Which statement best describes not sinus rhythm?

• A. Not sinus rhythm
• B. Normal sinus rhythm
• C. Regular rhythm with consistent P waves
• D. Sinus rhythm with early P waves

Answer: (A)

Sinus rhythm means the heart’s rhythm starts in the SA node, with P waves before every QRS and a regular, predictable pattern. Saying “not sinus rhythm” captures the idea that the rhythm is not originating from the SA node, which is exactly what the question is asking to identify. Among the options, the other statements describe sinus rhythm or its variations: normal sinus rhythm describes a healthy SA node pattern, a regular rhythm with consistent P waves also fits sinus rhythm, and sinus rhythm with early P waves points to premature atrial activity but still originates from the atria in relation to the SA node. When a rhythm truly isn’t sinus, you’d expect missing or abnormal P waves, irregular timing, or a rhythm that doesn’t stem from the SA node.