Which of the following is a reversible cause of sinus bradycardia?

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Multiple Choice

Which of the following is a reversible cause of sinus bradycardia?

The main idea is that reversible factors, especially medications, can slow the SA node by dampening sympathetic stimulation. Beta-blockers reduce the heart’s automaticity by blocking beta-adrenergic receptors in the SA node, which lowers the slope of phase 4 depolarization and slows firing. This effect is reversible when the drug is stopped or the dose is adjusted, so the heart rate returns toward normal. Fever, caffeine, and epinephrine, in contrast, tend to raise heart rate or increase sympathetic activity rather than cause a reversible bradycardia, so they don’t fit as causes.

The main idea is that reversible factors, especially medications, can slow the SA node by dampening sympathetic stimulation. Beta-blockers reduce the heart’s automaticity by blocking beta-adrenergic receptors in the SA node, which lowers the slope of phase 4 depolarization and slows firing. This effect is reversible when the drug is stopped or the dose is adjusted, so the heart rate returns toward normal. Fever, caffeine, and epinephrine, in contrast, tend to raise heart rate or increase sympathetic activity rather than cause a reversible bradycardia, so they don’t fit as causes.

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