ECGs Are Not Created Equal

Short Attention Span Summary

ECGs are not created equal
Looking purely at 6 ECG criteria, these authors looked at risk of 30-day major adverse coronary events (MACE), type 1 MI, type 2 MI, and death at 1 year.  Risk of MACE and type 1 MI increased with each ECG criterion, but type 2 MI didn't correlate as well.  Quoting straight from the article, the 6 criteria were:

  1. Normal - No possible evidence for ischemia.  30-day MACE, 5%
  2. Nonspecific ST-T-wave changes - Accepted deviation from the norm, with the lowest likelihood of ischemia (e.g., inverted T-wave axis in III or V1). 30-day MACE, 13.6%
  3. Abnormal but not diagnostic of ischemia - Prolonged PR, QRS, QTc intervals, bundle branch blocks, left ventricular hypertrophy with strain. 30-day MACE, 13%
  4. Ischemia or previous infarction known to be old - ST-segment depression of at least 0.5 mm (0.05 mV) in two or more contiguous leads (includes reciprocal changes), T-wave inversion of at least 1 mm (0.1 mV) including inverted T-waves that are not indicative of acute MI, or Q-waves > 30 ms in duration with evidence that this is preexisting on previous ECG. 30-day MACE, 24.7%
  5. Ischemia or previous infarction not known to be old - ST-segment depression of at least 0.5 mm (0.05 mV) in two or more contiguous leads (includes reciprocal changes), T-wave inversion of at least 1 mm (0.1 mV) including inverted T-waves that are not indicative of AMI, or Q-waves > 30 ms in duration with evidence that this is not preexisting on previous ECG. 30-day MACE, 55.3%
  6. Consistent with AMI - New or presumed new ST-segment elevation at the J-point in two or more contiguous leads with the cutoff points greater than or equal to 0.2 mV in leads V1, V2, or V3 or ≥0.1 mV in other leads or new left bundle branch block (LBBB) ST-elevation or LBBB. 30-day MACE, 66.7%

Spoon Feed
ECG is never used alone for cardiac risk stratification, but some ECG findings are more concerning than others.  For example, a patient with chest pain and new ST depression in two contiguous leads (i.e. criterion 5) would have >50% probability of MACE in 30 days based on the ECG alone.  Don't send this one home!  For more on cardiac risk stratification, see Amal Mattu's guide to low risk chest pain on Evidence Care.


Abstract

Acad Emerg Med. 2017 Mar;24(3):344-352. doi: 10.1111/acem.13123.

The Association of Electrocardiographic Abnormalities and Acute Coronary Syndrome in Emergency Patients With Chest Pain.

Knowlman T1, Greenslade JH1,2,3, Parsonage W1,4, Hawkins T2,3, Ruane L1,2,3,5, Martin P4, Prasad S1,5, Lancini D1,4, Cullen L1.

Author information:

1 School of Medicine, University of Queensland, Brisbane, Queensland.

2 School of Public Health, Queensland University of Technology, Brisbane, Queensland.

3 Department of Emergency Medicine, Royal Brisbane and Women's Hospital, Brisbane, Queensland.

4 Department of Cardiology, Royal Brisbane and Women's Hospital, Brisbane, Queensland.

5 Sydney Medical School, University of Sydney, Sydney, New South Wales, Australia.

Abstract

OBJECTIVES:

The electrocardiograph (ECG) is an essential tool in initial management and risk stratification of patients with suspected acute coronary syndrome (ACS). A six-point reporting criterion has been proposed to facilitate standardized clinical assessment of patients presenting to the emergency department (ED) with suspected ACS. We set out to evaluate the efficacy of these criteria in identifying patients with major adverse cardiac events (MACE), Type 1 myocardial infarction (T1MI), Type 2 myocardial infarction (T2MI), and 1-year mortality in a cohort of emergency patients with chest pain.

METHODS:

This was an analysis of data from 2,349 patients who presented to the ED with chest pain between 2008 and 2013. Data were collected as part of two prospective trials. ECGs were recorded at presentation and categorized according to the six-point criteria by local cardiologists blinded to all clinical information. The primary outcome was 30-day MACE, including T1MI, T2MI, unstable angina pectoris, revascularization, and 30-day mortality. The outcome was adjudicated by cardiologists on the basis of all clinical information and test results. Likelihood ratios and odds ratios for 30-day MACE were reported for each ECG category.

RESULTS:

Major adverse cardiac events were diagnosed in 264 (11.3%) patients. Increasing ischemic abnormalities in ECGs, as categorized by the standardized reporting criteria, were associated with increasing rates of MACE. Within 30 days, T1MI occurred in 148 (6.3%) patients and T2MI occurred in 59 (2.5%) patients. Risk for T1MI increased with higher classification of ECG abnormalities. T2MI rates were highest in patients with ECGs of nonspecific changes.

CONCLUSIONS:

The rates of MACE, T1MI, and 1-year death can be stratified according to standardized ECG criteria in patients presenting to the ED with chest pain. The ECG findings in patients with T2MI are variable, and the ECG is less helpful in defining risk in this group.

© 2016 by the Society for Academic Emergency Medicine.

PMID: 27797440