Atrial flutter involves two atrial rate patterns. Which statement accurately describes the typical rate ranges for Type I and Type II flutter?

• A. Type I (typical) 250-350 bpm; Type II 350-450 bpm
• B. Type I 350-450 bpm; Type II 250-350 bpm
• C. Both types irregular
• D. Type I not sawtooth waves

Answer: (A)

Atrial flutter has two common atrial rate patterns reflecting different reentrant circuits. The typical (Type I) flutter runs at about 250–350 beats per minute, while the atypical or Type II flutter is faster, usually 350–450 beats per minute. This difference comes from the underlying circuit length and cycle time: a shorter atrial cycle in Type II yields a higher atrial rate. On the ECG, this rapid, organized atrial activity often appears as sawtooth flutter waves. The ventricular rate varies with AV nodal conduction but doesn’t change the characteristic atrial rate ranges. Options suggesting 350–450 for the slower pattern, or claiming both types are irregular, or denying sawtooth waves, don’t align with how the atrial rate patterns in flutter typically present.