorithms in correctly identifying STEMI patients in the prehospital environment who require emergent cardiac intervention.

METHODS

This retrospective study validated three diagnostic algorithms (AG) against the presence of a culprit coronary artery upon cardiac catheterization. Two patient groups were enrolled in this study: those with verified prehospital ST-elevation myocardial infarction (STEMI) activation (cases) and those with a prehospital impression of chest pain due to ACS (controls).

RESULTS

There were 500 records analyzed resulting in a case group with 151 patients and a control group with 349 patients. Sensitivities differed between AGs (AG1=0.69 vs AG2=0.68 vs AG3=0.62), with statistical differences in sensitivity found when comparing AG1 to AG3 and AG1 to AG2. Specificities also differed between AGs (AG1=0.89 vs AG2=0.91 vs AG3=0.95), with AG1 and AG2 significantly less specific than AG3.

CONCLUSIONS

STEMI diagnostic algorithms vary in regards to their validity in identifying patients with culprit artery lesions. This suggests that systems could apply more sensitive or specific algorithms depending on the needs in their community.

Chest Pain of Suspected Cardiac Origin: Current Evidence-based Recommendations for Prehospital Care

Introduction

In the United States, emergency medical services (EMS) protocols vary widely across jurisdictions. We sought to develop evidence-based recommendations for the prehospital evaluation and treatment of chest pain of suspected cardiac origin and to compare these recommendations against the current protocols used by the 33 EMS agencies in the state of California.

Methods

We performed a literature review of the current evidence in the prehospital treatment of chest pain and augmented this review with guidelines from various national and international societies to create our evidence-based recommendations. We then compared the chest pain protocols of each of the 33 EMS agencies for consistency with these recommendations. The specific protocol components that we analyzed were use of supplemental oxygen, aspirin, nitrates, opiates, 12-lead electrocardiogram (ECG), ST segment elevation myocardial infarction (STEMI) regionalization systems, prehospital fibrinolysis and β-blockers.

Results

The protocols varied widely in terms of medication and dosing choices, as well as listed contraindications to treatments. Every agency uses oxygen with 54% recommending titrated dosing. All agencies use aspirin (64% recommending 325mg, 24% recommending 162mg and 15% recommending either), as well as nitroglycerin and opiates (58% choosing morphine). Prehospital 12-Lead ECGs are used in 97% of agencies, and all but one agency has some form of regionalized care for their STEMI patients. No agency is currently employing prehospital fibrinolysis or β-blocker use.

Conclusion

Protocols for chest pain of suspected cardiac origin vary widely across California. The evidence-based recommendations that we present for the prehospital diagnosis and treatment of this condition may be useful for EMS medical directors tasked with creating and revising these protocols.

Pre-hospital electrocardiography by emergency medical personnel: effects on scene and transport times for chest pain and ST-segment elevation myocardial infarction patients

OBJECTIVES

This study sought to measure the impact of pre-hospital (PH) electrocardiography (ECG) on scene-to-hospital time for patients with chest pain of cardiac origin and those with ST-segment elevation myocardial infarction (STEMI).

BACKGROUND

Pre-hospital ECG decreases door-to balloon (D2B) time for STEMI patients. However, obtaining a PH ECG might prolong scene time. We investigated the impact of obtaining a PH ECG on both scene and transport times for patients with chest pain suspected of cardiac origin.

METHODS

City of San Diego Emergency Medical System runsheets of patients with chest pain from January 2003 to April 2008 were analyzed. The scene times and transport times were compared before (from January 2003 to December 2005) and after (from January 2006 to April 2008) implementation of the PH ECG. Among patients with a PH ECG, median scene times and transport times were compared in patients with and without STEMI.

