Electrocardiography (ECG)
Sino-Atrial Node
Elliptical area at junction of SVC and Right atrium
Atrio-Ventricular Node
Triangular area of right atrial wall just above septal cusp of tricuspid valve
Lead positions
- Limb leads
- Right arm
- Left arm
- Left leg
- Chest leads
- V1: 4ICS Right sternum
- V2: 4ICS Left sternum
- V3: Midway between V2/4
- V4: Apex 5ICS MCL
- V5: 5ICS AAL
- V6: 5ICS MAL
- P-wave: passage of current across atrium
- PR interval: time from SA node to ventricle
- QRS: Ventricular depolarisation 0.12s
- QT: Time from ventricular depolarisation to full repolarsiation (rate dependent) hence QTc = corrected for heart rate (QT/rootRR interval) = Bazett's formula
- T-wave: ventricular myocardial repolarisation
- J-wave; J-point is at junction of Swave and ST segment (may be seen in hypothermia)
- U-wave: Prominent in hypokalaemia
Sinus Tachy: exercise, pain, pyrexia, shock, hyperthyroidism, anaemia, drugs
Sinus Brady: Atheletes, hypothyroidism, (Cushing reflex), drugs - B-blockers
Supra-ventricular tachycardias
- Atrial ectopics
- SVTs
- AF / Fibrillation
Bradyarrythmias
- First degree heart block
- Second degree heart block
- Mobitz type I: Wenkenbach
- Mobitz type II: 2:1 / 3:1 block
- Third degree (complete) heart block