A flutter vs Atrial Tach w/ block

[VFlutter]

Lately I have noticed that many providers (Medics, RNs and even some MDs) just label any rhythm with multiple P waves Atrial Flutter. The way I was taught was to distinguish between Atrial Flutter and Atrial Tachycardia with Av block. Does anyone else do this? Or is it just irrelevant to most providers except for cardiologist. Or maybe most people are not taught to distinguish the two just to make things easier. Anyway here is a break down of how I distinguish the two:

Atrial tach w/ block : regular or irregular rhythm containing multiple distinct P waves per QRS. If there is variable block some QRS may only have a single P wave at times but usually a wandering PR interval. The atrial rate is 150-250

Atrial flutter: Usually regular rhythm contain multiple p waves per QRS however not distinct p waves, usually "sawtooth" or F waves. Atrial rate 250-400


Maybe I am off on my interpretation of this but that Is how I understand it. I am assuming in the pre-hospital world it would not make much of a difference and would be treated the same. So any input?

 

[Christopher]

I don't think your definitions are incorrect, however, I would add that sometimes atrial flutter has morphologies which stretch the imagination of "saw-tooth". The functional distinction is that AT is an automatic tachycardia while AF is a macro-reentry tachycardia. Either way, Atrial tachycardias and atrial flutter are likely going to require similar pre-hospital treatment.

Garcia-Cosio F, Fuentes AP, Angulo AN. Clinical approach to atrial tachycardia and atrial flutter from an understanding of the mechanisms: Electrophysiology based on Anatomy. Rev Esp Cardiol. 2012: Article in Press.

The classic categorization of atrial tachycardia and atrial flutter based on rate and morphological criteria has become almost irrelevant at a time when clinical electrophysiology may lead to curative intervention based on a definition of the mechanism, making it necessary to bring laboratory experience closer to clinical practice.

As you noted, AT and AF are usually easily distinguished due to rate and morphology, but this is only when they "live within their means" and are functioning at average rates (i.e. a regular atrial tachycardia at 150 w/ a 2:1 block versus atrial flutter at 300 w/ a 2:1 block).

When the ECG shows tachycardia in a patient without heart disease, with paroxysmal presentation and well-defined P waves at rates between 180 bpm and 220 bpm, and it can be observed that atrioventricular (AV) conduction is not constant (Wenckebach periodicity or 2:1 block) during tachycardia, the most likely diagnosis is FAT (Ed: Focal Atrial Tachycardia). If the rate accelerates at the beginning of the tachycardia and decelerates before spontaneous termination (the ‘‘warm-up and cool-down’’ phenomenon), a focal mechanism due to abnormal automaticity is almost certain. If the patient does not show spontaneous AV block, this can be induced by vagal maneuvers or intravenous injection of adenosine triphosphate (ATP) or adenosine. The interruption of the tachycardia using these maneuvers increases the likelihood that the mechanism is a reentry involving the AV node (intranodal or by accessory pathway).

The paper continues:

When the ECG records a tachycardia >240 bpm with a pattern typical of counterclockwise or clockwise AF (already mentioned) and fixed or variable AV block in a patient with or without organic heart disease and with no prior cardiac surgery, then the diagnosis of CTI-dependent typical AF is almost certain. If the waveform morphology is not well defined, the degree of AV block can be increased by carotid massage or an injection of ATP or adenosine, while making recordings of the limb leads and lead V1. In patients with prior surgical atriotomy the typical ECG pattern of AF is no longer specific.

Given an ECG pattern of atypical AF, the possibilities are many, including FAT or MLAT (Ed: Macro-reentry Left Atrial Tachycardia; a loop between the atria), especially when there has been prior cardiac surgery or ablation of the atrial myocardium for the treatment of atrial fibrillation. In patients with complex atrial lesions, not even the pattern of typical AF can predict the mechanism of tachycardia; FAT and MAT mechanisms may also be present.

I think with the the vast degree of overlap in both possible rates and morphologies--either due to internal or external forces--the distinction may not always be reliably made from the surface ECG alone!

Where you worry is when you reach for an antiarrhythmic. The 2:1 block most commonly seen in atrial flutter is a rate-related block. Class I antiarrhythmics (e.g. procainamide) could cause the reentry loop caused by atrial flutter to slow to rates which the AV node can conduct! Ouch.

Rate control with beta-blockers or Ca-channel blockers may be helpful, however, electrical cardioversion is the safest choice.

 

[VFlutter]

Thank you, Great Info! I agree there is a lot of overlap and sometimes it is not always clear cut however there are some circumstances where I think AT is pretty obvious (ie. Atrial rate of ~100). It seems to be common in patients with valvular diseases or post op patients

It just seems that anytime I mention AT to anyone other than a cardiologist I got a lot of blank stares and questions. Most have never heard the term before.

 

[mycrofft]

Here's a nice web page

http://cardiology.ucsf.edu/patients/ecg.html

 

[jwk]

Thank you, Great Info! I agree there is a lot of overlap and sometimes it is not always clear cut however there are some circumstances where I think AT is pretty obvious (ie. Atrial rate of ~100). It seems to be common in patients with valvular diseases or post op patients

It just seems that anytime I mention AT to anyone other than a cardiologist I got a lot of blank stares and questions. Most have never heard the term before.

Probably because most people will refer to it as a sinus tachycardia, not an atrial tachycardia.

 

[VFlutter]

Here is an example of what I would call Atrial Tachycardia with variable AV block

 

[Christopher]

Here is an example of what I would call Atrial Tachycardia with variable AV block

Leads II and MCL1? A 12-lead would help with AT vs AFL, but I'm with you that it "looks" more like AT even if the rate is in the sweet spot for flutter.

As for the block, it looks like Wenckebach behavior (the R-Rs decrease in each group).

 

[VFlutter]

Yes, II and MCL. The strip is off of a telemetry monitor, I will try to get a copy of their 12 lead.

 

[ZootownMedic]

I am not really sure where that rhythm is even close to being called AFL.....

Its Irregularly irregular, no F waves, ventricular rate isn't at 150 bpm, discernible P-waves with slightly increasing PRI (Wenckebach? Could be 2:1 untypable....?).....all I am saying is if I saw that strip I wouldn't think AFL at all.

 

[VFlutter]

I am not really sure where that rhythm is even close to being called AFL.....

Its Irregularly irregular, no F waves, ventricular rate isn't at 150 bpm, discernible P-waves with slightly increasing PRI (Wenckebach? Could be 2:1 untypable....?).....all I am saying is if I saw that strip I wouldn't think AFL at all.

Atrial flutter should be included in the differential diagnosis based on the presence of multiple p waves per QRS complex and an Atrial rate ~200. Also AFL is usually regular but can be irregular due to a variable heart block and irregular conduction to the ventricles. So an irregular R-R alone does not exclude AFL. However irregular nature of the p waves is highly suspect.