RESULTS

There were 21,742 patients evaluated for chest pain during the study period. Implementation of PH ECG resulted in minimal increases in median scene time (19 min, 10 s vs. 19 min, 28 s, p = 0.002) and transport time (13 min, 16 s vs. 13 min, 28 s, p = 0.007). However, compared with chest pain patients, in STEMI patients (n = 303), shorter median scene time (17 min, 51 s vs. 19 min, 31 s, p < 0.001), transport time (12 min, 34 s vs. 13 min, 31 s, p = 0.006), and scene-to-hospital time was observed (30 min, 45 s vs. 33 min, 29 s, p < 0.001).

CONCLUSIONS

Obtaining a PH ECG for patients with chest pain minimally prolongs scene and transport times. Further, for STEMI patients, both scene times and transport times are actually reduced leading to a potential reduction in total ischemic time.

Ability of First-Year Paramedic Students to Identify ST-Segment Elevation Myocardial Injury on 12-Lead Electrocardiogram: A Pilot Study

Introduction:

The purpose of this study was to evaluate the ability of first-year paramedic students to identify ST-segment elevation myocardial injury (STEMI) on 12-lead electrocardiograms (ECGs) following a three-hour presentation by a board-certified emergency medicine physician experienced in ECG interpretation.

Methods:

Thirty-three first-year paramedic students with minimal to no experience in evaluating 12-lead ECGs were administered a pretest with 20 12-lead ECGs and were asked to evaluate each for: (1) presence of STEMI (STEMI identification); (2) if STEMI presents, ECG leads demonstrating ST-elevation (LEAD identification); and (3) if STEMI present, the anatomic distribution of the STEMI (ANATOMY identification). The students were randomized into two groups. Group 1 (16 students; control group) received a handout describing the evaluation of ECGs for STEMI, while Group 2 (17 students; experimental group) received the handout plus a threehour presentation on the evaluation of ECGs for STEMI. Following randomization, distribution of the STEMI handout and ECG STEMI presentation, a posttest with 20 new ECGs was administered to all participants. The pretest and posttest mean scores were compared between the two groups to determine if attendance at the presentation improved the paramedic students' abilities to evaluate and identify STEMI ECGs. Following the STEMI posttest, students in Group 1 were provided with the STEMI lecture. Students were retested with 20 new ECGs five months following the initial study to examine retention of the information taught.

Results:

The mean pre-test scores for the two groups (Group 1 vs Group 2, respectively) in STEMI identification (74.4 vs 75.6%; p = 0.79), lead identification (50.0 vs. 51.2%; p = 0.8) and anatomy identification (49.4 vs 51.8%; p = 0.60) were similar in all three categories. Post-test scores between Group 1 and Group 2 demonstrated statistically significant differences in STEMI identification (85.6 vs 92.4%; p <0.02), lead identification (73.4 vs 85.2%; p <0.02), and anatomy identification (65.9 vs 87.1%; p <0.01), with Group 2 demonstrating higher mean scores relative to Group 1 in all three categories. Comparison of mean initial pre-test and five-month retest scores for all students demonstrated statistically significant differences in STEMI identification (75.0 vs 87.4%; p <0.0001), lead identification (50.6 vs 82.2%; p <0.0001), and anatomy identification (50.6 vs 76.6%; p <0.0001).

Conclusions:

The ability of first-year paramedic students to accurately detect STEMI on prehospital 12-lead ECGs is enhanced by a structured ECG STEMI presentation provided by an emergency medicine physician, and these students maintained excellent retention of STEMI ECG skills over a five-month period.

To transmit or not to transmit: how good are emergency medical personnel in detecting STEMI in patients with chest pain?

BACKGROUND

There is growing use of prehospital electrocardiograms (ECGs) in establishing early diagnosis of ST segment myocardial infarction (STEMI) to facilitate early reperfusion. This study aimed to determine the predictive value of prehospital ECGs interpreted by nonphysician emergency medical services (EMS) in chest pain presentations.

METHODS

In our city of 658,700 people, EMS/paramedics received 21 hours of instruction on STEMI management, ECG acquisition, and interpretation. Suspected STEMI ECGs were wirelessly transmitted to and discussed with a physician for possible therapy. ECGs deemed negative for STEMI by EMS were not transmitted; patients were transported to the closest hospital without prehospital physician involvement.

