Final answer:
Sinus bradycardia is a slow heart rate arrhythmia that is usually not clinically significant unless accompanied by symptoms. It can result from various intrinsic or extrinsic factors, with treatment tailored to the underlying cause. A pacemaker may be needed in severe cases.
Step-by-step explanation:
Sinus bradycardia is a type of arrhythmia characterized by a heart rate (HR) that is slower than the normal range, which is 60-100 beats per minute (bpm) for adults. In sinus bradycardia, the HR drops below 60 bpm, with each heartbeat preceded by a normal P wave and followed by a normal QRS complex, indicating normal electrical activity through the heart's conduction system. This condition is considered significant only if accompanied by symptoms like weakness, dizziness, or fainting, suggesting inadequate oxygenated blood supply to body tissues.
Causes of bradycardia include inherent factors such as abnormalities in the sinoatrial (SA) or atrioventricular (AV) nodes, and external factors like metabolic or endocrine disorders, electrolyte imbalances, or drug effects. Treatment depends on identifying the underlying cause. Severe cases might require the implantation of a pacemaker to regulate the heart's rhythm. While bradycardia is common among trained athletes due to physiological adjustments, it typically becomes cause for concern if symptomatic or detected in individuals who are not well-conditioned.