Cardiac Conduction
Leads
- Anterior - V1 - V4
- Lateral - I / aVL / V5 / V6
- Inferior - II / III / aVF
What’s the Rhythm?
Normal Sinus Rhythm (NSR)
- Must meet these criteria:
- Regular
- Rate 60-100 bpm
- PR interval is normal & constant
- A P wave precedes each QRS complex
- QRS width <120msecs
What’s the Rhythm?
Inferior MI
- ST elevation eq/gr 1mm Lead II / III / aVF
- Progressive development of Q waves in leads II / III / aVF
- Reciprocal ST depression in aVL (+/- lead I)
What’s the Rhythm?
Inferior MI - Right Ventricular (RVMI)
- If elevation in II / III / aVF then check V4R - look for elevation >0.5mm
- If elevated in V4R and hypotensive give fluid bolus (250ml) to improve preload/improve cardiac output
- If RVMI confirmed then avoid repeat GTN
What’s the Rhythm?
Left Main (Widow Maker) Anterior MI
- ST depression eq/gr 1mm in 6 or more leads
- coupled with ST elevation in aVR and/or V1
- Suggestive of multi-vessel ischaemia or LMS insufficiency
ST Depression/ T Wave Inversion in aVL
- Can be reciprocal changes to an impending inferior MI
- Get serial ECG’s
What’s the Rhythm?
Sinus Bradycardia
- Regular
- Rate <60 bpm
- Popping P waves
- Each P followed by a QRS
- PR normal & constant
What’s the Rhythm?
Sinus Tachycardia
- Regular
- Rate >100 bpm <150 bpm
- Popping P waves
- Each P followed by QRS
- PR normal & constant
What’s the Rhythm?
Atrial Fibrillation
- Irregularly irregular
- No POPPING P waves
- Rate may be slow, normal or fast
- QRS usually normal
High Risk of Stroke, anticoagulation therapy is commonly used.
What’s the Rhythm?
Atrial Flutter
SA node signal blocked, so fired around atria:
- Usually regular
- No POPPING P waves
- FLutter (F) waves - saw tooth appearance
- Atrial rate around 300 bpm
- Relationship between atrial & ventricles is expressed as a ratio
- If the block is constant - rhythm regular
- Varying block - Rhythm irregular
What’s the Rhythm?
Atrial Ectopics
- Originates from a focus in the atria
- Usually P wave is abnormal in shape - NOT POPPING!
- Usually normal QRS
- Followed by compensatory pause
What’s the Rhythm?
Sinus Rhythm with Unifocal Ventricular Ectopics
- Rhythm regular
- PR interval normal
- QRS normal
- If associated with an MI - increases mortality
- Usually benign
What’s the Rhythm?
Sinus Rhythm with Multifocal Ventricular Ectopics
- Rhythm irregular
- PR interval normal
- QRS normal
- Excitable myocardium - increased risk of ventricular arrythmias
What’s the Rhythm?
Sinus Rhythm with R on T Ectopics
- Regular rhythm
- PR interval normal
- QRS normal
- May precipitate a fatal arrythmia (usually VF)
- If >10 per minute concern should be greater
What’s the Rhythm?
Ventricular Tachycardia (VT)
- Very broad complexes (>160ms).
- Absence of typical RBBB or LBBB morphology.
- Extreme axis deviation (“northwest axis”) — QRS is positive in aVR and negative in I + aVF.
- AV dissociation (P and QRS complexes at different rates).
- Capture beats — occur when the sinoatrial node transiently ‘captures’ the ventricles, in the midst of AV dissociation, to produce a QRS complex of normal duration.
- Fusion beats — occur when a sinus and ventricular beat coincide to produce a hybrid complex of intermediate morphology.
- Positive or negative concordance throughout the chest leads, i.e. leads V1-6 show entirely positive (R) or entirely negative (QS) complexes, with no RS complexes seen.
- Brugada’s sign – The distance from the onset of the QRS complex to the nadir of the S-wave is > 100ms.
- Josephson’s sign – Notching near the nadir of the S-wave.
- RSR’ complexes with a taller “left rabbit ear”. This is the most specific finding in favour of VT. This is in contrast to RBBB, where the right rabbit ear is taller.
What’s the Rhythm?
Narrow Complex Tachycardia
- Rate >100 (usually >150 bpm)
- Regular
- QRS normal - narrow (<120msecs)
- Absence of P waves
What’s the Rhythm?
Left Axis Deviation
- Leads I & aVL are +
- Leads II, III & aVF are -
What’s the Rhythm?
Right Axis Deviation
- Leads I & aVL are -
- Leads II, III & aVF are +
What’s the Rhythm?
Brugada
RBBB
+
V1/2 has cone shaped elevation extending into inverted T wave
What’s the Rhythm?
Wolf Parkinson White (WPW)
- Slurred upstroke of QRS (delta wave)
- Short PR interval
What’s the Rhythm?
Hypertrophic Cardiomyopathy
- Deep Q waves in lateral (V5/6,I,aVL) & inferior (II,III,aVF)
- Tall QRS
- Inverted T waves
High Risk ACS
T wave inversion
or
ST depression
(any 2 leads)
+
PT looks unwell AND has ACS pain
What’s the Rhythm?
Sudden Cardiac Death
- Long QT
- Male >440
- Female > 460
- Polarisation abnormality leads to VT
- (Worry when QTc exceeds >500msecs)