RESULTS

From July 21, 2008 to July 21, 2010, there were 5426 chest pain calls to EMS, 380 were suspected STEMI cases. The remaining ECGs were deemed negative for STEMI by EMS. To audit the nontransmitted ECGs we analyzed 323 consecutive patients over 2 selected months (January and June 2010) for comparison. Of nontransmitted cases there was 1 missed and 2 STEMIs that developed subsequently. Based on 380 transmitted and 323 nontransmitted cases, the sensitivity and specificity of EMS detecting STEMI were 99.6% and 67.6%, respectively. The positive and negative predictive values for STEMI were 59.5% and 99.7%, respectively.

CONCLUSIONS

Our findings demonstrate nonphysician EMS interpretation of STEMI on prehospital ECG has excellent sensitivity and high negative predictive value. This finding supports the use of prehospital ECGs interpreted by EMS to help identify and facilitate treatment of STEMI. These results may have broad implications on staffing models for first responder/EMS units.

Efficacy of ventilator waveforms observation in detecting patient-ventilator asynchrony

OBJECTIVES

The value of visual inspection of ventilator waveforms in detecting patient-ventilator asynchronies in the intensive care unit has never been systematically evaluated. This study aims to assess intensive care unit physicians' ability to identify patient-ventilator asynchronies through ventilator waveforms.

DESIGN

Prospective observational study.

SETTING

Intensive care unit of a University Hospital.

PATIENTS

Twenty-four patients receiving mechanical ventilation for acute respiratory failure.

INTERVENTION

Forty-three 5-min reports displaying flow-time and airway pressure-time tracings were evaluated by 10 expert and 10 nonexpert, i.e., residents, intensive care unit physicians. The asynchronies identified by experts and nonexperts were compared with those ascertained by three independent examiners who evaluated the same reports displaying, additionally, tracings of diaphragm electrical activity.

MEASUREMENTS AND MAIN RESULTS

Data were examined according to both breath-by-breath analysis and overall report analysis. Sensitivity, specificity, and positive and negative predictive values were determined. Sensitivity and positive predictive value were very low with breath-by-breath analysis (22% and 32%, respectively) and fairly increased with report analysis (55% and 44%, respectively). Conversely, specificity and negative predictive value were high with breath-by-breath analysis (91% and 86%, respectively) and slightly lower with report analysis (76% and 82%, respectively). Sensitivity was significantly higher for experts than for nonexperts for breath-by-breath analysis (28% vs. 16%, p < .05), but not for report analysis (63% vs. 46%, p = .15). The prevalence of asynchronies increased at higher ventilator assistance and tidal volumes (p < .001 for both), whereas it decreased at higher respiratory rates and diaphragm electrical activity (p < .001 for both). At higher prevalence, sensitivity decreased significantly (p < .001).

CONCLUSIONS

The ability of intensive care unit physicians to recognize patient-ventilator asynchronies was overall quite low and decreased at higher prevalence; expertise significantly increased sensitivity for breath-by-breath analysis, whereas it only produced a trend toward improvement for report analysis.

Prehospital electrocardiography: a review of the literature

INTRODUCTION

The American Heart Association and other scientific guidelines recommend emergency medical services acquire prehospital (PH) electrocardiography (ECG) in all patients with symptoms of acute coronary syndrome. The purpose of this article is to critically review the scientific literature about PH ECG.

METHODS

Using multiple search terms, we searched the PubMed and Web of Science databases for relevant information. Search limiters were used: human, research (clinical trials, experimental), core journals, and adult. All articles about the clinical effects of PH ECG published between 2001 and 2011 were retained, in addition to a landmark study from 1997.

