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patterns of ECGs

Obvious arrhythmias:

Bundle branch block or paced rhythm which may make interpretation of ischaemic changes difficult:



  • ECG criteria:
    • LAD of -45 to -90deg
    • small q wave 1-4mm in lead I
    • small r wave 1-4mm in lead III
    • normal QRS provided RBBB absent
  • aetiology:
    • IHD
    • chronic LVF
    • cardiomyopathy
    • Chaga's disease
    • children with endocardial cushion defect or tricuspid atresia


  • uncommon as is short, thick with dual blood supply thus avoid making Dx
  • ECG criteria (inaccurate though!):
    • small r wave (<5mm) lead I & small q wave in leads III, aVF
    • normal QRS duration
    • exclude RVH and cor pulmonale

Acute myocardial infarct or ischaemia

Specific drug effects:

digoxin effect:

  • reversed tick: ST depression & T inv. in V5-6
  • toxic effects:
    • any arrythmia esp. ventricular ectopy, nodal bradycardia
    • NOT rapid AF

tricyclic OD:

  • sinus tachycardia
  • wide QRS
  • prolonged QTc
  • VT/VF

heart block:

  • digoxin
  • beta blockers
  • calcium channel blockers
  • lithium (sinus arrest rather than AV block)

wide QRS with prolonged QTc (although maybe normal):

  • V-W class Ia drugs
  • V-W class III drugs
  • antipsychotic overdoses

wide QRS with normal QTc:

  • flecainide
  • moricizine
  • phenytoin (but not lignocaine which has no effect on either)
  • propranolol

Electrolyte disturbances:

    • ⇒ tall tented T waves, widening QRS, loss of P wave, etc and eventually sinusoidal appearance, VF or asystole
    • ⇒ ST depression, T wave flattening, prominent U wave creating a prolonged QTc effect, torsade de pointes VT
    • ie. similar ECG effects as has lithium toxicity, although lithium toxicity is also characterised by sinus node dysfunction causing bradycardia, sinus arrest with junctional escape rhythm or asystole, and unlike hypokalaemia, ventricular arrhthmias are rare.
    • ⇒ shortened QTc


  • see also pericarditis for the classic four stages of ECG changes
  • NB. tachycardia may be the only ECG finding if ST elevation has resolved & T waves remain normal

benign early repolarisation




dilated cardiomyopathy

hypertrophic cardiomyopathy

restrictive cardiomyopathy

dysrhythmogenic RV cardiomyopathy

Pulmonary embolus:

  • non-specific right atrial strain patterns but these are often not present
  • no significant abnormality in up to 25% of sub-massive PEs
  • sinus tachycardia common if acute
  • SI, QIII, TinvIII but not sens. and not spec.
  • strain pattern V1-3 - symmetrical T wave inversion
  • ST depression I or II
  • SI, SII and SIII pattern
  • Q waves in III & aVF
  • Qr in V1
  • ST elevation in V1, aVR & III
  • RAD
  • RBBB
  • AF or atrial flutter

pre-excitation syndromes:


  • shortened PR interval
  • delta wave
  • dominant R in V1
  • wide or narrow complex SVTs
ecg_patterns.txt · Last modified: 2012/12/14 15:35 (external edit)