Retrospective Description and Analysis of Consecutive Catheterization Laboratory ST-Segment Elevation Myocardial Infarction Activations With Proposal, Rationale, and Use of a New Classification Scheme

Rationale and design of the artificial intelligence scalable solution for acute myocardial infarction (ASSIST) study

BACKGROUND

Acute coronary syndrome (ACS), specifically ST-segment elevation myocardial infarction is a major cause of morbidity and mortality throughout Europe. Diagnosis in the acute setting is mainly based on clinical symptoms and physician's interpretation of an electrocardiogram (ECG), which may be subject to errors. ST-segment elevation is the leading criteria to activate urgent reperfusion therapy, but a clear ST-elevation pattern might not be present in patients with coronary occlusion and ST-segment elevation might be seen in patients with normal coronary arteries.

METHODS

The ASSIST project is a retrospective observational study aiming to improve the ECG-assisted assessment of ACS patients in the acute setting by incorporating an artificial intelligence platform, Willem™ to analyze 12‑lead ECGs. Our aim is to improve diagnostic accuracy and reduce treatment delays. ECG and clinical data collected during this study will enable the optimization and validation of Willem™. A retrospective multicenter study will collect ECG, clinical, and coronary angiography data from 10,309 patients. The primary outcome is the performance of this tool in the correct identification of acute myocardial infarction with coronary artery occlusion. Model performance will be evaluated internally with patients recruited in this retrospective study while external validation will be performed in a second stage.

CONCLUSION

ASSIST will provide key data to optimize Willem™ platform to detect myocardial infarction based on ECG-assessment alone. Our hypothesis is that such a diagnostic approach may reduce time delays, enhance diagnostic accuracy, and improve clinical outcomes.

Late Outcomes of Patients With Prehospital ST-Segment Elevation and Appropriate Cardiac Catheterization Laboratory Nonactivation

Background Patients with suspected ST-segment-elevation myocardial infarction (STEMI) and cardiac catheterization laboratory nonactivation (CCL-NA) or cancellation have reportedly similar crude and higher adjusted risks of death compared with those with CCL activation, though reasons for these poor outcomes are not clear. We determined late clinical outcomes among patients with prehospital ECG STEMI criteria who had CCL-NA compared with those who had CCL activation. Methods and Results We identified consecutive prehospital ECG transmissions between June 2, 2010 to October 6, 2016. Diagnoses according to the Fourth Universal Definition of myocardial infarction (MI), particularly rates of myocardial injury, were adjudicated. The primary outcome was all-cause death. Secondary outcomes included cardiovascular death/MI/stroke and noncardiovascular death. To explore competing risks, cause-specific hazard ratios (HRs) were obtained. Among 1033 included ECG transmissions, there were 569 (55%) CCL activations and 464 (45%) CCL-NAs (1.8% were inappropriate CCL-NAs). In the CCL activation group, adjudicated index diagnoses included MI (n=534, 94%, of which 99.6% were STEMI and 0.4% non-STEMI), acute myocardial injury (n=15, 2.6%), and chronic myocardial injury (n=6, 1.1%). In the CCL-NA group, diagnoses included MI (n=173, 37%, of which 61% were non-STEMI and 39% STEMI), chronic myocardial injury (n=107, 23%), and acute myocardial injury (n=47, 10%). At 2 years, the risk of all-cause death was higher in patients who had CCL-NA compared with CCL activation (23% versus 7.9%, adjusted risk ratio, 1.58, 95% CI, 1.24-2.00), primarily because of an excess in noncardiovascular deaths (adjusted HR, 3.56, 95% CI, 2.07-6.13). There was no significant difference in the adjusted risk for cardiovascular death/MI/stroke between the 2 groups (HR, 1.23, 95% CI, 0.87-1.73). Conclusions CCL-NA was not primarily attributable to missed STEMI, but attributable to "masquerading" with high rates of non-STEMI and myocardial injury. These patients had worse late outcomes than patients who had CCL activation, mainly because of higher rates of noncardiovascular deaths.

Impact of Pre-Hospital Activation of STEMI on False Positive Activation Rate and Door to Balloon Time

BACKGROUND

Pre-hospital identification of ST-segment elevation myocardial infarction (STEMI) by paramedical staff reduces reperfusion time. However, the impact of this approach on the rate of unnecessary activation of coronary catheterisation lab (CCL) remains unclear.

METHODS

The study reviewed consecutive STEMI patients over 3 years (July 2015 to June 2018) from all primary percutaneous coronary intervention (PPCI) centres and inter-hospital transfers (IHT) from non-PPCI capable centres in Western Australia. Out-of-hospital cardiac arrests (OOHCA) and STEMI calls for in-patients receiving treatment for other medical reasons were excluded.

RESULTS

During the 3 years study period, 1,736 STEMI cases were recorded. Pre-hospital (PH) activation occurred in 799 (46%) cases. Median door to balloon time (D2BT) was 68 minutes (IQR 63 mins). D2BT for PH activation (40 min [IQR 25 min]) was significantly lower than both the PPCI centre emergency department (ED) activation (86 min [IQR 55 min]) and IHT activation groups (108 min [IQR 55 min]), p-value <0.00001. In PH activation group 98% patients received primary PCI in less than 90 minutes compared to 54% and 26% patients in the ED and the IHT activation groups, respectively. False positive STEMI activation rate was lower in the PH activation group (2.75%) compared to ED activation (5.4%) and IHT group (6%), p-value 0.0115. The false positive rate did not vary significantly between working hours and out-of-hour calls (5% vs 4%, p-value=0.304). Pericarditis, coronary artery disease other than STEMI, atypical chest pain, and stress induced cardiomyopathy were the common diagnoses in false positive activations.

