OzEMedicine - Wiki for Australian Emergency Medicine Doctors

see also:

• The basics of reading an ECG
• patterns of ECGs
• ECG diagnosis of AMI
• EMRAP TV Episode 53: 11 causes of ST Elevation

• a common dilemma on a daily basis in adult ED's is the patient with an ECG with ST elevation - does this patient warrant urgent angioplasty or thrombolysis, or is it non-ischaemic in nature?

• one needs to have pattern recognition of the features of potentially fatal hyperkalaemia which include ST elevation, wide QRS, etc.

• look for a pacing spike in any broad complex rhythm - ST elevation is usually seen in inferior and precordial leads
• look for P waves to help exclude a ventricular rhythm and help confirm it is a LBBB
• a presumed new LBBB in the context of ischaemic chest pain is usually an indicator in itself for urgent angioplasty or thrombolysis.
• a previously documented LBBB makes Mx of possible AMI and the interpretation of ST segments difficult - see Left Bundle Branch Block (LBBB) for possible solution whilst awaiting cardiac enzyme studies
• not much point continuing on in this algorithm here!

• the ST elevation of Right Bundle Branch Block (RBBB) is usually in lateral leads (rule of discordance - ST/Twave is directed opposite to terminal portion of QRS in BBB)
• one should consider the rare but potentially fatal Brugada syndrome if there is ST elevation in V1-2 as well in a young person.
• consider pulmonary embolism (PE) or infarct in new onset RBBB
• RBBB does not disguise ECG diagnosis of AMI so continue on…

• NB. for ST elevation to be regarded sufficient to embark on reperfusion in AMI, it must be consistent with that of an AMI and must satisfy either:
  • presumed new ST elevation of 1mm or more in two or more contiguous limb leads, or,
  • presumed new ST elevation of 2mm or more in two or more contiguous precordial leads
• if it does not satisfy the above and the patient presents with possible ischaemic chest pain, then repeat ECG's looking for dynamic changes.

• think about life threatening left main coronary artery occlusion, proximal left anterior descending artery (LAD) occlusion or severe multi-vessel disease
• see http://lifeinthefastlane.com/ecg-exigency-014/

• if ST elevation in V1 but ST normal or depressed in V2, look closely at inferior leads as this could be a RV infarct - consider doing right precordial leads
• if ST elevation only in V1 and V2, then if R:S amplitude ratio at least 1 then consider a posterior infarct - consider doing V7-9 leads
• if ST elevation also in aVR and it is greater there than in V1, then consider infarct due to occlusion of left main coronary artery
• if complete or incomplete RBBB (ie. RSR' pattern) then consider Brugada syndrome or infarct
• if R waves with T wave inversion, consider potentially lethal Wellen's syndrome (critical proximal LAD stenosis)
• if tall R waves, elevated J point, < 50yrs old, no reciprocal ST depression with no change over time, then consider benign early repolarisation
• if deep Q waves with ST elevation then consider either:
  • LVH
    • ST elevation mainly V1-3 proportional with deep S waves
    • ST depression in lateral leads proportional with positive QRS
    • if ST changes out of proportion to QRS changes or convex then consider infarct
  • LV aneurysm
    • ratio of T wave amplitude to QRS amplitude in V1-4 is low (<0.2)
    • QS or Qr waves, relatively low ST elevation, some T inversion
  • delayed presentation of (antero)septal MI
• none of the features above, then strongly consider (antero)septal MI, particularly if temporal, convex and with reciprocal ST depression.
• other conditions which much less commonly cause right precordial ST elevation:
  • pericarditis but usually concave and ST elevation in inf/lat. leads as well
  • CNS events such as stroke (CVA) or subarachnoid haemorrhage (SAH)
    • 10-25% of CNS events are said to have ST changes
    • look for prolonged QTc which occurs in 71% of SAH, 50% of ICH, 28% of ischaemic stroke
  • dissecting aortic aneurysm
  • overdose of a heterocyclic antidepressant
  • cocaine-induced coronary spasm
  • hypothermia - check for an Osborn J wave
  • pulmonary embolism (PE) - generally causes “non-specific ST changes” +/- RBBB, axis deviation, anterior or global T inversion or P pulmonale.
  • hypercalcaemia - check for short QTc and in extreme cases, Osborn J waves
  • pectus excavatum
  • effects of athletic training
• rare conditions:
  • mediastinal tumor or hemopericardium compressing the right ventricular outflow tract (RVOT)
  • arrhythmogenic right ventricular dysplasia and/or cardiomyopathy
  • Duchenne muscular dystrophy
  • Friedreich ataxia
  • thiamine deficiency

• if concave with PR segment depression > 0.5mm, consider pericarditis
• if upwardly bowing ST segment in inf. leads with inverted T waves, consider inferior Wellen's syndrome (critical stenosis of RCA)
• if convex, consider inferolateral AMI
  • don't forget to look for features of associated RV infarct (eg. ST elevation in V1) or AV block