Characteristics of Typical Atrial Flutter

Author: Alec Feuerbach

Peer Editor: Nicole Anthony

Faculty Editor: Mark Silverberg

This week we have two ECGs to examine. The first is the ECG of a 50-year-old woman who presented to the ED after experiencing uncomfortable palpitations and lightheadedness.

ECG 1:

This ECG shows a rapid ventricular rate of about 135/min with narrow QRS, regular rhythm, and normal axis. T waves are difficult to discern from P waves given the rapidity of the heart rate.

The second is from a 55-year-old man who was sent in by his cardiologist for an abnormal ECG after endorsing symptoms of nocturnal dyspnea.

ECG 2:

This ECG similarly shows a rapid rate with a narrow QRS; however, this ECG has an irregular rhythm.

The most striking feature of both ECGs is the morphology of the P waves, seen especially well in lead II of the second ECG. These P-waves demonstrate the classic “saw-tooth” morphology of Atrial Flutter.

Atrial Flutter results from a reentry circuit within the right atrium which typically produces an atrial of around 300/minute. Since not all of these atrial beats are conducted by the AV node, the ventricular rate can be variable.

In typical atrial flutter the reentry circuit occurs in the right atrium and involves the IVC and tricuspid isthmus.[1] Ninety percent of cases of Atrial Flutter have a counter-clockwise reentry which can be seen on the ECG with negative flutter waves in the inferior leads (II, III, aVF) and positive flutter waves in V1.[1] Both of the above ECGs demonstrate typical atrial flutter with a counter-clockwise reentry; to visualize this, imagine the baseline as a straight line connecting the ends of the S waves.

Some cases of atrial flutter can have clockwise reentry through the same “typical” pathway. Not surprisingly, these will have the opposite pattern: positive flutter waves in the inferior leads and a negative flutter wave in V1.

There are also atrial flutter pathways that do not follow this ECG pattern and involve some other reentry pathway. Though this is unlikely to change management in the ED, it is worth being aware of these variations of flutter as typical atrial flutter involving the cavo-tricuspid isthmus is much more likely to be ablated successfully because the pathway is known and can be targeted. An atypical pathway is difficult to find and, therefore, harder to ablate.[2]

As found in the two ECGs above, atrial flutter can result in varied rates of ventricular conduction, even in a single ECG. The first ECG shows 2:1 conduction — which is common — resulting in a rate of 135/min. For 2:1 conduction, the ventricular response rate is generally between 120 and 150/min, half the atrial rate which, as mentioned earlier, is typically around 300/minute. The second ECG shows variable degrees of AV conduction with some rhythms reflecting 2:1 conduction and others with 3:1 conduction.

In the ED, management of patients with atrial flutter depends, first, on the stability of the patient.[3] As with other tachydysrhythmias, unstable patients — think hypotension, altered mental status (cerebral hypoperfusion), and respiratory failure (elevated LV pressure and pulmonary congestion) — with atrial flutter should be electrically cardioverted.

If patients are stable, rate control can be attempted; however, before trying to slow the patient’s heart rate it is important to assess the patient and try to identify any underlying cause for the tachycardia. A 2014 study found that attempting rate or rhythm control in patients with “complex” atrial fibrillation or flutter (complex meaning in the setting of another illness such as sepsis or heart failure) resulted in a “nearly 6-fold increase in adverse events and a nearly 12-fold increase in major adverse events”.[4] This does not necessarily mean that all patients with atrial flutter and other conditions in the ED do not need their rate controlled as a rate too fast to allow for proper filling time can contribute to hypoperfusion. Still, the managing physician should generally prioritize the appropriate identification and management of other underlying conditions rather than immediately jumping to control the rate.

Once other causes of tachycardia have been ruled out or treated, rate control can be achieved with beta-blockers or calcium-channel blockers. The data does not favor one agent over the other,[5-8] so providers should consider the patient’s baseline ejection fraction, each drug’s pharmacokinetics, and underlying illness in choosing an agent. Another option, for patients with recent-onset of atrial flutter is to perform cardioversion. For a deeper dive into the intricacies of this management, check out this previous post on our County EM blog.

