What primarily contributes to premature atrial or junctional beats?

What primarily contributes to premature atrial or junctional beats?

• A. Increased oxygen levels.
• B. Stimulation from adrenergic substances.
• C. Low heart rates.
• D. Pacing from the SA node.

Answer: (B)

Premature atrial or junctional beats are primarily triggered by increased excitability of the atrial or junctional tissue, which can occur due to various factors, including the presence of adrenergic substances, such as adrenaline. This stimulation enhances the automaticity of the cells within these areas, causing them to fire prematurely and result in ectopic beats. In the context of a patient experiencing stress, anxiety, or other physiological changes that elevate adrenergic activity, these premature beats become more likely.

Other factors, such as inflammation, electrolyte imbalances, or ischemia, can also play a role, but adrenergic stimulation is a primary contributor. The other options listed do not directly lead to the onset of premature atrial or junctional beats; for instance, increased oxygen levels would not stimulate ectopic rhythms, low heart rates might actually decrease the likelihood of such beats due to reduced automaticity, and while pacing from the SA node is essential for normal rhythm, it does not contribute to premature beats when there is an ectopic focus.