Atrial Flutter Workup

Electrocardiography (ECG) is essential in making the diagnosis. Transthoracic echocardiography is the preferred modality for evaluating atrial flutter.

The history and physical examination findings guide laboratory studies. Although hyperthyroidism is a rare cause of atrial flutter, asymptomatic hyperthyroidism, especially in elderly patients, can manifest as atrial fibrillation or flutter and should be excluded with thyroid function studies.

Obtain a complete blood count if anemia is suspected or the patient has a history of recent or current blood loss associated with presenting symptoms. Serum electrolytes and pulmonary function tests may be indicated based on the history. Obtain serum electrolyte and digoxin levels if appropriate.

Consider obtaining blood gas measurements in patients with hypoxia or carbon monoxide intoxication. Also, seek a history of stimulant drug usage (eg, ginseng, cocaine, ephedra, methamphetamine).

Chest radiography may be useful in evaluation of lung disease and the pulmonary vasculature. Chest radiographic findings are usually normal in patients with atrial flutter, but radiographic evidence of pulmonary edema may be present in subacute cases.

In the common form of type I atrial flutter, the ECG shows sawtooth flutter (F) waves. Flutter waves are often visualized best in leads II, III, aVF, or V₁ (see the image below). The flutter waves for typical (type I) atrial flutter are inverted (negative) in these leads because of a counterclockwise re-entrant pathway. Sometimes, they are upright (positive) when the re-entrant loop is clockwise. Flutter waves (particularly 2:1) can deform the ST complex in such a manner as to mimic an ischemic injury pattern on the 12-lead ECG.

In typical (ie, type I) atrial flutter, the atrial rate is usually 250-350 beats per minute. The ventricular response may be regular or irregular. In patients with typical (ie, type I) atrial flutter, class IA and IC antiarrhythmic drugs and amiodarone can reduce the rate to approximately 200 beats per minute. If this occurs, the ventricles can respond in a 1:1 fashion to the slower atrial rate. The rate in atypical (ie, type II) flutter is 350-450 beats per minute.

The ventricular rate is a fixed mathematical relationship of flutter waves and the resulting QRS complexes. Variable AV conduction can also be seen (commonly present with 2:1 or 3:1 AV conduction). With 1:1 AV conduction, hemodynamic collapse may occur.

Deterioration to 1:1 conduction is a particular risk in patients with a preexcitation syndrome (Wolff-Parkinson-White). An ECG clue to a preexcitation syndrome is a very short PR interval (< .115s) and no delta wave.

Morphology of the flutter wave can predict findings in the electrophysiology laboratory. A negative flutter wave in the inferior limb leads and a positive flutter wave in V₁ are highly predictive of a counterclockwise circuit; however, with positive flutter waves in the inferior limb leads and negative flutter waves in V₁, differentiating between clockwise type I atrial flutter and atypical forms of non–isthmus-dependent intra-atrial reentry is difficult.

Flutter and fibrillation often coexist with alternating patterns (ie, fib-flutter, flitter) in the same tracing.

Vagal maneuvers can be helpful in determining the underlying atrial rhythm if flutter waves are not seen well.

Adenosine, administered in an intravenous push followed with an intravenous bolus with flush, can also be helpful in making the diagnosis of atrial flutter by transiently blocking the AV node (see the image below).

Exercise testing can be utilized to identify exercise-induced atrial fibrillation and to evaluate ischemic heart disease.

A Holter monitor can be used to help identify arrhythmias in patients with nonspecific symptoms, identify triggers, and detect associated atrial arrhythmias.

Transthoracic echocardiography is the preferred modality for evaluating atrial flutter. It can evaluate right and left atrial size, as well as the size and function of the right and left ventricles, which assists in diagnosing valvular heart disease, left ventricular hypertrophy (LVH), and pericardial disease.

Transthoracic echocardiography has low sensitivity for intra-atrial thrombi. Transesophageal echocardiography is the preferred technique to detect thrombus in the left atrium.