Typical Atrial Flutter (AFL) is the most common type of atrial flutter and is a macro-reentrant right atrial tachycardia that uses the cavo-tricuspid isthmus as an essential part of a counter-clockwise circuit. The tendon of Todaro, the crista terminalis, the inferior vena cava, the tricuspid valve annulus, and the coronary sinus os provide anatomical landmarks of the circuit. Typical AFL can be described as having a “sawtooth” appearance from an aVF ECG vector used with the Carnation monitor. AFL can manifest with either a regular or irregular ventricular response depending upon AV node conduction. AFL, when regular in its ventricular response, will manifest fractions of its atrial cycle length. Atrial rates typically range between 220-320 bpm. AFL can have fixed atrial-to-ventricular conduction ratios of 1:1, 2:1, 3:1, 4:1 or, as often occurs, variable AV conduction superficially mimicking AF, albeit with much less randomness than true AF. The key takeaway here is that typical atrial flutter waves will be the same and its ventricular response can be an exact fraction of its atrial cycle or vary.
55-year-old male with a history of Atrial Fibrillation, complaining of dizziness, lightheadedness, and palpitations. This patient had a 12-day, 8-hour study with 100% typical AFL throughout the recording. Episodic ratios of AFL occurred at 1:1, 2:1, 3:1, 4:1 and also included variable AV conduction.
Example Strips
These R-R plots suggest variable AV conduction ratios of AFL. However, there are brief periods of fixed ratio conduction, as shown in the following near-field ECG examples. The first is 2:1 AFL AV conduction at ventricular rates in the 130-140 bpm range. Note that 2:1 AFL manifests on the R-R ‘tract’ where highlighted by the blue rectangle. The second example is 3:1 AFL (red rectangle ‘tract’) at heart rates in the 90-100 bpm range and seems to be the dominant rhythm in this R-R plot. The third example is 4:1 AFL (yellow rectangle ‘tract’) at heart rates of ~70 bpm.
The First Example:
The near-field ECG below represents AFL with 2:1 AV conduction. See blue rectangle ‘tract’ in R-R plot. Note that other findings in R-R plot will be clarified below.
The Second Example:
The near-field ECG below represents AFL with 3:1 AV conduction. See red rectangle ‘tract’ in R-R plot.
The Third Example:
The near-field ECG below represents AFL with 4:1 AV conduction. See yellow rectangle ‘tract’ in R-R plot. As shown here and elsewhere in the various R-R plots shown in this study, AFL AV conduction is highly variable over time periods that extend for more than a few seconds.
The Fourth Example:
This R-R plot shows an abrupt heart rate and AV conduction change. Note three instances of this rapid change in heart rate. On the near-field (8-second ECG) view, the patient is in 1:1 AFL. In the intermediate ECG (56-second ECG), the patient has stuttered from 2:1 to 1:1 AFL before stabilizing in 1:1 AFL at rates of 262 bpm (orange arrow). Time of day suggests possible early morning exercise. The combination of exercise and 1:1 AFL potentially places the patient at risk of cardiac arrest.
The Fifth Example:
On this R-R plot, as with the previous examples, variable AV conduction is present. The dominant AV conduction ratio is 3:1 at ~90 bpm (red rectangle). However, the 8-second strip clearly shows AFL with variable conduction and classic “sawtooth” P-waves. The ability of the CAM to clearly identify a lack of change in atrial morphology and atrial rate allows us to confidently diagnose this as AFL with variable conduction instead of AF even though the ventricular response on the ECG tracing is quite irregular. R-wave centric technologies will typically and inappropriately diagnose this as AF.
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