Approach Considerations
A 12-lead to 15-lead electrocardiogram (ECG) is the mainstay of atrial flutter diagnosis. Atrial flutter is a reentrant arrhythmia circuit confined to the atrial chambers. Such a circuit may be macroscopic and, therefore, amenable to mapping by techniques using standard electrophysiologic catheters or it may be microscopic and amenable to mapping only in the research laboratory using fine electrode arrays.
Depending on the drug used, patients receiving antiarrhythmic therapy may benefit from the monitoring of specific drug blood levels and electrolyte and creatinine levels or ECG monitoring of the QTc (eg, class III agents).
Electrophysiologic studies may be useful for mapping arrhythmia circuits. Consider transesophageal echocardiography in patients with associated structural or functional heart disease to ascertain the presence of intracardiac thrombi, myocardial dysfunction, or hemodynamically important residual structural defects that could predispose them to atrial flutter.
Coagulation studies
Optimize anticoagulation through monitoring of coagulation profiles in patients receiving heparin or warfarin. In patients with documented intracardiac thrombi, monitor for the presence of associated thrombophilia, as indicated.
Electrocardiography
A rapid atrial tachycardia with uniform P waves with flutter morphology and variable atrioventricular (AV) block indicates that atrial flutter or atrial ectopic tachycardia is present. See the image below.
Rhythm strip depicting lead II of a patient with atrial flutter with an atrial rate of 300 beats per minute (bpm). Atrioventricular conduction rate is variable at 2:1 and 3:1. Therefore, the ventricular rate ranges from 100-150 bpm.
If the onset of tachycardia was recorded, the absence of "warm-up" of the tachycardia cycle length makes atrial flutter the most likely diagnosis. Similarly, sudden termination of the tachycardia points to atrial flutter.
If the conduction ratio is consistently 1:1, the diagnosis is more difficult. The QRS complex may be aberrantly conducted at this rate, and ventricular tachycardia must be considered in the differential diagnosis. A 1:1 conduction ratio may produce a ventricular rate of 300 beats per minute in children, in patients with the pre-excitation syndrome, in those whose AV nodes conduct rapidly, and occasionally in patients with hyperthyroidism.
With a 2:1 conduction ratio, every other flutter wave may be hidden within the QRS complex. In this case, the electrocardiographic (ECG) findings often suggest a mild sinus tachycardia with first-degree AV block. Because adrenergic states that cause sinus tachycardia usually shorten rather than prolong the PR interval, the differential diagnosis of atrial flutter should be considered.
Assessment of heart rate or conduction ratio responses to vagal maneuvers or adenosine may be helpful.
According to one study, V1 was the most important ECG lead that aided diagnosis of the supraventricular tachycardia (SVT) mechanism; the study also reported that combining V1 with the inferior limb lead III increased the chances of identifying the SVT mechanism from 80% to 96%. [14]
In patients with possible atrial flutter occurring soon after the repair of congenital heart disease, the use of temporary atrial pacing wires is extremely helpful in diagnosis and therapy. Unipolar atrial wire recordings or bipolar recordings with a simultaneously recorded surface ECG may be used to confirm a suspected atrial flutter with 2:1 conduction ratio by unmasking the second flutter wave.
In patients without temporary atrial wires, the use of an esophageal electrode placed behind the left atrium is also extremely helpful for diagnosis and therapy. Bipolar recordings with a simultaneously recorded surface ECG can be optimized by advancing or withdrawing the electrode until the atrial electrogram is at its maximal size.
Modern atrial or dual-chamber pacemakers can provide a unipolar or bipolar atrial electrograms by telemetry from the device.
P-wave signal averaging using a specialized ECG has demonstrated some ability to differentiate adults who are likely to develop occurrences or recurrences of atrial fibrillation. This technique has been adapted to predict the occurrence of atrial flutter following the Fontan procedure.
Electrical termination of atrial flutter and additional testing can be performed through atrial wires, esophageal electrodes, permanent pacing systems, or during an intracardiac electrophysiology study. These studies may identify whether an arrhythmia is reproducibly overdriveable, and invasive testing may help identify the specific arrhythmia circuit.
Electrophysiologic Testing
Three-dimensional electroanatomical physiologic mapping of atrial arrhythmias is helpful, especially in patients who have undergone atriotomies because of the presence of multiple, extended, and/or complex reentry circuits.
The reentrant arrhythmia circuit confined to the atrial chambers may be macroscopic and mappable using standard electrophysiologic catheters or it may be microscopic and mappable only in the research laboratory using fine electrode arrays.
Postcatheterization precautions include hemorrhage, vascular disruption (if the patient underwent concomitant balloon dilation of a stenosed vessel), pain, nausea and vomiting, and arterial or venous obstruction from thrombosis or spasm. Complications may also include tachyarrhythmias or bradyarrhythmias.
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Rhythm strip depicting lead II of a patient with atrial flutter with an atrial rate of 300 beats per minute (bpm). Atrioventricular conduction rate is variable at 2:1 and 3:1. Therefore, the ventricular rate ranges from 100-150 bpm.