CONCLUSION

Pre-hospital activation of STEMI leads to reduced door to balloon times without a significant increase in inappropriate procedures, though false positive activation rates are unclear. The majority of STEMI patients transferred from non-PPCI centres failed to receive reperfusion therapy within 90 minutes of initial hospital presentation. Further studies are required to assess the benefits of thrombolysis in selected patients in inter-hospital transfer group.

Rational and design of ST-segment elevation not associated with acute cardiac necrosis (LESTONNAC). A prospective registry for validation of a deep learning system assisted by artificial intelligence

BACKGROUND

Patients with chest pain and persistent ST segment elevation (STE) may not have acute coronary occlusions or serum troponin curves suggestive of acute necrosis. Our objective is the validation and cost-effectiveness analysis of a diagnostic model assisted by artificial intelligence (AI).

METHODS

Prospective multicenter registry in two groups of patients with STE: I) coronary arteries without significant lesions and without serum troponin curve suggestive of acute necrosis, II) myocardial infarction with acute coronary occlusion. The inclusion criteria are the following: 1) age ≥ 18 years, 2) chest pain or symptoms suggestive of myocardial ischemia, 3) STE at point J in two contiguous leads ≥0.1 mV, in V2 and V3 ≥ 0,2 mV and 4) signature of informed consent. The exclusion criteria are the following: 1) left bundle branch block, 2) acute cardiac necrosis in the absence of significant epicardial coronary artery stenosis, 3) STE ≤ 0.1 mV with pathologic Q wave, 4) severe anemia (hemoglobin <8.0 g/dl). For each patient without acute cardiac necrosis, the next patient from that center of the same sex and similar age (± 5 years) with myocardial infarction and acute coronary occlusion will be included. A manual centralized electrocardiographic analysis and another by deep learning AI will be performed.

CONCLUSIONS

The results of the study will provide new information for the stratification of patients with STE. Our hypothesis is that an AI analysis of the surface electrocardiogram allows a better distinction of patients with STE due to acute myocardial ischemia, from those with another etiology.

Five years of Stent for Life in Portugal

OBJECTIVE

To analyze changes in performance indicators five years after Portugal joined the Stent for Life (SFL) initiative.

METHODS

National surveys were carried out annually over one-month periods designated as study Time Points between 2011 (Time Zero) and 2016 (Time Five). In this study, 1340 consecutive patients with suspected ST-elevation myocardial infarction (STEMI) who underwent coronary angiography, admitted to 18 24/7 primary percutaneous coronary intervention (PCI) centers, were enrolled.

RESULTS

There was a significant reduction in the proportion of patients who attended primary healthcare centers (20.3% vs. 4.8%, p<0.001) and non-PCI-capable centers (54.5% vs. 42.5%, p=0.013). The proportions of patients who called 112, the national emergency medical services (EMS) number (35.2% vs. 46.6%, p=0.022) and of those transported via the EMS to a PCI-capable center (13.1% vs. 30.5%, p<0.001) increased. The main improvement observed in timings for revascularization was a trend toward a reduction in patient delay (114 min in 2011 vs. 100 min in 2016, p=0.050). System delay and door-to-balloon time remained constant, at a median of 134 and 57 min in 2016, respectively.

CONCLUSION

During the lifetime of the SFL initiative in Portugal, there was a positive change in patient delay indicators, especially the lower proportion of patients who attended non-PCI centers, along with an increase in those who called 112. System delay did not change significantly over this period. These results should be taken into consideration in the current Stent - Save a Life initiative.

Mobile application to optimize care for ST-segment elevation myocardial infarction patients in a large healthcare system, STEMIcathAID: rationale and design

Aims

Technological advancements have transformed healthcare. System delays in transferring patients with ST-segment elevation myocardial infarction (STEMI) to a primary percutaneous coronary intervention (PCI) centre are associated with worse clinical outcomes. Our aim was to design and develop a secure mobile application, STEMIcathAID, streamlining communication, and coordination between the STEMI care teams to reduce ischaemia time and improve patient outcomes.

Methods and results

The app was designed for transfer of patients with STEMI to a cardiac catheterization laboratory (CCL) from an emergency department (ED) of either a PCI capable or a non-PCI capable hospital. When a suspected STEMI arrives to a non-PCI hospital ED, the ED physician uploads the electrocardiogram and relevant patient information. An instant notification is simultaneously sent to the on-call CCL attending and transfer centre. The attending reviews the information, makes a video call and decides to either accept or reject the transfer. If accepted, on-call CCL team members receive an immediate push notification and begin communicating with the ED team via a HIPAA compliant chat. The app provides live GPS tracking of the ambulance and frequent clinical status updates of the patient. In addition, it allows for screening of STEMI patients in cardiogenic shock. Prior to discharge, important data elements have to be entered to close the case.

Conclusion

We developed a novel mobile app to optimize care for STEMI patients and facilitate electronic extraction of relevant performance metrics to improve allocation of resources and reduction of costs.

Effect of Real-Time Physician Oversight of Prehospital STEMI Diagnosis on ECG-Inappropriate and False Positive Catheterization Laboratory Activation

Background

ST-elevation myocardial infarction diagnosis at first medical contact (FMC) and prehospital cardiac catheterization laboratory (CCL) activation are associated with reduced total ischemic time and therefore have become the dominant ST-elevation myocardial infarction referral method in primary percutaneous coronary intervention systems. We sought to determine whether physician oversight was associated with improved diagnostic performance in a prehospital CCL activation system and what effect the additional interpretation has on treatment delay.