RESULTS

Our search yielded a total of 105 articles when all years of publication were considered. When the same search was limited to articles published between 2001 and 2011 for new and current data, 45 articles were returned. A total of 7 articles about the clinical effects of PH ECG were retained for this review. Articles were conceptualized and organized by clinical effects of PH ECG (timing, reperfusion rate, death, ejection fraction, reinfarction, and stroke). PH ECG has been associated with reduced PH delay time, increased use of reperfusion interventions, earlier diagnosis, and faster time to treatment.

DISCUSSION

PH ECG plays a major role in emergency cardiac systems of care and can facilitate early intervention by identifying patients with acute coronary syndrome sooner.

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

AIMS/METHODS

We 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.

RESULTS

The 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).

CONCLUSIONS

Prehospital ECG data obtained with 12-lead ST-segment monitoring provides diagnostic information about ACS above and beyond the initial hospital ECG.

[Can we improve the management of acute coronary syndromes in primary care?]

OBJECTIVE

To evaluate a training programme in the primary care of acute coronary syndrome.

DESIGN

A before-during-after comparative cross-sectional study.

SETTING

Health areas of Lleida, High Pyrenees and Aran (Spain), from 2003-2006.

PARTICIPANTS

Patients with acute coronary syndrome admitted to the intensive medicine unit and the coronary unit of the Arnau de Vilanova University Hospital of Lleida after being referred from home, general practitioner or health centre.

INTERVENTION

A training program was introduced to establish protocols of pre-hospital performance in acute coronary syndrome (the administration of acetylsalicylic acid, nitroglycerin and morphine chloride, the performing of an electrocardiogram, the insertion of an intravenous tube and to speed up care times).

MAIN MEASURES

Linear trend of the three periods of the study was analyzed through prevalences ratio and linear trend test.

RESULTS

The intervention showed a statistically significant linear increase in the application of the aforementioned therapeutic procedures, with the exception of nitroglycerin, which started out with a higher baseline level, and an improvement of care times. The application of an electrocardiogram obtained almost optimal levels. Care times considerably improved.

CONCLUSIONS

Training programs are a useful tool in improving treatment of acute coronary syndromes in primary care. Advance diagnosis and an early start to treatment almost certainly results in a decrease of its morbidity-mortality.

Can paramedics read ST-segment elevation myocardial infarction on prehospital 12-lead electrocardiograms?

INTRODUCTION

Activation of the cardiac catheterization laboratory prior to patient arrival at the hospital, based on a prehospital 12-lead electrocardiogram (ECG), reduces door-to-balloon time by 10-55 minutes for patients with ST-segment elevation myocardial infarction (STEMI). In emergency medical services (EMS) systems where transmission of the ECG to the emergency department (ED) is not feasible, the ability of paramedics to accurately read 12-lead ECGs is crucial to the success of a prehospital catheterization laboratory activation program. Objective. To determine whether paramedics can accurately diagnose STEMI on a prehospital 12-lead ECG and decide to activate the cardiac catheterization laboratory appropriately.

METHODS

Five chest pain scenarios were generated, with standardized prehospital ECGs accompanying each: three STEMI cases that should result in catheterization laboratory activation and two non-STEMI cases that should not. A convenience sample of paramedics in an urban/suburban EMS system examined each scenario and ECG, and indicated whether the patient had STEMI and whether they would activate the catheterization laboratory. A series of demographic and operational questions were also asked of each participant. We report diagnostic statistics, agreement (kappa), and 95% confidence intervals (CIs).

RESULTS

A convenience sample of 103 of 147 eligible paramedics (70%) was enrolled. For STEMI diagnosis, paramedics' sensitivity was 92.6% (95% CI 88.9-95.1) and specificity was 85.4% (79.7-89.8); for catheterization laboratory activation, sensitivity was 88.0% (83.8-91.3) and specificity was 88.3% (83.0-92.2). False-positive activation of the catheterization laboratory occurred in 8.1% (5.4-12.0) of cases. Of the STEMI cases, 94.1% were correctly read as STEMI, and 91.0% had the catheterization laboratory appropriately activated. Of the non-STEMI cases, 14.9% were incorrectly read as STEMI, and 12.0% had the catheterization laboratory inappropriately activated. The paramedics' comfort with calling a "chest pain alert" with no resulting catheterization laboratory activation (the current practice in this system) was not statistically different from their comfort with calling a chest pain alert if that call were to automatically result in catheterization laboratory activation (p > 0.05).

