Which cardiac arrhythmia is commonly linked to respiratory variations in heart rate?

Sinus arrhythmia is characterized by variations in heart rate that occur with respiration. This physiological phenomenon is most commonly seen in younger individuals and is generally considered a normal variant, particularly during deep breathing. As a person inhales, the heart rate increases, and as they exhale, the heart rate decreases, reflecting the influence of autonomic nervous system regulation on the heart. The vagus nerve plays a significant role here, as increased vagal tone during exhalation slows the heart rate, while decreased vagal tone or increased sympathetic activity during inhalation speeds it up.

In contrast, atrial fibrillation is characterized by an irregular and often rapid heart rate, with no relationship to the respiratory cycle. Sinus tachycardia occurs due to increased heart rate generally caused by factors such as stress, fever, or exercise, but it lacks the respiratory-induced variations seen in sinus arrhythmia. Ventricular tachycardia is a more serious arrhythmia that arises from the ventricles and often results in a consistent and rapid heart rate that does not vary with respiration. Thus, sinus arrhythmia is the only choice that directly correlates with respiratory variations in heart rate.