Methods

Between 2012 and 2015, all patients in 2 greater Montreal catchment areas with a chief symptom of chest paint or dyspnea had an in-the-field electrocardiogram (ECG). A machine diagnosis of "acute myocardial infarction" resulted either in automatic CCL (automated cohort without oversight) or transmission of the ECG to the receiving centre emergency physician for reinterpretation before CCL activation. System performance was assessed in terms of the proportion of false positive and inappropriate activations (IA), as well as the proportion of patients with FMC-to-device times ≤ 90 minutes.

Results

Four hundred twenty-eight (428) activations were analyzed (311 automated; 117 with physician oversight). Physician oversight tended to decrease IAs (7% vs 3%; P = 0.062), but was also associated with a smaller proportion of patients achieving target FMC-to-device (76% vs 60%; P < 0.001). There was no significant effect on the proportion of false positive activation.

Conclusions

Real-time physician oversight might be associated with fewer IAs, but also appears to have a deleterious effect on FMC-to-device performance. Identifying predictors of IA could improve overall performance by selecting ECGs that merit physician oversight and streamlining others. Larger clinical studies are warranted.

Hybrid Network with Attention Mechanism for Detection and Location of Myocardial Infarction Based on 12-Lead Electrocardiogram Signals

The electrocardiogram (ECG) is a non-invasive, inexpensive, and effective tool for myocardial infarction (MI) diagnosis. Conventional detection algorithms require solid domain expertise and rely heavily on handcrafted features. Although previous works have studied deep learning methods for extracting features, these methods still neglect the relationships between different leads and the temporal characteristics of ECG signals. To handle the issues, a novel multi-lead attention (MLA) mechanism integrated with convolutional neural network (CNN) and bidirectional gated recurrent unit (BiGRU) framework (MLA-CNN-BiGRU) is therefore proposed to detect and locate MI via 12-lead ECG records. Specifically, the MLA mechanism automatically measures and assigns the weights to different leads according to their contribution. The two-dimensional CNN module exploits the interrelated characteristics between leads and extracts discriminative spatial features. Moreover, the BiGRU module extracts essential temporal features inside each lead. The spatial and temporal features from these two modules are fused together as global features for classification. In experiments, MI location and detection were performed under both intra-patient scheme and inter-patient scheme to test the robustness of the proposed framework. Experimental results indicate that our intelligent framework achieved satisfactory performance and demonstrated vital clinical significance.

Cancellation of the Cardiac Catheterization Lab After Activation for ST-Segment-Elevation Myocardial Infarction

BACKGROUND

Prehospital ECG-based cardiac catheterization laboratory (CCL) activation for ST-segment-elevation myocardial infarction reduces door-to-balloon times, but CCL cancellations (CCL^X) remain a challenging problem. We examined the reasons for CCL^X, clinical characteristics, and outcomes of patients presenting as ST-segment-elevation myocardial infarction activations who receive emergent coronary angiography (EA) compared with CCL^X.

METHODS AND RESULTS

We reviewed all consecutive CCL activations between January 1, 2012, and December 31, 2014 (n=1332). Data were analyzed comparing 2 groups stratified as EA (n=466) versus CCL^X (n=866; 65%). Reasons for CCL^X included bundle branch block (21%), poor-quality prehospital ECG (18%), non-ST-segment-elevation myocardial infarction ST changes (18%), repolarization abnormality (13%), and arrhythmia (8%). A multivariate logistic regression model using age, peak troponin, and initial ECG findings had a high discriminatory value for determining EA versus CCL^X (C statistic, 0.985). CCL^X subjects were older and more likely to be women, have prior coronary artery bypass grafting, or a paced rhythm ( P<0.0001 for all). All-cause mortality did not differ between groups at 1 year or during the study period (mean follow-up, 2.186±1.167 years; 15.8% EA versus 16.2% CCL^X; P=0.9377). Cardiac death was higher in the EA group (11.8% versus 3.0%; P<0.0001). After adjusting for clinical variables associated with survival, CCL^X was associated with an increased risk for all-cause mortality during the study period (hazard ratio, 1.82; 95% CI, 1.28-2.59; P=0.0009).

CONCLUSIONS

In this study, prehospital ECG without overreading or transmission lead to frequent CCL^X. CCL^X subjects differ with regard to age, sex, risk factors, and comorbidities. However, CCL^X patients represent a high-risk population, with frequently positive cardiac enzymes and similar short- and long-term mortality compared with EA. Further studies are needed to determine how quality improvement initiatives can lower the rates of CCL^X and influence clinical outcomes.

Sensitivity and specificity of the Vectraplex electrocardiogram system with a cardiac electric biomarker in the diagnosis of ST-elevation myocardial infarction

ST-elevation myocardial infarction (STEMI) is a clinical diagnosis based on a compatible history and characteristic electrocardiographic changes. In the current era, STEMI is treated emergently with angiography, leading to percutaneous coronary intervention. However, false-positive electrocardiograms (ECGs) occur, resulting in unnecessary emergent catheterizations. We hypothesized that the Vectraplex cardiac electrical biomarker (CEB) would increase the specificity for the diagnosis of STEMI. We studied 50 patients who were identified by standard of care (clinical history, physical exam, and 12-lead ECG) as suspected to have STEMI and tested the sensitivity and specificity of the Vectraplex ECG system. Using the final clinical diagnosis (based on history, ECGs, troponin values, and angiographic findings) as the gold standard, we found the CEB value to be quite dynamic, with a reasonable sensitivity and a good positive predictive value but generally poor specificity and negative predictive value. It offered only a 20% improvement compared to 50-50 performance on receiver operator curves.