CONCLUSIONS

Paramedics in an urban/suburban EMS system can diagnose STEMI and identify appropriate cardiac catheterization laboratory activations with a high degree of accuracy, and an acceptable false-positive rate, when tested using paper-based scenarios.

Meta-analysis of diagnostic studies: a comparison of random intercept, normal-normal, and binomial-normal bivariate summary ROC approaches

BACKGROUND

Using data from a published meta-analysis of magnetic resonance imaging of the menisci and cruciate ligaments, the authors varied the overall sensitivity and specificity, the between-studies variance, the within-study sample size, and the number of studies to evaluate the performances of the 3 methods in a simulation study. The parameters to be compared are the associated intercept, slope, and residual variance, using bias, mean squared error, and coverage probabilities.

RESULTS

The BN method always gave unbiased estimates of the intercept and slope parameter. The coverage probabilities were also reasonably acceptable, unless the number of studies was very small. In contrast, the RI and NN methods could produce large biases with poor coverage probabilities, especially when sample sizes of individual studies were small or when sensitivities or specificities were close to 1. Although this was rare in the simulations, the bivariate methods can suffer from nonconvergence mostly due to the correlation being close to +/- 1.

CONCLUSION

The binomial-normal model performed better than the other recently introduced methods for meta-analysis of data from studies of test performance.

The accuracy of an out-of-hospital 12-lead ECG for the detection of ST-elevation myocardial infarction immediately after resuscitation

STUDY OBJECTIVE

Severe myocardial ischemia is the leading cause of arrhythmic sudden cardiac death. It is unclear, however, in which percentage of patients sudden cardiac death is triggered by ST-elevation myocardial infarction (STEMI) and whether the diagnosis of STEMI can be reliably established immediately after resuscitation from out-of-hospital sudden cardiac death.

METHODS

A 12-lead ECG was registered after return of spontaneous circulation after cardiac arrest. After hospital admission, further ECG, creatine kinase MB, and troponin measures; results of coronary angiograms; and autopsies were evaluated to confirm the definitive diagnosis of STEMI.

RESULTS

Seventy-seven patients were included in our study (67% men, age 64 [14 to 93] years). STEMI was diagnosed in 44 patients. The diagnosis of myocardial infarction was confirmed in 84% of the 77 patients who survived to hospital admission. The sensitivity of the out-of-hospital ECG was 88% (95% confidence interval [CI] 74% to 96%), the specificity 69% (95% CI 51% to 83%), the positive predictive value 77% (95% CI 62% to 87%), and the negative predictive value 83% (95% CI 64% to 87%). The accuracy of the out-of-hospital ECG and that registered on admission was the same.

CONCLUSION

The diagnosis of STEMI can be established in the field immediately after return of spontaneous circulation in most patients. This may enable an early decision about reperfusion therapy, ie, immediate out-of-hospital thrombolysis or targeted transfer for percutaneous coronary intervention.

Randomisation to protect against selection bias in healthcare trials

BACKGROUND

Randomised trials use the play of chance to assign participants to comparison groups. The unpredictability of the process, if not subverted, should prevent systematic differences between comparison groups (selection bias), provided that a sufficient number of people are randomised.

OBJECTIVES

To assess the effects of randomisation and concealment of allocation on the results of healthcare trials.

SEARCH STRATEGY

We searched the Cochrane Methodology Register, MEDLINE, SciSearch, reference lists up to August 2000 and used personal communication.

SELECTION CRITERIA

Cohorts of trials, systematic reviews or meta-analyses of healthcare interventions that compared outcomes or prognostic factors for one of the following comparisons: randomised versus non-randomised trials, randomised trials with adequately versus inadequately concealed allocation, or high versus low quality trials where selection bias could not be separated from other sources of bias.

