Sinus Bradycardia

If the body’s requirement for blood is reduced (such as at times of rest or sleep), the autonomic nervous system slows the rate at which the sinus node initiates heartbeats.

As the sinus node is still pacing beats of normal conduction the rhythm is termed sinus bradycardia. The upper threshold of the rate varies but is normally considered as 50 bpm.

Conduction: Sinus Bradycardia

The following ECG trace shows a slow, regular heart rate at 41 bpm. Each QRS complex (shaded) is preceded by a P wave (arrowed) of regular shape and offset.

Electrocardiogram: Sinus Bradycardia
Electrocardiogram: Sinus Bradycardia