• Rapid, erratic electrical discharge comes from multiple atrial ectopic foci.
• No organized atrial depolarization is detectable.

Rate: Atrial: equal to or greater than 350 bpm; ventricular: variable

Rhythm: Irregular

P Waves: No true P waves; chaotic atrial activity

PR Interval: None

QRS: Normal (0.06–0.10 sec)

Clinical Tip: A-fib is usually a chronic arrhythmia associated with underlying heart disease.

Clinical Tip: Signs and symptoms depend on ventricular response rate.