DATA COLLECTION AND ANALYSIS

One of us went through all of the citations in the Cochrane Methodology Register and accumulated reference lists. Studies that appeared to meet the inclusion criteria were retrieved and assessed independently by two of the reviewers. The methodological quality of included studies was appraised and information extracted by one of us and checked by a second. Tabular summaries of the results were prepared for each comparison and the results across studies were assessed qualitatively to identify common trends or discrepancies.

MAIN RESULTS

We identified 32 studies including over 3000 trials. Twenty-two studies compared randomised versus non-randomised trials, three compared adequately versus inadequately concealed allocation, and nine compared high versus low quality trials (some studies included more than one comparison). Five studies were of high methodological quality. In 15 of the 22 studies that compared randomised and non-randomised trials of the same intervention, important differences were found in the estimates of effect. Some of these differences were due to a poorer prognosis in the control groups in the non-randomised trials. The results of the other seven studies that compared randomised and non-randomised trials across different interventions are less clear. Comparisons of adequately and inadequately concealed allocation in randomised trials of the same intervention provided high quality evidence that concealment can be crucial in achieving similar treatment groups and, therefore, unbiased estimates of treatment effects. Studies with inadequate concealment tended to overestimate treatment effects. Comparisons of high and low quality trials of the same intervention have found important differences in estimates of effect, but it is not possible to determine the extent to which these differences can be attributed to randomisation or concealment of allocation. Omitting comparisons between randomised trials and non-randomised trials using historical controls did not substantially alter the results or conclusions of our review.

AUTHORS' CONCLUSIONS

On average, non-randomised trials and randomised trials with inadequate concealment of allocation tend to result in larger estimates of effect than randomised trials with adequately concealed allocation. However, it is not generally possible to predict the magnitude, or even the direction, of possible selection biases and consequent distortions of treatment effects.

[Acute coronary syndrome. Guideline-conform management by regional and interregional care concepts]

BACKGROUND

The acute coronary syndrome (ACS) with 16% is one of the most common indication for emergency missions. Care of ACS patients in the Heidelberg emergency service region has been carried out since the beginning of 2005 following an interdisciplinary developed concept based on the current guidelines of the German Society for Cardiology (DGK), the American College of Cardiology (ACC), the American Heart Association (AHA), the European Society of Cardiology (ESC) and the European Resuscitation Council (ERC).

MATERIALS AND METHODS

Evaluation of the emergency diagnostic and therapeutic measures for the diagnosis of ACS before and after the introduction of the ACS care concept, was carried out retrospectively for the years 2004 (group 1) and 2005 (group 2) by electronic data processing of the records stored in the emergency medical services documentaion system (NADOK).

RESULTS

In the years 2004 before (group 1, n=633) and 2005 after (group 2, n=628) introduction of the ACS care concept, there was a comparable basic diagnostic consisting of a 3-lead electrocardiogram (ECG; 95 versus 97%), manual blood pressure measurement (93 versus 95%) and pulse oxymetry (94 versus 91%) as well as a comparable proportion of patients who received a peripheral vene access (99 versus 100%). There were no significant differences between the two groups. However, after the introduction of the ACS concept, the 12-lead ECG was used significantly more often (49 versus 71%, p=0.0001). Furthermore, a guideline-conform medicinal treatment of ACS patients was used inceasingly more often for anticoagulation with heparin/acetylsalicylic acid (75 versus 84%,p=0.0001) and the use of beta-receptor blockers (32 versus 39%, p=0.009) after introduction of the ACS concept.

CONCLUSIONS

The introduction of a regional care concept leads to an optimisation of guideline-conform prehospital treatment for ACS patients.

Utilisation and clinical efficacy of echocardiography in a regional hospital

OBJECTIVE

To determine utilisation and clinical efficacy of echocardiography in a regional setting.

