Flutter or not!
Flutter or not!
By CMS Director of Medicine Dr Harry Mond
OAM MBBS MD FRACP FCSANZ FACC FHRS DDU
Recently we had a request from a cardiologist to review and “correct” two ECGs, which were reported as supraventricular tachycardia and he stated were actually atrial flutter. Before I saw the ECGs, I knew exactly what the issue was. I also took the opportunity of sending the tracings to three electrophysiologists for their opinion.
Typical (counter clockwise) atrial flutter is a single wave circus movement or a macroreentrant mechanism in the right atrium. There is an atrial rate >240bpm with a negative saw tooth pattern in the inferior leads and P waves often almost isoelectric in leads I and aVF.
Atypical atrial flutters are less common and can arise from other areas of the left or right atria or pulmonary veins. They have different “atypical” patterns. Apart from rate, the other criterion is that there is no return of the P waves to the baseline between deflections. With the advent of intracardiac electrograms, EP studies with computerized electro-anatomical mapping and antiarrhythmic drugs, neither of these criteria are rigid and the rules change. Of interest look at the P waves in V1, where the baseline is clearly seen.
With antiarrhythmic therapy such as flecainide without digoxin, the flutter rate can be reduced below 240 bpm and now conduct 1:1.
Despite the absence of P waves, everyone would call this atrial flutter, despite the rate being <240bpm. Atrial flutter frequently deteriorates into atrial fibrillation and it can be difficult to determine when one finishes and the other starts, although irregularity of the rhythm is a clue.
On occasion, we see an atrial rhythm of 300bpm without conduction to the ventricle, because of a block at the ectopic-myocardial junction. Because this is does not appear re-entrant, it is regarded as a focal atrial tachycardia. The episodes are usually short lived and the termination is due to Wenckebach block.
If this isn’t flutter, then it should not occur in patients with flutter!!
Here we have both focal and re-entrant in the same patient or do we?
This is another one we had this week; focal or flutter?
Now, what about the two cases, we were asked to call atrial flutter!
I haven’t a clue!
So how do we report these ECGs with atrial rates of 300bpm?
Clear saw tooth pattern is typical and easy.
Not saw tooth and a baseline between P waves, then this is atypical flutter and should be called this, although a “focal” atrial tachycardia is acceptable.
Lousy P waves or irregular ventricular response, think outside the box. Consider atrial fibrillation.
Actually, in practice, it really doesn’t matter what you call these atypical atrial tachyarrhythmias in elderly people (elderly is defined as older than me!!). If they get an EP study, then we will get the answer. If not, then most will soon go into atrial fibrillation and should be treated as such.
I think our reporters were correct in not calling those ECGs atrial flutter, but it is not easy.
Jitu Vohra provided two excellent references which I have enclosed.
I hope I have stirred up enough emotion to warrant a reply and criticism.
Dr Harry Mond.