In both of the patients mentioned above, rate control was performed and they were admitted for possible radiofrequency ablation. Though both rhythm and rate control can be utilized, the long-term management goal for many patients with atrial flutter is the maintenance of sinus rhythm.[9] This decreases symptoms, theoretically can decrease the risk for stroke and cardiac remodeling, and can avoid the long-term use of high doses of rate-control medications.[10] Though rhythm control medications can be tried, for patients with typical flutter like the two presented here, radiofrequency ablation is a safe and effective method of obtaining long-term rhythm control. Indeed, a meta-analysis showed that the ablation was successful in maintaining sinus rhythm in over 90% of cases of typical atrial flutter for six to 48 months.[11] Another study lends additional support for early ablation given its role in reducing overall healthcare utilization.[12]

After transesophageal echocardiography showed no thrombi, both of the patients had successful ablation and were discharged home in normal sinus rhythm.

References

[1] Buttner R and Burns E. Atrial Flutter. Life in the Fastlane. https://litfl.com/atrial-flutter-ecg-library/. Published Feb 11, 2022

[2] Winkle RA, Moskovitz R, Mead RH, et al. Ablation of atypical atrial flutters using ultra high density-activation sequence mapping. J Interv Card Electrophysiol. 2017;48(2):177-184. doi:10.1007/s10840-016-0207-5

[3] Atzema CL, Barrett TW. Managing atrial fibrillation. Ann Emerg Med. 2015 May;65(5):532-9. doi: 10.1016/j.annemergmed.2014.12.010. Epub 2015 Feb 18. PMID: 25701296; PMCID: PMC4519094.

[4] Scheuermeyer FX, Pourvali R, Rowe BH, et al. Emergency Department Patients With Atrial Fibrillation or Flutter and an Acute Underlying Medical Illness May Not Benefit From Attempts to Control Rate or Rhythm. Ann Emerg Med. 2015;65(5):511-522.e2. doi:10.1016/j.annemergmed.2014.09.012

[5] Zaman N, Naccarelli G, Foy A. A Comparison of Rate Control Agents for the Treatment of Atrial Fibrillation: Follow-Up Investigation of the AFFIRM Study. J Cardiovasc Pharmacol Ther. 2021;26(4):328-334. doi:10.1177/1074248420987451

[6] Hayes B. Atrial Fibrillation Rate Control in the ED: Calcium Channel Blockers or Beta Blockers? ALiEM. https://www.aliem.com/atrial-fibrillation-rate-control-calcium-channel-blockers-or-beta-blockers/ Epub June 4, 2014

[7] Nicholson J, Czosnowski Q, Flack T, Pang PS, Billups K. Hemodynamic comparison of intravenous push diltiazem versus metoprolol for atrial fibrillation rate control. Am J Emerg Med. 2020;38(9):1879-1883. doi:10.1016/j.ajem.2020.06.034

[8] Reed B. Beta Blockers vs Calcium Channel Blockers for Atrial Fibrillation Rate Control: Thinking Beyond the ED. ALiEM. https://www.aliem.com/beta-blockers-vs-calcium-channel-blockers-atrial-fibrillation-rate-control-thinking-beyond-ed/. ePub Sep 8, 2014

[9] Prutkin J. Atrial flutter: Maintenance of sinus rhythm. UpToDate. https://www.uptodate.com/contents/atrial-flutter-maintenance-of-sinus-rhythm. ePub Nov 18, 2021

[10] Camm AJ, Naccarelli GV, Mittal S, et al. The Increasing Role of Rhythm Control in Patients With Atrial Fibrillation: JACC State-of-the-Art Review. J Am Coll Cardiol. 2022;79(19):1932-1948. doi:10.1016/j.jacc.2022.03.337

[11] Spector P, Reynolds MR, Calkins H, et al. Meta-analysis of ablation of atrial flutter and supraventricular tachycardia. Am J Cardiol. 2009;104(5):671-677. doi:10.1016/j.amjcard.2009.04.040

[12] Dewland TA, Glidden DV, Marcus GM. Healthcare utilization and clinical outcomes after catheter ablation of atrial flutter. PLoS One. 2014;9(7):e100509. Published 2014 Jul 1. doi:10.1371/journal.pone.0100509

Bio
Latest Posts

feuerbacham

Latest posts by feuerbacham (see all)

Characteristics of Typical Atrial Flutter - October 6, 2022
Interpreting a Paced Electrocardiographic Rhythm - August 18, 2022
Understanding Right Bundle Branch Block Morphology - July 26, 2022