DESIGN

Consecutive patients referred for echocardiography studied prospectively using a pro-forma to be completed before and after echocardiography.

SETTING

Regional hospital in New South Wales.

PARTICIPANTS

A total of 103 consecutive patients.

MAIN OUTCOME MEASURES

Utilisation and clinical efficacy of echocardiography.

RESULTS

No significant abnormalities were detected in 41.7% of patients, but unexpected abnormalities were found in 31.1%. For 60% of pretest diagnoses there was a clinically important change in diagnostic certainty following the test and changes to treatment occurred in 30.1% of patients. A total of 19 patients with neurological events underwent echocardiography but none had cardiac thrombus demonstrated although thrombus was demonstrated in additional seven.

CONCLUSIONS

Echocardiography appears to be used appropriately in our regional setting, resulting in major changes to diagnostic certainty and leading to alterations to treatments in almost one-third of patients. Education in relation to the use of echocardiography in patients with neurological events is warranted.

Prehospital 12-lead electrocardiography impact on acute myocardial infarction treatment times and mortality: a systematic review

OBJECTIVES

Prehospital 12-lead electrocardiogram (PHECG) interpretation and advance emergency department (ED) notification may improve time-to-treatment intervals for a variety of treatment strategies to improve outcome in acute myocardial infarction. Despite consensus guidelines recommending this intervention, few emergency medical services (EMS) employ this. The authors systematically reviewed the literature to report whether mortality or treatment time intervals improved when compared with standard care.

METHODS

The authors used the Cochrane strategy to search MEDLINE, EMBASE, Current Contents, Dissertation Abstracts, Cochrane Library, and Index of Scientific and Technical Proceedings. Bibliographies and grant-agency Websites were reviewed, and primary investigators and industry were contacted for published and unpublished studies. Inclusion criteria included PHECG and advance ED notification versus standard EMS care; controlled trials; English only; and evaluation of treatment time intervals, all-cause mortality, or both. Study selection was hierarchical, blinded, and independent. Agreement at each level of review was evaluated by using a kappa statistic. Study quality was measured with a validated scale and was interpreted by two independent reviewers.

RESULTS

A total of 1,283 citations were identified, and five studies met the inclusion criteria. The weighted kappa for selection was 0.61 (standard error [SE], 0.045) for titles, 0.63 (SE, 0.051) for abstracts, and 0.79 (SE, 0.146) for full articles. Mean study quality measures by two independent reviewers were 6.0/15 and 5.5/15 (correlation coefficient, 0.85; p = 0.06). PHECG and advance ED notification increased the weighted mean on-scene time by 1.2 minutes (95% confidence interval [95% CI] = -0.84 to 3.2). The weighted mean door-to-needle interval was shortened by 36.1 minutes (95% CI = 9.3 to 63.0: range of means, 22-48 minutes vs. 50-97 minutes). One study reported all-cause mortality, with a statistically nonsignificant reduction from 15.6% to 8.4%.

CONCLUSIONS

For patients with AMI, the literature would suggest that PHECG and advanced ED notification reduces in hospital time to fibrinolysis. One controlled trial found no difference in mortality with this out-of-hospital intervention.

Emergency Medical Service Aspects of Emergency Cardiac Care

Prehospital intervention has the potential for significantly affecting the outcome of cardiovascular emergencies. The authors examine multiple issues in prehospital care that can streamline and improve cardiac care. Improving access to prehospital care and increasing the use of the emergency medical services (EMS) system can speed interventions to the patients. The use of ECG in the out-of-hospital setting can reduce time to definitive treatment. Issues, such as the use of public access defibrillation and interfacility transports are also discussed.

