An irregular and often rapid heart rhythm that begins in the atria is known as?

• A. A-fib
• B. A-flutter
• C. Sinus tachycardia
• D. Ventricular fibrillation

Answer: (A)

This item tests recognizing atrial-origin tachyarrhythmias by rhythm pattern. Atrial fibrillation is characterized by an irregularly irregular rhythm that starts in the atria, caused by chaotic electrical activity with many foci. Because the atrial activity is so disorganized, the ventricular response is unpredictable, often rapid. On ECG there are no stable P waves, just chaotic baseline activity or small fibrillatory waves, and the intervals between beats vary widely.

This differs from atrial flutter, which shows a more organized atrial rhythm with sawtooth flutter waves and a regular or regularly irregular pattern. Sinus tachycardia is fast but regular and originates from the sinoatrial node, so P waves are normal and the rhythm is steady. Ventricular fibrillation is chaotic activity arising in the ventricles and is life-threatening; it does not originate in the atria and requires immediate intervention.