Interesting tracing by Dawn — which shows an irregularly irregular rhythm that is not AFib (Atrial Fibrillation). Looking closer — the QRS complex in this tracing is clearly narrow. There IS atrial activity. This is best seen in the inferior leads and in lead V1 — though it is also seen in other leads. The question arises as to whether the atrial activity we see is “organized enough” to constitute AFlutter (Atrial Flutter)?

• In this case — I believe atrial activity IS regular enough (there is no more than very minimal P-P variation, seen for some cycles in V1) — at a typical enough rate close to 300/minute (~280/minute in this tracing) — that I’d diagnose this exactly as Dawn did = AFlutter with a Variable Ventricular Response.
• Distinction between AFib vs AFlutter is not always clear-cut when the ventricular response is not regular. At times, AFib may “organize” (at least partially, usually within the right atrium) — such that waveforms resembling flutter are seen in lead V1, but not in other leads. Although superficially regular and sawtooth in pattern — such waveforms on closer inspection are not regular. Such rhythms are sometimes designated as, “AFib-Flutter” as a descriptive term to indicate that while the rhythm looks a lot like AFlutter on ECG — it “behaves” clinically as Fib.
• Clinically, distinction between AFib vs AFlutter is important for several reasons. While both AFib and AFlutter are increasingly susceptible to ablation as an effective treatment modality — AFlutter clearly responds better than AFib to ablation. Similar medications are used for both rhythms for initial treatment — but it may be more difficult to control the ventricular response to AFlutter than to AFib. Longterm anticoagulation is advised for both rhythms — but the risk of thromboemblism appears to be much greater for chronic AFib, given the much more disorganized nature of that rhythm.
• The most common ventricular response to untreated AFlutter is 2:1 AV conduction. At the typical AFlutter rate of ~300/minute — this results in a regular ventricular response that is often quite close to 150/minute. 4:1 AV conduction is the next-most-common ventricular response to AFlutter. 
• Variable conduction ratios (usually alternating at fixed intervals, such as 2:1; 3:2, etc.) are not uncommon with AFlutter. This is thought to be due to Wenckebach conduction of flutter impulses out of two or more levels within the AV node.
• Odd conduction ratios (1:1; 3:1, etc.) are rare with AFlutter (especially if the patient is not on medication and does not have WPW). 
• On occasion — AFlutter may conduct with a truly variable ventricular response. Whether this is the result of multiple variable Wenckebach conduction ratios out of different AV nodal levels, or simply random conduction (from concealed conduction) of flutter impulses through the AV node is uncertain. 

In Summary — I favor designation of the rhythm seen here as, AFlutter with a controlled but Variable Ventricular Response.