The prehospital 12-lead electrocardiogram's effect on time to initiation of reperfusion therapy: a systematic review and meta-analysis of existing literature

The prehospital electrocardiogram (ECG) is becoming the standard of care of suspected cardiac chest pain. We evaluated the evidence regarding the prehospital ECG and sought to quantify the reduction in time to reperfusion therapy attributable to the prehospital ECG. We conducted a systematic review and analyzed studies that were conducted in emergency medical systems relevant to providers in the United States. The papers were limited to studies that reported original data that compared prehospital ECG to no prehospital ECG groups. Four studies containing 99 patients met the inclusion criteria. A meta-analysis of these studies revealed a difference of 24.7 (95% confidence interval, 16.7-32.7) minutes. Providers now have a quantified value of the prehospital ECG based on the best published evidence. In addition, this search showed a relatively low quality and quantity of research on the prehospital ECG.

How do Belgian mobile intensive care units deal with cardiovascular emergencies?

OBJECTIVES

To assess the availability and use of diagnostic tools, therapeutic equipment and drugs for the prehospital treatment of acute coronary syndromes, cardiopulmonary arrest and other cardiovascular emergencies in Belgian physician-staffed and hospital-based mobile intensive care units.

METHODS

In April 2001, a questionnaire was sent to all Belgian mobile intensive care unit centres.

RESULTS

The response rate was 90%. There was a 100% availability of many drugs and therapeutic equipment, with a well-established role in the care of cardiovascular emergencies: defibrillators, nitrates, epinephrine, atropine and diuretics. Important emergency drugs and tools were not ubiquitously available: external pacemakers (90%), aspirin (90%), bicarbonate (99%), amiodarone (87%), and intravenous beta-blockers (75%). Twelve-lead electrocardiogram recorders and thrombolytics had a rather low availability (46 and 20%, respectively) and were rarely used. There was a high availability of some drugs with limited data to support their use: oral calcium antagonists (61%), bretylium (65%) and isoproterenol (92%).

CONCLUSIONS

In Belgian mobile intensive care units the availability and use of technical and diagnostic equipment and cardiac drugs varied to an important extent. A local multidisciplinary evaluation may improve prehospital cardiovascular care by implementing current guidelines.

Diagnosing acute cardiac ischemia in the emergency department: a systematic review of the accuracy and clinical effect of current technologies

STUDY OBJECTIVE

Acute cardiac ischemia (ACI) encompasses the diagnoses of unstable angina pectoris and acute myocardial infarction (AMI). Accurate diagnosis and triage of patients with ACI in the emergency department should increase survival for these patients and reduce unnecessary hospital admissions.

METHODS

We conducted a systematic review of the English-language literature published between 1966 and December 1998 on the accuracy and clinical effect of diagnostic technologies for ACI. We evaluated prospective and retrospective studies of adult patients who presented to the ED with symptoms suggesting ACI. Outcomes were diagnostic performance (test sensitivity and specificity) and measures of clinical effect. Meta-analyses were performed when appropriate. A decision and cost-effectiveness analysis was conducted that investigated various diagnostic strategies used in the diagnosis of ACI in the ED.

RESULTS

We screened 6,667 abstracts, reviewed 407 full articles, and included 106 articles articles in the main analysis. Single measurements of biomarkers at presentation to the ED have low sensitivity for AMI, although they have high specificity. Serial measurements greatly increase the sensitivity for AMI while maintaining their excellent specificity. Diagnostic technologies to evaluate ACI in selected populations, such as electrocardiography, sestamibi perfusion imaging, and stress ECG, may have very good to excellent sensitivity; however, they have not been sufficiently studied. The Goldman Chest Pain Protocol has good sensitivity (about 90%) for AMI but has not been shown to result in any differences in hospitalization rate, length of stay, or estimated costs in the single clinical effect study performed. Its applicability to patients with unstable angina pectoris has not been evaluated. The use of an Acute Cardiac Ischemia-Time-Insensitive Predictive Instrument led to the appropriate triage of 97% of patients with ACI presenting to the ED and reduced unnecessary hospitalizations.

CONCLUSION

Many of the current technologies remain underevaluated, especially regarding their clinical effect. The extent to which combinations of tests may provide better accuracy than any single test needs further study.