False activation of the cardiac catheterization laboratory: The price to pay for shorter treatment delay

Introduction

In patients with acute ST elevation myocardial ischemia (STEMI), national efforts have focused on reducing door-to-balloon (D2B) times for primary percutaneous coronary intervention (PCI). This emphasis on time-to-treatment may increase the rate of inappropriate cardiac catheterization laboratory (CCL) activations and unnecessary healthcare utilization. To achieve lower D2B times, community hospitals and EMS systems have enabled emergency medical technicians (EMTs) and emergency department (ED) physicians to activate the CCLs without immediately consulting a cardiologist.

Objective

The purpose of this study is to determine the rate and main causes of inappropriate activation of the CCL which will aid in finding solutions to reduce this occurrence.

Method

This is a retrospective study, based on an electronic medical system review of all inappropriate CCL activation who presented to Providence Hospital and Medical Centers (PHMC) in Michigan, from January 2015 to July 2016.

Results

The CCL was activated 375 times for suspected STEMI. The false STEMI activation was identified in 47 patients which represents 12.5% of total CCL activation. The vast majority of this false activation was due to non-diagnostic electrocardiogram (ECG) that did not meet the STEMI criteria.

Conclusion

The subjective interpretation of the ECG by EMTs and ED physicians tend to show a wide variability, which may lead to higher-than-anticipated false activation rates of up to 36% in one study. Some studies had reported that up to 72% of inappropriate activations were caused by ECG misinterpretations. These false activations have ramifications that lead to both clinical and financial costs.

Accurate Prediction of False ST-Segment Elevation Myocardial Infarction: Ready for Prime Time?

The incidence of inappropriate cardiac catheterization lab activation for treatment of a false ST-segment elevation myocardial infarction (STEMI) has been reported to be 2.6%-36%. Excessive inappropriate catheterization lab activation may be associated with risks to patients, provider fatigue and improper resource usage.

HYPOTHESIS

To derive and validate a prediction score to more accurately classify patients with STEMI.

METHODS AND RESULTS

We conducted a retrospective cohort analysis of 1144 consecutive patients initially diagnosed with STEMI between September 2008 and January 2013. The incidence of catheterization laboratory activation for false STEMI was 21.4%. Multiple logistic regression identified 8 factors as important for prediction of false STEMI. Using a prediction rule derived from these factors, the area under the curve for differentiating false from true STEMI patients was 0.80 (95% CI: 0.75-0.84). Using objective standards, criteria were defined that had 95% specificity for detecting patients with an incorrect diagnosis of STEMI.

IN CONCLUSION

A prediction rule has been derived and validated in a large, racially diverse group to identify false STEMI patients with an incorrect classification rate of 5%, which is an improvement over current clinical practice. Prediction rules may be particularly useful in patients with atypical presentations in which emergent catheterization cannot be achieved rapidly or carries significant patient risk.

Risk score to predict false-positive ST-segment elevation myocardial infarction in the emergency department: a retrospective analysis

Background

The best treatment approach for ST-segment elevation myocardial infarction (STEMI) is prompt primary percutaneous coronary intervention (PCI). However, some patients show ST elevation on electrocardiography (ECG), but do not have myocardial infarction. We sought to identify the frequency of and to develop a prediction model for false-positive STEMI.

Methods

This study was conducted in the emergency departments (EDs) of two hospitals using the same critical pathway (CP) protocol to treat STEMI patients with primary PCI. The prediction model was developed in a derivation cohort and validated in internal and external validation cohorts.

Results

Of the CP-activated patients, those for whom ST elevation did not meet the ECG criteria were excluded. Among the patients with appropriate ECG patterns, the incidence of false-positive STEMI in the entire cohort was 16.3%. Independent predictors extracted from the derivation cohort for false-positive STEMI were age < 65 years (odds ratio [OR], 2.54; 95% confidence interval [CI], 1.35–4.89), no chest pain (OR, 12.04; 95% CI, 5.92–25.63), atypical chest pain (OR, 7.40; 95% CI, 3.27–17.14), no reciprocal change (OR, 4.80; 95% CI, 2.54–9.51), and concave-morphology ST elevation (OR, 14.54; 95% CI, 6.87–34.37). Based on the regression coefficients, we established a simplified risk score. In the internal and external validation cohorts, the areas under the receiver operating characteristic curves for our risk score were 0.839 (95% CI, 0.724–0.954) and 0.820 (95% CI, 0.727–0.913), respectively; the positive predictive values were 40.9% and 22.0%, respectively; and the negative predictive values were 94.9% and 96.7%, respectively.

Discussion

Our prediction model would help them make rapid decisions with better rationale.

Conclusion

We devised a model to predict false-positive STEMI. Larger-scale validation studies are needed to validate our model, and a prospective study to determine whether this model is effective in reducing improper primary PCI in actual clinical practice should be performed.

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.

Shorter Door-To-Balloon ST-Elevation Myocardial Infarction Time: Should There Be a Minimum Limit?

