• The AV node conducts impulses to the ventricles at a ratio of 2:1, 3:1, 4:1, or greater (rarely 1:1).
• The degree of AV block may be consistent or variable.

Rate: Atrial: 250–350 bpm; ventricular: variable

Rhythm: Atrial: regular; ventricular: variable

P Waves: Flutter waves have a saw-toothed appearance; some may not be visible, being buried in the QRS

PR Interval: None, not measurable

QRS: Usually normal (0.06–0.10 sec), but may appear widened if flutter waves are buried in QRS

Clinical Tip: The presence of atrial flutter may be the first indication of cardiac disease.

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