Final answer:
Sinus bradycardia is a condition where the resting heart rate falls below 60 bpm. It can be caused by inherent factors or external factors, and treatment depends on the underlying cause.
Step-by-step explanation:
Sinus bradycardia is a condition characterized by a resting heart rate (HR) below 60 beats per minute (bpm). In a normal sinus rhythm, the SA node initiates impulses at a rate of 80-100 bpm. However, if the HR falls much below 50 bpm, the heart may not be able to provide sufficient oxygenated blood to vital tissues. Sinus bradycardia can be caused by inherent factors like abnormalities in the SA or AV node, or external factors like metabolic disorders, electrolyte imbalances, or over-prescription of beta blocker drugs. Treatment depends on identifying the underlying cause and may include a pacemaker or supplemental oxygen.