ST-segment instability preceding simultaneous cardiac arrest and AMI in a patient undergoing continuous 12-lead ECG monitoring

Primary percutaneous coronary intervention is appropriate in transient ST-elevation myocardial infarction

INTRODUCTION

Reperfusion therapy by primary percutaneous coronary intervention (PPCI) is generally indicated in patients suffering from acute myocardial infarction (MI) with ST-segment elevation (STEMI). Prior to hospital admission, full ST-segment resolution (fSTR) may occur. Optimal management of such patients with transient STEMI (TSTEMI) is potentially challenging. Our aim was to evaluate the hypothesis that in TSTEMI patients, patency of infarct related artery (IRA) is achieved before PPCI, and to compare the outcome of TSTEMI and STEMI patients during a prolonged follow-up.

MATERIAL AND METHODS

Three hundred consecutive adult STEMI patients were referred to catheterization laboratory. In all patients, standard 12 lead ECGs were obtained both at the time of the first medical contact, and on catheterization laboratory admission.

RESULTS

TSTEMI occurred in 20 patients (6.7%). Despite fSTR (isoelectric ST segment), occluded IRA was found in 5 of these patients (25%). Pre-PPCI TIMI flow grade 2 was found in 6 TSTEMI patients (30%). Troponin T value at 24 h after symptom onset was lower in the TSTEMI group (1.8±2.5 mg/L vs. 3.6±3.5 mg/L, P=0.008). These patients also had a lower value of brain natriuretic peptide (156.3±119.5 ng/L vs. 438.5±429.0 ng/L, P<0.001) and higher left ventricular ejection fraction (59.9±6.3% vs. 51.6±10.2%, P<0.001). All patients were followed for a median of 5.6 years during which the overall survival did not differ between the TSTEMI and STEMI groups.

CONCLUSION

Primary PCI is strongly recommended in TSTEMI patients because of a relatively high incidence of occluded infarct related arteries. The rate of patients with TSTEMI is relatively low.

Prevalence and interventional outcomes of patients with resolution of ST-segment elevation between prehospital and in-hospital ECG

OBJECTIVE

To determine the prevalence and significance of ST-segment elevation resolution between prehospital and first hospital ECG.

METHODS

We examined consecutive prehospital ECGs transmitted to a single medical command center in southwestern Pennsylvania between January 1, 2009 and December 31, 2011. We included ECG cases with ST-segment elevation myocardial infarction (STEMI) and excluded cases with incomplete prehospital and/or hospital data. Our primary outcome was ST-segment resolution (STR), defined by cases no longer meeting STEMI criteria on the first in-hospital ECG. Primary variables of interest included prehospital vital signs and treatment, cardiac catheterization findings, and time intervals for diagnostics and treatment. Analysis included t-tests for continuous variables and chi-squared analysis for categorical variables.

RESULTS

We reviewed 24,197 prehospital ECGs and identified 293 cases of prehospital STEMI. Complete hospital and prehospital records were available for 83 cases (28%). Analyzed cohort was an average 62 years old and the majority were male (67%), with a primary complaint of chest pain (93%). STR occurred in 18 cases (22%, CI 14-32%). There were no differences between STR and non-STR cases in prehospital vital signs or treatments. 95% of patients underwent cardiac catheterization with a mean door-to-needle time of 57 minutes (interquartile range 43-71). Comparing STR and non-STR cases, significant lesions (≥50%) were found in 94 and 97% of patients (p = 0.6), and subtotal or total lesions (≥95%) were found in 63 and 85% (p = 0.1), respectively.

CONCLUSIONS

We found that ST-segment resolution occurred prior to catheterization in 1 of 5 patients with prehospital STEMI, emphasizing the necessity of prehospital ECG in risk stratification of patients with suspected coronary disease. Coronary lesions and intervention rates did not differ between STR and non-STR, suggesting that catheterization is warranted even when STEMI criteria are no longer met in-hospital.

Management strategies for patients with low-risk chest pain in the emergency department

OPINION STATEMENT

There is abundant evidence to guide the management of chest pain patients with a confirmed or reasonably suspected diagnosis of acute coronary syndrome (ACS). But when it comes to the low-risk chest pain patient in the emergency department, there is limited evidence to support one approach over another. As a result, the evaluation of low-risk chest pain represents a distinct challenge for the emergency physician. Missing a diagnosis of ACS is certainly undesirable. However, the overuse of technology can result in misleading test results in populations with a low incidence of coronary disease. In this article, we dispel several myths surrounding low-risk chest pain and put forward a number of common-sense recommendations. We endorse taking a focused but thorough chest pain history; encourage the use of serial electrocardiogram, particularly for patients with ongoing or changing symptoms; comment on the interpretation of cardiac biomarkers in the era of highly sensitive troponin assays, drawing a distinction between myocardial injury and myocardial infarction; discuss the role of coronary computed tomography angiography as a test for coronary artery disease, rather than for ACS; and caution against the reflexive use of provocative testing in low-risk chest pain patients.

Continuous 12-lead electrocardiographic monitoring in an emergency department chest pain unit: an assessment of potential clinical effect

STUDY OBJECTIVES

Continuous 12-lead serial ECG monitoring has been proposed to assist in the evaluation of patients with acute coronary syndrome and nondiagnostic ECG in an emergency department chest pain unit. However, the ability of serial ECG to detect acute coronary syndrome and its benefit in addition to a standard protocol has not been established. We evaluate the ability of continuous 12-lead ECG to detect acute coronary syndrome, assess the incremental benefit of the serial ECG in association with a set protocol in an ED chest pain unit, and evaluate whether serial ECG changes could be considered as prognostic factors.

