What is the most common cause of sinus tachycardia?

• A. Sleep apnea
• B. Physiological stress, such as exercise or anxiety
• C. Atrial fibrillation
• D. Hypotension

Answer: (B)

Sinus tachycardia is characterized by an increased heart rate that originates from the sinus node, and the most common cause is physiological stress, such as exercise or anxiety. During physical exertion or episodes of heightened emotional states, the body's demand for oxygen increases, leading the autonomic nervous system to stimulate the heart to beat faster in order to supply the necessary blood flow and meet metabolic demands.

This response is a normal physiological adaptation. For example, during exercise, the body requires more oxygen, so the heart rate increases to ensure that tissues receive adequate blood supply. Similarly, anxiety can trigger the fight or flight response, which also results in an elevated heart rate. Both conditions are typically transient and resolve once the stressor is removed, making this cause of sinus tachycardia quite common in many individuals.

The other options represent scenarios that could lead to abnormal conditions or less common causes of tachycardia but are not as prevalent as physiological stress. Sleep apnea may lead to cardiovascular changes but is not a direct and immediate cause of sinus tachycardia like exercise or anxiety. Atrial fibrillation is a type of arrhythmia and is fundamentally different in mechanism from sinus tachycardia. Hypotension, while it can result in