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

Whole-Genome Approach Discovers Novel Genetic and Nongenetic Variance Components Modulated by Lifestyle for Cardiovascular Health

Background

Both genetic and nongenetic factors can predispose individuals to cardiovascular risk. Finding ways to alter these predispositions is important for cardiovascular disease prevention.

Methods and Results

We used a novel whole‐genome approach to estimate the genetic and nongenetic effects on—and hence their predispositions to—cardiovascular risk and determined whether they vary with respect to lifestyle factors such as physical activity, smoking, alcohol consumption, and dietary intake. We performed analyses on the ARIC (Atherosclerosis Risk in Communities) Study (N=6896–7180) and validated findings using the UKBB (UK Biobank, N=14 076–34 538). Lifestyle modulation was evident for many cardiovascular traits such as body mass index and resting heart rate. For example, alcohol consumption modulated both genetic and nongenetic effects on body mass index, whereas smoking modulated nongenetic effects on heart rate, pulse pressure, and white blood cell count. We also stratified individuals according to estimated genetic and nongenetic effects that are modulated by lifestyle factors and showed distinct phenotype–lifestyle relationships across the stratified groups. Finally, we showed that neglecting lifestyle modulations of cardiovascular traits would on average reduce single nucleotide polymorphism heritability estimates of these traits by a small yet significant amount, primarily owing to the overestimation of residual variance.

Conclusions

Lifestyle changes are relevant to cardiovascular disease prevention. Individual differences in the genetic and nongenetic effects that are modulated by lifestyle factors, as shown by the stratified group analyses, implies a need for personalized lifestyle interventions. In addition, single nucleotide polymorphism–based heritability of cardiovascular traits without accounting for lifestyle modulations could be underestimated.

Detection of STEMI Using Prehospital Serial 12-Lead Electrocardiograms

OBJECTIVE

Repeated or serial 12-lead electrocardiograms (ECGs) in the prehospital setting may improve management of patients with subtle ST-segment elevation (STE) or with a ST-segment elevation myocardial infarction (STEMI) that evolves over time. However, there is a minimal amount of scientific evidence available to support the clinical utility of this method. Our objective was to evaluate the use of serial 12-lead ECGs to detect STEMI in patients during transport in a Canadian emergency medical services (EMS) jurisdiction.

METHODS

We performed a retrospective study of suspected STEMI patients transported by EMS in the Chaudière-Appalaches region (Québec, Canada) between August 2006 and December 2013. Patients were monitored by a serial 12-lead ECG system where an averaged ECG was transmitted every 2 minutes. Following review by an emergency physician, ECGs were grouped as having either a persistent STE or a dynamic STE that evolved over time.

RESULTS

A total of 754 suspected STEMI patients were transported by EMS during the study period. Of these, 728 patients met eligibility criteria and were included in the analysis. A persistent STE was observed in 84.3% (614/728) of patients, while the remaining 15.7% (114/728) had a dynamic STE. Among those with dynamic STE, 11.1% (81/728) had 1 ST-segment change (41 no-STEMI to STEMI; 40 STEMI to no-STEMI) and 4.5% (33/728) had ≥ 2 ST-segment changes (17 no-STEMI to STEMI; 16 STEMI to no-STEMI). Overall, in 8.0% (58/728) of the cohort, STEMI was identified on a subsequent ECG following an initial no-STEMI ECG.

CONCLUSIONS

Through recognition of transient ST-segment changes during transport via the prehospital serial 12-lead ECG system, STEMI was identified in 8% of suspected STEMI patients who had an initial no-STEMI ECG. Key words: electrocardiography; emergency medical services; ST-elevation myocardial infarction; prehospital dynamic ECG.

