New Insights Regarding the Atrial Flutter Reentrant Circuit

Abstract

Background-We studied atrial activation during induced atrial flutter in the canine sterile pericarditis model to test the hypothesis that the atrial flutter reentrant circuit includes a septal component. Methods and Results-We studied 10 episodes of induced, sustained (Ͼ5 minutes) atrial flutter in 9 dogs. In all episodes, the reentrant circuit included a septal component. In 6 episodes, there were 2 reentrant circuits, one in the right atrial free wall and the second involving the atrial septum, Bachmann's bundle, and the right atrial free wall; both circuits shared a pathway in the right atrial free wall (figure-of-eight). The direction (superior or inferior) of the septal wave front of the second circuit correlated with the direction (clockwise or counterclockwise, respectively) of the right atrial free-wall circuit. A line of functional block in the right atrial free wall was part of both reentrant circuits. In the other 4 atrial flutter episodes, only 1 reentrant circuit was present, with activation in an inferior-to-superior direction in the septum and a superior-to-inferior direction in the right atrial free wall in 2 episodes and in the opposite direction in the other 2 episodes. In all atrial flutter episodes, the flutter wave polarity in ECG lead II was determined by the direction of activation in the left atrium; polarity was positive when the direction was superior to inferior and negative when the direction was inferior to superior. Conclusions-In this model of atrial flutter, the reentrant circuit (1) always included a septal component, (2) did not always require a right atrial free-wall reentrant circuit, (3) demonstrated figure-of-eight reentry when a reentrant circuit was present in the right atrial free wall, and (4) was associated with a line of functional block in the right atrial free wall.

Termination of a tachyarrhythmia by flunarizine is not a specific marker for a triggered mechanism

“…The functional line of block initially failed to develop, presumably because of the still present effect of flunarizine. This "failure" again confirms, in yet another scenario, the importance of the development of a line of functional block between the venae cavae during atrial fibrillation in order to achieve and maintain classical, right atrial, macroreentrant AFL (19,21).…”

“…a failed attempt to induce AFL. The key finding was absence of development of a stable line of block between the venae cavae in the right atrial free wall, the latter being required for initiation and maintenance of the AFL reentrant circuit (19,21). A stable line of block did form after completion of the pacing induction protocol prior to flunarizine administration, resulting in sustained AFL.…”

“…The specificity of flunarizine for discriminating triggered from reentrant tachyarrhythmias has not been confirmed in atrial tachyarrhythmias, although it has been used in this manner to help establish a triggered mechanism for induced atrial tachycardia in a canine heart failure model (16). Induced AFL in the sterile canine pericarditis model is a well characterized, macroreentrant tachyarrhythmia (17)(18)(19)(20)(21). We tested the hypothesis that flunarizine would not terminate AFL in this model.…”

Non-contact mapping to guide radiofrequency ablation of atypical right atrial flutter

“…The atrial figure-of-eight re-entry has been described in the canine sterile pericarditis model (20,21). Schoels et al (20) demonstrated that 2 of 11 dogs (4 episodes) showed double-loop re-entry during sustained AFL.…”

Mechanisms of Atrial Flutter —From MacWilliam in 1887 to Miyauchi in 2005—

“…These authors using 372 unipolar electrodes arranged in 186 bipolar pairs concluded that AFL was caused by a reentrant excitation that always included a septal component, did not always require a right atrial free wall reentrant circuit and was associated with a line of functional conduction block in the right atrial free wall. 16,26) The tricuspid ring annulus was not the primary site of rotation during AFL in Waldo's model. These authors further showed that that a positive flutter wave in ECG lead II (counterclockwise circus movement) was associated with early activation of the Bachmann's bundle region compared with the posteroinferior left atrium and a negative flutter was associated with the early activation of the posteroinferior left atrium compared with Bachmann's bundle and activation of a considerable portion of the left atrium in an inferosuperior direction (clockwise circus movement).…”