Final answer:
Junctional bradycardia generally refers to a lower than normal heart rate due to issues with the heart's conduction system, specifically the AV node or junction, and not a rate less than 20. Treatment depends on identifying the cause, with a pacemaker as a potential corrective measure for severe cases.
Step-by-step explanation:
Junctional bradycardia is not specifically defined by a heart rate less than 20. Instead, bradycardia in general is a condition where the resting heart rate is below 60 beats per minute (bpm). Junctional bradycardia can be indicative of an underlying abnormality in heart conduction at the atrioventricular (AV) node or within the AV junction itself. Without the influence of the sinoatrial (SA) node, the heart's pace can slow significantly, leading to potential bradycardic conditions. In terms of inherent firing rates for parts of the heart, the AV node would be expected to generate impulses at 40-60 bpm, with the Purkinje fibers firing at 15-20 bpm if the higher pacemaking structures fail. Extremely low heart rates, such as under 50 bpm, can lead to inadequate blood flow and oxygen delivery to vital tissues, potentially causing symptoms like dizziness, fatigue, or even unconsciousness.
Treatment of bradycardia requires identifying the cause, which could range from inherent heart node abnormalities to external factors like metabolic disorders, electrolyte imbalances, or medication effects. In severe cases, a pacemaker may be necessary to maintain an adequate heart rate, ensuring sufficient cardiac output to meet the body's requirements.