The Value of Continuous ST-Segment Monitoring in the Emergency Department

Practice standards for electrocardiographic monitoring recommend continuous ST-segment monitoring (C-STM) in patients presenting to the emergency department (ED) with signs and/or symptoms of acute coronary syndrome (ACS), but few studies have evaluated its use in the ED. We compared time to diagnosis and 30-day adverse events before and after implementation of C-STM. We also evaluated the diagnostic accuracy of C-STM in detecting ischemia and infarction. We prospectively studied 163 adults (preintervention: n = 78; intervention: n = 85) in a single ED and stratified them into low (n = 51), intermediate (n = 100), or high (n = 12) risk using History, ECG, Age, Risk factors, and Troponin (HEART) scores. The principal investigator monitored participants, activating C-STM on bedside monitors in the intervention phase. We used likelihood ratios (LRs) as the measure of diagnostic accuracy. Overall, 9% of participants were diagnosed with ACS. Median time to diagnosis did not differ before and after implementation of C-STM (5.55 vs. 5.98 hr; p = 0.43). In risk-stratified analyses, no significant pre-/postdifference in time to diagnosis was found in low-, intermediate-, or high-risk participants. There was no difference in the rate of 30-day adverse events before versus after C-STM implementation (11.5% vs. 10.6%; p = 0.85). The +LR and -LR of C-STM for ischemia were 24.0 (95% confidence interval [CI]: 1.4, 412.0) and 0.3 (95% CI: 0.02, 2.9), respectively, and for infarction were 13.7 (95% CI: 1.7, 112.3) and 0.7 (95% CI: 0.3, 1.5), respectively. Use of C-STM did not provide added diagnostic benefit for patients with signs and/or symptoms of myocardial ischemia in the ED.

The Role of Nurses in a Chest Pain Unit

The chest pain unit (CPU) provides a service for patients at moderate-to-low risk for acute coronary syndrome (ACS). Although the number of CPUs has continued to grow worldwide, little has been written on the specific role and contribution of nursing in CPUs. The stay of patients in the CPU can be divided into six stages: triage, diagnosis, treatment, observation/monitoring, discharge, and follow-up. CPU nurses are in a unique position to promote evidence-based practice during all of these stages. Deeper insight into the unique role of nurses in CPUs will promote understanding of what type of knowledge, skills, and attitudes are required to provide the services that will contribute to improved quality of care for chest pain patients.

Chest Pain in Emergency Department Patients: If the Pain is Relieved by Nitroglycerin, is it More Likely to be Cardiac Chest Pain?

Introduction:

It is often believed that chest pain relieved by nitroglycerin is indicative of coronary artery disease origin.

Objective:

To determine if relief of chest pain with nitroglycerin can be used as a diagnostic test to help differentiate cardiac chest pain and non-cardiac chest pain.

Design:

Prospective observational cohort study with a 4-week follow-up of patients enrolled.

Setting:

Academic tertiary care hospital, with 60 000 visits/year.

Inclusion criteria:

Adult patients presenting to the emergency department with active chest pain who received nitroglycerin and were admitted for chest pain.

Exclusion criteria:

Patients with acute myocardial infarction diagnosed after obtaining an ECG, patients whose chest pain could not be quantified, those for whom no cardiac work-up was done, or those who received emergent cardiac catheterization.

Results:

270 patients were enrolled. Nitroglycerin relieved chest pain in 66% of the subjects. The diagnostic sensitivity of nitroglycerin to determine cardiac chest pain was 72% (64%–80%), and the specificity was 37% (34%–41%). The positive likelihood ratio for having coronary artery disease if nitroglycerin relieved chest pain was 1.1 (0.96–1.34). Telephone follow-up at 4 weeks was performed, with a 95% follow-up rate.

Conclusions:

Relief of chest pain with nitroglycerin is not a reliable diagnostic test and does not distinguish between cardiac and non-cardiac chest pain.

Chest pain unit concept: rationale and diagnostic strategies

Each year in the United States, over 8 million patients present to the emergency department(ED) with complaints of chest discomfort or other symptoms consistent with possible acute coronary syndrome (ACS). While over half of these patients are typically admitted for further diagnostic evaluation, fewer than 20% are diagnosed with ACS. With hospital beds and inpatient resources scarce, these admissions can be avoided by evaluating low- to moderate-risk patients in chest pain units. This large, undifferentiated patient population represents a potential high-risk group for emergency physicians requiring a systematic approach and specific ED resources. This evaluation is required to appropriately determine if a patient is safe to be discharged home with outpatient follow-up versus requiring admission to the hospital for monitoring and further testing.

