Atypical Flutter:

Abstract

Understanding of typical flutter circuits led the way to the study of other forms of macroreentrant tachycardias of the atria, and to their treatment by catheter ablation. It has become evident that the ECG classification of atrial flutter and atrial tachycardia by a rate cutoff and the presence or absence of isoelectric baselines between atrial deflections is not a valid indicator of tachycardia mechanism. Macroreentrant circuits where activation rotates around large obstacles are the most common arrhythmias found in patients with atypical forms of flutter or atrial tachycardia, especially after surgery for congenital heart disease, however, focal mechanisms can also be found. Large areas of low voltage electrograms, suggestive of severe myocardial damage (fibrosis or infiltration) can be found in many atypical macroreentrant tachycardias at the center of the circuit. Many of these circuits can be mapped precisely, critical isthmuses can be defined, and effective catheter ablation can be performed. The need to match activation maps with anatomy precisely, makes computer assisted, anatomically precise mapping a useful tool. Entrainment techniques have to be used sparingly to avoid tachycardia interruption. In complex cases, ablation can be done in sinus rhythm, after definition of conducting channels between low voltage areas and scars or anatomic obstacles. Long-term prognosis is uncertain and depends on the underlying pathology.

Postmitral Valve Replacement Biatrial, Septal Macroreentrant Atrial Tachycardia Developing After Perimitral Flutter Ablation

“…Perimitral atrial flutters in particular are more common in patients with a history of iatrogenic or noniatrogenic structural heart disease, yet, scar or low-voltage areas on the posterior wall of the LA as a posterior boundary of this circuit have also been described by means of electroanatomic voltage mapping in patients without obvious structural disease. 8 Another mentionable observation is the dissociation of the CS and posterior LA from the RA free wall (here during return cycle pacing in the LA aspect of the interatrial septum), a frequently seen phenomenon in patients with extensive scars after open heart surgery. 9 Nevertheless, it has to be kept in mind as a first clue that the appearance of macroreentrant circuits may not be limited to the LA, although the associated structural heart disease or related interventions are essentially left sided because the interventional access may, for example, involve the right-sided aspect of the interatrial septum.…”

Atrial Flutter, Typical and Atypical: A Review

“…ECG waveform can be determined by activation of the atrial myocardium outside the re-entry circuit 26,27 and the precise mechanism generating atypical ECG flutter patterns can only be determined by mapping and pacing EP studies. 117 Atypical flutter is often associated with structural heart disease, especially in patients that have undergone cardiac surgery or extensive catheter ablation for the treatment of AF. In these cases focal (centrifugal) mechanisms can coexist with MRT with indistinguishable ECG patterns, making EP study the only way to unveil the mechanisms causing the arrhythmia and plan ablation when clinically indicated.…”

Atrial flutter: from ECG to electroanatomical 3D mapping

“…This form is sustained by macro-re-entrant circuit in the left atrium that rotates around the mitral annulus either in counterclockwise or clockwise direction, supported by endocardial structures such as the mitral annulus anteriorly and low-voltage areas or scars posteriorly (20, 33–35). …”