In ST-elevation myocardial infarction (STEMI) ischemic time is directly related to permanent myocardial damage and mortality. Therefore, it is crucial to restore myocardial perfusion rapidly. Door-to-balloon (DTB) time is defined as the duration between the arrival time of the patient to the medical facility until the time he or she is treated with percutaneous coronary intervention. Currently, DTB is the criterion that measures the quality of care provided to patients with STEMI at any given institution. It is well documented in the literature that longer DTB is associated with higher mortality; however, lowering DTB beyond current recommendations has not shown to decrease mortality rates. The current recommendations call for a DTB less than 90 minutes from the patient's first contact within the healthcare system, typically the arrival to the emergency department, to the time of the balloon inflation of the culprit coronary artery. Conversely, efforts to keep reducing DTB time may lead to unnecessary percutaneous coronary intervention (in false-positive STEMI) and delay appropriate therapy when needed, possibly missing an alternate potentially life-threatening diagnosis. In conclusion, we herein review the literature on DTB and mortality rate. We also make suggestions about ideal DTB time and hazards of shortening it beyond the recommended guidelines.

A new 4-variable formula to differentiate normal variant ST segment elevation in V2-V4 (early repolarization) from subtle left anterior descending coronary occlusion - Adding QRS amplitude of V2 improves the model

INTRODUCTION

Precordial normal variant ST elevation (NV-STE), previously often called "early repolarization," may be difficult to differentiate from subtle ischemic STE due to left anterior descending (LAD) occlusion. We previously derived and validated a logistic regression formula that was far superior to STE alone for differentiating the two entities on the ECG. The tool uses R-wave amplitude in lead V4 (RAV4), ST elevation at 60 ms after the J-point in lead V3 (STE60V3) and the computerized Bazett-corrected QT interval (QTc-B). The 3-variable formula is: 1.196 x STE60V3 + 0.059 × QTc-B - 0.326 × RAV4 with a value ≥23.4 likely to be acute myocardial infarction (AMI).

HYPOTHESIS

Adding QRS voltage in V2 (QRSV2) would improve the accuracy of the formula.

METHODS

355 consecutive cases of proven LAD occlusion were reviewed, and those that were obvious ST elevation myocardial infarction were excluded. Exclusion was based on one straight or convex ST segment in V2-V6, 1 millimeter of summed inferior ST depression, any anterior ST depression, Q-waves, "terminal QRS distortion," or any ST elevation >5 mm. The NV-STE group comprised emergency department patients with chest pain who ruled out for AMI by serial troponins, had a cardiologist ECG read of "NV-STE," and had at least 1 mm of STE in V2 and V3. R-wave amplitude in lead V4 (RAV4), ST elevation at 60 ms after the J-point in lead V3 (STE60V3) and the computerized Bazett-corrected QT interval (QTc-B) had previously been measured in all ECGs; physicians blinded to outcome then measured QRSV2 in all ECGs. A 4-variable formula was derived to more accurately classify LAD occlusion vs. NV-STE and optimize area under the curve (AUC) and compared with the previous 3-variable formula.

RESULTS

There were 143 subtle LAD occlusions and 171 NV-STE. A low QRSV2 added diagnostic utility. The derived 4-variable formula is: 0.052*QTc-B - 0.151*QRSV2 - 0.268*RV4 + 1.062*STE60V3. The 3-variable formula had an AUC of 0.9538 vs. 0.9686 for the 4-variable formula (p = 0.0092). At the same specificity as the 3-variable formula [90.6%, at which cutpoint (≥23.4), 123 of 143 MI were correctly classified for 86% sensitivity], the sensitivity of the new formula at cutpoint ≥17.75 is 90.2%, with 129/143 correctly classified MI, identifying an additional 6 cases. The cutpoint with the highest accuracy (92.0%) was at a cutoff value ≥18.2, with 88.8% sensitivity, 94.7% specificity, and a positive and negative likelihood ratio of 16.9 (95% CI: 8.9-32) and 0.12 (95% CI: 0.07-0.19). At this cutpoint, it correctly classified an additional 11 cases (289 of 315, vs. 278 of 315): 127/143 for MI (an additional 4 cases) and 162/171 for NV-STE (an additional 7 cases).

CONCLUSION

On the ECG, a 4-variable formula was derived which adds QRSV2; it differentiates subtle LAD occlusion from NV-STE better than the 3-variable formula. At a value ≥18.2, the formula (0.052*QTc-B - 0.151*QRSV2 - 0.268*RV4 + 1.062*STE60V3) was very accurate, sensitive, and specific, with excellent positive and negative likelihood ratios. This formula needs to be validated.

Sustained Performance of a "Physicianless" System of Automated Prehospital STEMI Diagnosis and Catheterization Laboratory Activation

BACKGROUND

Treatment times for primary percutaneous coronary intervention frequently exceed the recommended maximum delay. Automated "physicianless" systems of prehospital cardiac catheterization laboratory (CCL) activation show promise, but have been met with resistance over concerns regarding the potential for false positive and inappropriate activations (IAs).

METHODS

From 2010 to 2015, first responders performed electrocardiograms (ECGs) in the field for all patients with a complaint of chest pain or dyspnea. An automated machine diagnosis of "acute myocardial infarction" resulted in immediate CCL activation and direct transfer without transmission or human reinterpretation of the ECG prior to patient arrival. Any activation resulting from a nondiagnostic ECG (no ST-elevation) was deemed an IA, whereas activations resulting from ECG's compatible with ST-elevation myocardial infarction but without angiographic evidence of a coronary event were deemed false positive. In 2012, the referral algorithm was modified to exclude supraventricular tachycardia and left bundle branch block.

RESULTS

There were 155 activations in the early cohort (2010-2012; prior to algorithm modification) and 313 in the late cohort (2012-2015). Algorithm modification resulted in a 42% relative decrease in the rate of IAs (12% vs 7%; P < 0.01) without a significant effect on treatment delay.

