The ECG in Chest Pain

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STTChanges
Introduction

  • A common indication for an ECG is in a patient presenting with acute chest pain or features suspicious for an acute coronary syndrome
  • The most important diagnosis to identify quickly is an acute ST elevation myocardial infarction (STEMI) because of its significant mortality rate and that urgent revascularisation may be indicated
  • Any ST segment and T wave changes in a contiguous or geographical location of the heart may be consistent with myocardial ischaemia or infarction and should be considered carefully
  • Be aware that acute coronary occlusion may be evolving or threatening despite normal ST/T changes
  • A normal ECG does not rule out ischaemia or infarction.  The nature of the pain, age and presence of risk factors and serum troponin also help risk stratify.
  • Similarly ST/T changes can be seen in other acute and non-acute pathology and the rest of the ECG, clinical context and previous ECGs can help interpretation
  • A critical therapeutic error occurs when thrombolysis or anticoagulation is administered by mistaking the ECG changes and chest pain of acute pericarditis or thoracic aortic aneurysm as a MI.  Review the history carefully and consider additional testing before  treatment
  • The most frequent mistake by JMOs is to misinterpret the ST/T changes of bundle branch block, left ventricular hypertrophy and digoxin use as a myocardial injury pattern

 
CLASSIC STEMI PATTERNS

  ST/T changes Other changes Notes
ST elevation myocardial infarction (STEMI) Elevation in contiguous leads +/- ‘Reciprocal’ ST depression in other leads

STEMI equivalents (High Risk)

Wellen’s criteria (severe LAD disease) Normal or mild ST elevation in contiguous leads
Biphasic or deep T waves inversion
History of resolved cardiac pain
De Winter Waves (acute LAD occlusion) Up-sloping ST depression and peaked T waves in antero-septal leads
Left Main Coronary Occlusion Widespread ST depression especially lateral and high lateral leads
ST elevation AVR
Hyperacute MI Hyper-acute peaked T waves in contiguous leads Repeat ECG after 10 minutes to identify evolving ECG changes
Posterior myocardial infarction ST depression in antero-septal leads Dominant R wave and upright T waves in same leads
Posterior leads show ST elevation
Associated with hypotension if RV involvement

Other STEMI

Thoracic aortic dissection and RCA Occlusion ST elevation in inferior leads Sudden tearing chest pain radiating to inter-scapular region
Do not thrombolyse

Myocardial ischaemia (intermediate risk)

Prinzmetal’s angina (coronary vasospassm) Same as STEMI but spontaneously resolves Normal biomarkers
Myocardial ischaemia (pseudonormalisation) Previously inverted T waves of old MI become upright during acute ischaemia Check old ECG
Non-STEMI (NSTEMI)
Or Unstable Angina
Depression in contiguous leads

Non-specific  (low risk)

Intermediate risk Downsloping ST segments or T wave flattening in contiguous leads

ACS/STEMI mimics seen in acute pathology
Other acute cardiac pathology
Acute Non-cardiac pathology
ACS/STEMI mimics
Conduction abnormalities
Pre-existing structural cardiac disease
Normal variants
 

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