Final answer:
The most common extrinsic cause of sinus bradycardia is the over-prescription of beta blocker drugs. Other causes include metabolic and endocrine disorders, electrolyte imbalances, and neurological factors. Addressing the underlying cause is crucial for treatment, which may involve medication adjustments or a pacemaker if severe.
Step-by-step explanation:
Common Extrinsic Cause of Sinus Bradycardia
Bradycardia is a condition where the heart rate (HR) goes below the normal resting rate of 60-100 beats per minute (bpm). The most common extrinsic cause of sinus bradycardia includes over-prescription of beta blocker drugs that reduce heart rate. Besides medication, other external factors can lead to bradycardia such as metabolic disorders, pathologies involving the thyroid, electrolyte imbalances, disorders of the autonomic nervous system, and prolonged bed rest. These factors can decrease the excitability of the SA node or interrupt the normal autonomic regulation of the heart rate. To treat bradycardia adequately, it is imperative to identify the underlying cause which may require interventions like changes in medication, addressing electrolyte imbalances, or even the use of a pacemaker in severe cases.