CONCLUSIONS

A combination of prehospital automated ST-elevation myocardial infarction diagnosis and "physicianless" CCL activation is safe and effective in improving treatment delay and these results are sustainable over time. The performance of the referral algorithm in terms of IA and false positive is at least on par with systems that ensure real-time human oversight.

Frequency and factors associated with inappropriate for intervention cardiac catheterization laboratory activation

BACKGROUND

Current guidelines emphasize timely coronary intervention with a door to balloon time of ≤90min for favorable survival impact after STEMI. Efforts to achieve these targets may result in unnecessary emergent angiography for inappropriate activations.

OBJECTIVE

Evaluate the frequency, trend and factors which are significantly associated with inappropriate for intervention cardiac catheterization laboratory (CCL) activation.

METHODS

We analyzed 1764 consecutive emergent CCL activation for possible ST segment elevation myocardial infarction (STEMI) between 7/2005 and 8/2013. Inappropriate for intervention activation was defined as negative STEMI (incorrect diagnosis: insignificant coronary lesion, not requiring any intervention) and inappropriate patients (true STEMI but poor CCL candidacy).

RESULTS

Inappropriate for intervention CCL activation occurred in 317 patients (17.9%): 292 incorrect diagnosis (negative STEMI diagnosis), 25 inappropriate patients, with no difference in the frequency based on time of the day (18.6% regular hours vs. 17.6% off-hours, p=0.6). On multivariable analysis, female gender (OR 1.9 [1.2-3.0]), African American race (OR 1.9[1.3-2.7]), and prior coronary artery bypass graft surgery (OR 3.6 [2.3-5.5]) were significantly associated with incorrect diagnosis (negative STEMI diagnosis) (all p<0.005) and hyperlipidemia (OR 0.2 [0.1-0.3]), tobacco use (OR 0.2 [0.1-0.3]), and stroke/TIA (OR 0.2 [0.1-0.4]) had a significant inverse association (all p<0.001). ST Elevation with no reciprocal depression and pericarditis/myocarditis were the most common ECG finding and etiology respectively.

CONCLUSION

Inappropriate for intervention CCL activation is not uncommon and should be closely monitored to maximize resource utilization. Females, African American patients with few or no risk factors and patients presenting ST elevation but no reciprocal depression constitute a population that may require attention.

Characteristics of patients with false- ST-segment elevation myocardial infarction diagnoses

BACKGROUND

A subgroup of patients presenting with suspected ST-elevation myocardial infarction (STEMI) have no culprit lesion during coronary angiography (false-positive STEMI). Little is known about patient- and system-related factors that are associated with false-positive STEMI. We evaluated the incidence, correlates, delay, final diagnosis, and outcome of patients with false-positive STEMI.

METHODS

We studied 827 consecutive patients presenting with suspected STEMI between January 2011-September 2012.

RESULTS

A false positive STEMI activation was identified in 68 patients (8.2%). Patients with false-positive STEMI were younger (57 vs 63 year; p=0.020), less often had hypercholesterolemia (19 vs 43%; p=0.001), and had a higher heart rate (82 vs 75 bpm; p=0.014). The association between these factors and false-positive STEMI activation persisted in multivariate analysis. The duration of symptoms to call was longer in false-positive STEMI patients (128 vs 83 min; p=0.030), although this did not reach statistical significance in multivariate analysis. Final diagnosis in patients with false-positive STEMI activation was particularly from unknown origin (41%). There were no significant differences in mortality at 30 days and one year between patients with STEMI and false-positive STEMI.

CONCLUSION

The incidence of false-positive STEMI was 8.2% in patients suspected of STEMI. Patients with false-positive STEMI differ from STEMI patients in certain baseline characteristics and in patient delay. Interestingly, absence of coronary disease did not translate into better clinical outcome.

Use of quality improvement interventions and the link to performance on percutaneous intervention for acute myocardial infarction

BACKGROUND

Despite numerous calls for hospitals to employ quality improvement (QI) interventions to improve emergency department (ED) performance, their impact has not been explored in multi-site investigations.

OBJECTIVE

We investigated the association between use of QI interventions (patient flow strategies, ED electronic dashboards, and five-level triage systems) and hospital performance on receipt of percutaneous intervention (PCI) within 90 min for acute myocardial infarction patients, a publicly available quality measure.

METHODS

This was an exploratory, cross-sectional analysis of secondary data from 292 hospitals. Data were drawn from the Quality Improvement Activities Survey, the American Hospital Association's Annual Survey, and Hospital Compare. Linear regression models were used to detect differences in PCI performance scores based on whether hospitals employed one or more QI interventions.

RESULTS

Fifty-three percent of hospitals reported widespread use of patient flow strategies, 62% reported using a dashboard, and 74% reported using a five-level triage system. Time to PCI performance scores were 3.5 percentage points higher (i.e., better) for hospitals that used patient flow strategies and 6.2 percentage points higher for hospitals that used a five-level triage system. Scores were 10.4 percentage points higher at hospitals that employed two quality improvement interventions and 12.8 percentage points higher at hospitals that employed three.

CONCLUSION

Employing QI interventions was associated with better PCI scores. More research is needed to explore the direction of this relationship, but results suggest that hospitals should consider adopting patient flow strategies, electronic dashboards, and five-level triage systems to improve PCI scores.