METHODS

Patients who met Agency for Health Care Policy and Research guidelines for intermediate risk for short-term cardiovascular event unstable angina were prospectively studied in the chest pain unit. Patients were monitored with the Mortara Instruments ELI 100 STM continuous 12-lead ECG system with ST-segment analysis. ST-segment changes of greater than 100 microV in 2 or more contiguous leads or greater than 200 microV in 1 lead were considered positive. Data were compared with serial serum cardiac markers, cardiac function study results, angiographic results, and 30-day outcome results.

RESULTS

One hundred nineteen patients had serial ECG applied. The median duration of monitoring was 4.2 hours. Forty patients were given a diagnosis of acute coronary syndrome. Chest pain unit protocol detected 52 patients, and 23 were given a diagnosis of acute coronary syndrome (sensitivity 58%; specificity 63%). Sixteen patients had ST-segment changes of greater than 100 microV or greater than 200 microV, and 9 were given a diagnosis of acute coronary syndrome. The addition of the serial ECG to the chest pain unit protocol increased the sensitivity to 65% and decreased the specificity to 58%. Two patients with ST-segment changes but none without ST-segment changes had an adverse cardiac event, yielding a sensitivity of 100% and a specificity of 88%.

CONCLUSION

Serial ECG is of limited value in the diagnostic evaluation of intermediate-risk patients managed in the chest pain unit with a standard protocol. However, when ST-segment changes are present, they indicate an increased likelihood for an adverse cardiac event.

Usefulness of automated serial 12-lead ECG monitoring during the initial emergency department evaluation of patients with chest pain

STUDY OBJECTIVE

To determine whether the use of automated serial 12-lead ECG monitoring (SECG) is more sensitive and specific than the initial 12-lead ECG in the detection of injury and ischemia in patients with acute coronary syndromes (ACS) during the initial ED evaluation of patients with chest pain.

METHODS

A prospective observational study was performed in 1,000 patients with chest pain who were admitted to a university teaching hospital and who underwent continuous ST-segment monitoring with SECG during the initial ED evaluation. The initial ECG was obtained on presentation, and SECG readings were obtained at least every 20 minutes during the ED evaluation. Diagnostic abnormalities on the initial ECG were defined as injury or ischemia. Diagnostic changes on SECG were defined as evolving injury, evolving ischemia, new injury, or new ischemia. ACS was defined as acute myocardial infarction (AMI), recent myocardial infarction or unstable angina.

RESULTS

A diagnostic SECG was more sensitive than a diagnostic initial ECG for detection of AMI (68.1% versus 55.4%; P < .0001) and ACS (34.2% versus 27.5%; P < .0001). A diagnostic SECG was more specific than a diagnostic initial ECG for detection of ACS (99.4% versus 97.1%; P < .01). SECG detected injury in an additional 16.2% of AMI patients compared with the initial ECG (61.8% versus 45.6%; P < .0001; 95% confidence interval for difference of proportions, 10.9% to 21.4%).

CONCLUSION

SECG during the initial ED evaluation is more sensitive and more specific than the initial ECG in the identification of ACS. Patients with a diagnostic SECG need intensive antiischemic therapy, evaluation for reperfusion therapy, and admission to an ICU.

ECG diagnosis of acute myocardial infarction in the presence of left bundle-branch block in patients undergoing continuous ECG monitoring

It is common knowledge that the ECG diagnosis of completed myocardial infarction in the presence of left bundle-branch block (LBBB) is extremely difficult and often impossible. More than 50 rules have been proposed as criteria for interpreting Q-wave equivalents superimposed on the QRS complex in the presence of LBBB. However, because of misinterpretation of the available literature, physicians frequently recommend that patients with chest pain in the presence of LBBB receive thrombolytic therapy or urgent coronary arteriography on the basis of the assumption that acute injury and ischemia cannot be interpreted in the presence of LBBB. Unfortunately, many physicians fail to realize that although completed infarction is difficult to confirm in the presence of LBBB, ongoing ischemia and injury can be detected in the presence of LBBB and may be seen as often as they are in the presence of normal cardiac conduction. A deflection of the J point (and ST segment) in the direction of the major QRS complex or an elevation of the ST segment of more than 7 to 8 mm opposite the direction of the major QRS complex has been demonstrated to have a sensitivity of more than 50% in detecting acute injury, with a specificity of more than 90%. During the first half of an ongoing prospective study of the use of continuous 12-lead ECG monitoring in the emergency department, we encountered five patients with final diagnoses of acute myocardial infarction in the presence of LBBB who demonstrated significant ECG changes while undergoing continuous ST-segment monitoring with frequent serial ECGs. The five different locations of the infarcts in these five patients were posterior, posterolateral, inferior, anterior, and anterolateral. We present these patients' cases to demonstrate the ECG characteristics of acute injury in the presence of LBBB.

Instability of ST segments in the early stages of acute myocardial infarction in patients undergoing continuous 12-lead ECG monitoring

Many patients presenting to the emergency department with suspected acute myocardial infarction (AMI) have an initial 12-lead electrocardiogram (ECG) nondiagnostic for acute injury and thus do not meet any accepted ECG criteria for thrombolytic therapy. Early studies in the use of intracoronary thrombolytic therapy documented that cyclic variations in ST segment magnitudes between normalcy and injury are common during the early phase of AMI and correspond to spontaneous intermittent coronary opening and reocclusion. The reliance on a single ECG to diagnose AMI may mean that many patients with AMI are missed if the initial ECG is obtained during a window of ST segment normalcy. We present 3 patients with AMI who underwent continuous 12-lead ST segment monitoring with frequent serial ECGs whose ST segments periodically normalized during the acute injury phase. We believe continuous 12-lead ST segment monitoring with frequent serial ECGs can aid the physician in identifying patients with AMI who may benefit from thrombolytic therapy and other urgent revascularization techniques.