Expansion
Purkinje fastest, atrioventricular node slowest
Expansion
Park At Ventricular Avenue, fastest to slowest:
- P - Purkinje fibres, about 4 metres per second
- A - Atrial muscle, about 1 metre per second
- V - Ventricular muscle, about 0.4 metres per second
- A - Atrioventricular node, about 0.05 metres per second
The extremes are the functionally important ones.
The Purkinje system is fast so that the ventricles depolarise almost simultaneously, producing a coordinated squeeze from apex to base.
The atrioventricular node is deliberately slow, giving the delay seen as the PR interval. This allows atrial contraction to complete ventricular filling before systole, and it protects the ventricles by limiting the rate that can be conducted in atrial fibrillation or flutter.