A novel electrocardiogram parameterization algorithm and its application in myocardial infarction detection

The electrocardiogram (ECG) is a biophysical electric signal generated by the heart muscle, and is one of the major measurements of how well a heart functions. Automatic ECG analysis algorithms usually extract the geometric or frequency-domain features of the ECG signals and have already significantly facilitated automatic ECG-based cardiac disease diagnosis. We propose a novel ECG feature by fitting a given ECG signal with a 20th order polynomial function, defined as PolyECG-S. The PolyECG-S feature is almost identical to the fitted ECG curve, measured by the Akaike information criterion (AIC), and achieved a 94.4% accuracy in detecting the Myocardial Infarction (MI) on the test dataset. Currently ST segment elongation is one of the major ways to detect MI (ST-elevation myocardial infarction, STEMI). However, many ECG signals have weak or even undetectable ST segments. Since PolyECG-S does not rely on the information of ST waves, it can be used as a complementary MI detection algorithm with the STEMI strategy. Overall, our results suggest that the PolyECG-S feature may satisfactorily reconstruct the fitted ECG curve, and is complementary to the existing ECG features for automatic cardiac function analysis.

Electrocardiograhic findings resulting in inappropriate cardiac catheterization laboratory activation for ST-segment elevation myocardial infarction

BACKGROUND

Prompt reperfusion has been shown to improve outcomes in patients with acute ST-segment elevation myocardial infarction (STEMI) with a goal of culprit vessel patency in <90 minutes. This requires a coordinated approach between the emergency medical services (EMS), emergency department (ED) and interventional cardiology. The urgency of this process can contribute to inappropriate cardiac catheterization laboratory (CCL) activations.

OBJECTIVES

One of the major determinants of inappropriate activations has been misinterpretation of the electrocardiogram (ECG) in the patient with acute chest pain.

METHODS

We report the ECG findings for all CCL activations over an 18-month period after the inception of a STEMI program at our institution.

RESULTS

There were a total of 139 activations with 77 having a STEMI diagnosis confirmed and 62 activations where there was no STEMI. The inappropriate activations resulted from a combination of atypical symptoms and misinterpretation of the ECG (45% due to anterior ST-segment elevation) on patient presentation. The electrocardiographic abnormalities were particularly problematic in African-Americans with left ventricular hypertrophy.

CONCLUSIONS

In this single-center, prospective observational study, nearly half of the inappropriate STEMI activations were due to the misinterpretation of anterior ST-segment elevation and this finding was commonly seen in African-Americans with left ventricular hypertrophy.

Impact of mode of transportation on time to treatment in patients transferred for primary percutaneous coronary intervention

BACKGROUND

Patients suffering ST segment elevation myocardial infarction (STEMI) requiring transfer from a non-percutaneous coronary intervention (PCI) hospital to a PCI-capable hospital often have prolonged treatment times.

OBJECTIVE

For STEMI transfers, we changed from air to ground transportation, and carefully documented the impact on treatment times.

METHODS

This is a retrospective report between two hospitals within one STEMI system. The referring facility controls both air and ground ambulance services. After a 2-year period of air transportation with suboptimal treatment times, the referring hospital switched to ground transport. All pertinent times were carefully recorded and are reported here.

RESULTS

There were 43 patients included, approximately half were transported by air and half by ground. Comparing our early experience (air only) vs. our later experience (predominantly ground-transported patients), median door-in-door-out (DIDO) time at the first facility was 70 min vs. 35 min (p<0.001), median transport time was 20 min vs. 30 min (p<0.001), and median first medical contact to balloon time (FMC2b time) was 123 min vs. 90 min (p<0.001). After changing mode of transport, achievement of the national FMC2b time goal of <120 min rose from 47% to 92% (p<0.001).

CONCLUSIONS

We document a significantly reduced DIDO and FMC2b time after changing mode of transportation for STEMI patients transferred 30 miles for primary PCI. Utilizing ground rather than air transportation, the median FMC2b time was reduced from 123 to 90 min. We show that mode of transportation can dramatically reduce both DIDO time and FMC2b time.

Physician accuracy in interpreting potential ST-segment elevation myocardial infarction electrocardiograms

Background

With adoption of telemedicine, physicians are increasingly asked to diagnose ST‐segment elevation myocardial infarctions (STEMIs) based on electrocardiograms (ECGs) with minimal associated clinical information. We sought to determine physicians' diagnostic agreement and accuracy when interpreting potential STEMI ECGs.

Methods and Results

A cross‐sectional survey was performed consisting of 36 deidentified ECGs that had previously resulted in putative STEMI diagnoses. Emergency physicians, cardiologists, and interventional cardiologists participated in the survey. For each ECG, physicians were asked, “based on the ECG above, is there a blocked coronary artery present causing a STEMI?” The reference standard for ascertaining the STEMI diagnosis was subsequent emergent coronary arteriography. Responses were analyzed with generalized estimating equations to account for nested and repeated measures. One hundred twenty‐four physicians interpreted a total of 4392 ECGs. Among all physicians, interreader agreement (kappa) for ECG interpretation was 0.33, reflecting poor agreement. The sensitivity to identify “true” STEMIs was 65% (95% CI: 63 to 67) and the specificity was 79% (95% CI: 77 to 81). There was a 6% increase in the odds of accurate ECG interpretation for every 5 years of experience since medical school graduation (OR 1.06, 95% CI: 1.02 to 1.10, P=0.01). After adjusting for experience, there was no significant difference in the odds of accurate interpretation by specialty—Emergency Medicine (reference), General Cardiology (AOR 0.97, 95% CI: 0.79 to 1.2, P=0.80), or Interventional Cardiology physicians (AOR 1.24, 95% CI: 0.93 to 1.7, P=0.15).

Conclusions

There is significant physician disagreement in interpreting ECGs with features concerning for STEMI. Such ECGs lack the necessary sensitivity and specificity to act as a suitable “stand‐alone” diagnostic test.

