Skip Navigation

School of Health Sciences > Practice Learning > Practice Learning Resources

Cardiology Teaching Package

A Beginners Guide to Normal Heart Function, Sinus Rhythm & Common Cardiac Arrhythmias

Sinus Bradycardia

The job of the heart is to pump blood around the body carrying oxygen and nutrients to organs, muscles and tissues, and transporting waste such as carbon dioxide to the lungs for expiration. The cardiovascular system is under the control of the nervous system which increases and decreases the workload of the heart depending on the body's requirements.

So, if a person is involved in exercise, their muscles and organs require more blood and oxygen to function, so the heart and lungs go faster. If a person is resting or sleeping then the body's requirements drop considerably and the heart and lungs slow down.

Anything below 60 bpm is known as Bradycardia. Sinus Bradycardia is not a changed rhythm, it is simply normal sinus rhythm slowed down.

Image: Sinus Bradycardia

Diagram of a Sinus Bradycardia rhythm
  • R-R intervals constant and regular
  • All waveforms are present, and there is 1 P-wave to each QRS complex
  • The rate is <60bpm but not usually <40bpm
  • Patients usually asymptomatic and no treatment is required
  • Often caused by beta-blockers / calcium channel blockers
  • May also be seen in athletes and occur during sleep.
  • Return to top of document
  • Previous page
  • Next page