Risk stratification in acute coronary syndromes--does the TIMI risk score work in unselected cases?

BACKGROUND

Management of patients with an acute coronary syndrome (ACS) requires accurate risk stratification to guide appropriate therapy.

AIM

To assess the utility of the TIMI risk score in stratifying patients with possible ACS in routine clinical practice.

DESIGN

Prospective observational study.

METHODS

We recruited 869 consecutive patients with a diagnosis of possible ACS attending the acute medical receiving unit of a district general hospital. The main outcome measures were recurrent myocardial infarction, urgent revascularization, and all-cause mortality. TIMI risk score was calculated for each patient, and each was also assigned a risk group based on electrocardiogram (ECG) changes and troponin levels only. After follow-up, Cox univariate and multivariate regression was used to evaluate the influence of potential risk factors on duration of event-free survival, and likelihood ratio tests to assess the fit of the models.

RESULTS

Increasing TIMI risk score was associated with increased risk of events (p<0.001), as was higher risk group from ECG plus troponin stratification (p<0.001). The likelihood ratio comparison favoured the TIMI risk score (difference 13.910, 5 degrees of freedom, p = 0.016).

DISCUSSION

The TIMI risk score is a valid tool for risk stratification in unselected cases with possible acute coronary syndrome. It is superior to ECG changes and troponin alone, although this simpler method also achieves good risk stratification.

Which diagnostic tests are most useful in a chest pain unit protocol?

BACKGROUND

The chest pain unit (CPU) provides rapid diagnostic assessment for patients with acute, undifferentiated chest pain, using a combination of electrocardiographic (ECG) recording, biochemical markers and provocative cardiac testing. We aimed to identify which elements of a CPU protocol were most diagnostically and prognostically useful.

METHODS

The Northern General Hospital CPU uses 2-6 hours of serial ECG/ST segment monitoring, CK-MB(mass) on arrival and at least two hours later, troponin T at least six hours after worst pain and exercise treadmill testing. Data were prospectively collected over an eighteen-month period from patients managed on the CPU. Patients discharged after CPU assessment were invited to attend a follow-up appointment 72 hours later for ECG and troponin T measurement. Hospital records of all patients were reviewed to identify adverse cardiac events over the subsequent six months. Diagnostic accuracy of each test was estimated by calculating sensitivity and specificity for: 1) acute coronary syndrome (ACS) with clinical myocardial infarction and 2) ACS with myocyte necrosis. Prognostic value was estimated by calculating the relative risk of an adverse cardiac event following a positive result.

RESULTS

Of the 706 patients, 30 (4.2%) were diagnosed as ACS with myocardial infarction, 30 (4.2%) as ACS with myocyte necrosis, and 32 (4.5%) suffered an adverse cardiac event. Sensitivities for ACS with myocardial infarction and myocyte necrosis respectively were: serial ECG/ST segment monitoring 33% and 23%; CK-MB(mass) 96% and 63%; troponin T (using 0.03 ng/ml threshold) 96% and 90%. The only test that added useful prognostic information was exercise treadmill testing (relative risk 6 for cardiac death, non-fatal myocardial infarction or arrhythmia over six months).

CONCLUSION

Serial ECG/ST monitoring, as used in our protocol, adds little diagnostic or prognostic value in patients with a normal or non-diagnostic initial ECG. CK-MB(mass) can rule out ACS with clinical myocardial infarction but not myocyte necrosis(defined as a troponin elevation without myocardial infarction). Using a low threshold for positivity for troponin T improves sensitivity of this test for myocardial infarction and myocardial necrosis. Exercise treadmill testing predicts subsequent adverse cardiac events.