Positive predictive value of clinically suspected ST-segment elevation myocardial infarction using angiographic verification

Fibrinolysis has not been used for the treatment of ST-segment elevation myocardial infarction (STEMI) in Denmark since 2005. We aimed to assess the positive predictive value of clinically suspected STEMI among consecutive patients in a real-world setting where all patients with suspected STEMI undergo acute coronary angiography. We evaluated the clinical diagnosis of consecutive patients with suspected STEMI admitted to Aarhus University Hospital between September 1, 2010, and August 31, 2011. Conclusive STEMI was defined as a patient with an identifiable culprit lesion by angiography. Of 615 patients with suspected STEMI, 483 (79%) had conclusive STEMI, and 132 (21%) did not have an identifiable culprit lesion. A higher proportion of patients with conclusive STEMI were men, whereas patients without conclusive STEMI were more likely to have diabetes mellitus (16% vs 10%; p = 0.04), left bundle branch block (24% vs 2%; p <0.001), hypertension (48% vs 36%; p = 0.01), or a history of coronary artery bypass surgery (8% vs 2%; p = 0.001). Compared with the overall 79% with conclusive STEMI, patients with left bundle branch block or a history of coronary artery bypass surgery had positive predictive values of only 26% and 41%, respectively. Our findings thus indicate that a substantial number of patients would have received fibrinolysis, without any potential benefit but with the inherent risk of bleeding complications, if acute angiography had not been an option.

Performance of a new "physician-less" automated system of prehospital ST-segment elevation myocardial infarction diagnosis and catheterization laboratory activation

The door-to-balloon times frequently exceed the recommended delay. We therefore evaluated the performance of a novel "physician-less" cardiac catheterization laboratory (CCL) activation system relying on the automated electrocardiographic diagnosis alone. From January 2010 to 2012, first responders performed electrocardiograms in the field for all patients with a complaint of chest pain or dyspnea. An automated machine diagnosis of "acute myocardial infarction" resulted in immediate CCL activation and direct transfer without human reinterpretation or transmission of the electrocardiogram. Any activation resulting from a nondiagnostic ECG (no ST-segment elevation) was deemed inappropriate and classified as resulting from either human or machine error. Of 155 activations, 136 (88%) were electrocardiographically appropriate. Of these, 128 patients had a final diagnosis of ST-segment elevation myocardial infarction. A door-to-balloon time of <90 minutes was achieved in 99%, the procedural success was high (94%), and the overall mortality was low (3%). Of the electrocardiographically appropriate activations, 8 (5%) were false-positive results. The remaining 19 activations (12%) were inappropriate. Compared with the electrocardiographically appropriate activations, those with inappropriate activations had significantly greater rates of hypertension (p = 0.0070) and known coronary artery disease (p = 0.0008) and higher presenting heart rates (p <0.0001). The causes for inappropriate activation were approximately evenly split between human and machine error. In conclusion, a combination of prehospital automated ST-segment elevation myocardial infarction diagnosis and "physician-less" CCL activation was safe and effective in ensuring target door-to-balloon times in virtually all patients and resulted in an acceptable rate of inappropriate CCL activation.

Impact of the prehospital activation strategy in patients with ST-elevation myocardial infarction undergoing primary percutaneous revascularization: a single center community hospital experience

The strategy of prehospital activation by the emergency medical system (EMS) in patients with ST-elevation myocardial infarction (STEMI) has been poorly adopted among the US hospitals that currently offer 24/7 primary percutaneous coronary intervention. In this study, we report a single center experience after the implementation of this strategy. From 2008 to 2011, we identified a total 188 STEMI patients (age 65 ± 15 years) presenting via EMS for primary percutaneous coronary intervention. Of these, 112 (59.6%) underwent prehospital activation (EMS group), whereas the remaining 76 (40.4%) underwent emergency department activation [emergency department (ED) group]. Baseline demographic characteristics were similar between both groups. The overall median door-to-balloon (DTB) time was 49 ± 14 minutes. Patients undergoing prehospital activation had on average significantly lower overall DTB times (EMS 44 ± 11 minutes vs. ED 57 ± 15 minutes; P < 0.001). Concordantly, DTB times <60 minutes were much more commonly achieved with this strategy (EMS 95.5% vs. ED 64.5%; P < 0.001). Fallouts beyond the recommended 90-minute DTB time were seen among ED patients only. No difference in in-hospital death (EMS 5.4% vs. ED 6.6%; P = 0.75) or cumulative 30-day mortality (EMS 6.3% vs. ED 7.9%; P = 0.68) was observed between both groups. However, on average, EMS patients had higher postinfarct left ventricular ejection fraction (EMS 48 ± 9.5% vs. ED 39 ± 14.6%; P = 0.004). Differences in DTB time and left ventricular ejection fraction remained significant after adjusting for differences in baseline characteristics. In conclusion, the prehospital activation strategy is largely effective and should be systematically adopted in the treatment scheme of STEMI patients to lower mechanical reperfusion times and reduce the potential for untoward clinical outcomes.

Setting Up a Population-Based Program to Optimize ST-Segment Elevation Myocardial Infarction Care

The development of ST-segment elevation myocardial infarction (STEMI) systems of care at the city, region, or nation levels has not only improved the speed of reperfusion but also enhanced the reach of primary angioplasty to areas far from percutaneous coronary intervention (PCI) centers. Setting up a STEMI system of care is a sophisticated process that requires a solid PCI hospital and emergency medical services infrastructure, disciplined collaboration, and a focus on outcomes measurement and continuous quality improvement. This article reviews the accumulated evidence supporting the development of STEMI systems of care and offers practical insights into this process.