Identification of Functional Block Line in Atrial Flutter Using Three-Dimensional Intracardiac Echocardiography

Electrophysiologic and Anatomical Characteristics of the Right Atrial Posterior Wall in Patients With and Without Atrial Flutter Analysis by Intracardiac Echocardiography

“…Both recent studies [14][15][16][17][18] and the present study results strongly support the transverse conduction block at the sinus venosa region. However, the present study showed no site difference of the conduction block in that region between the AFL and control patients.…”

“…[4][5][6] Most former studies assumed that the localization of the transverse conduction block was the CT in AFL patients. [4][5][6][7][8][9] However, more current studies [14][15][16][17][18] using ICE or noncontact mapping systems have concluded that the conduction block occurred at the posteromedial RA (sinus venosa region) rather than on the CT. The present study also showed that the DP recording site observed in the AFL patients was located at the posterolateral RA adjacent to the posterior edge of the CT or posteromedial RA.…”

“…[4][5][6][7][8][9] This is critical for the induction and maintenance of AFL, as it prevents the flutter wave from "short-circuiting" across the posterior RA. However, several recent studies have suggested that the CT may not be a consistent barrier to conduction in AFL; some studies showed the presence of a posteromedial functional block in the sinus venosa region, but not on the CT, using intracardiac echocardiography (ICE); [14][15][16] other studies showed double lines of block during AFL, with the first line located along the CT area and the second line located in the sinus venosa region. 17,18 The aim of this study was to delineate the posterior boundary in the RA and compare the block line in terms of functional and fixed components and the anatomical structures in patients with and without AFL using 2-and 3-dimensional (2D, 3D) ICE.…”

Action Potential Characteristics in the Sinus Venosa of Patients With and Without Atrial Flutter

“…[8][9][10] Several studies have shown the presence of a functional line of block in the posteromedial RA, the sinus venosa (SV) region, as an alternative. [11][12][13][14][15] The SV is a smooth-walled structure and has no grossly distinguishable structural barriers, but there are abrupt changes in the thickness and orientation of the muscle fibers, as well as in the collagen content. 16,17 Such microscopic discontinuities have been suggested to provide a basis for rate-dependent conduction block during transverse atrial activation.…”

The Undetermined Geometrical Factors Contributing to the Transverse Conduction Block of the Crista Terminalis

“…cause functional transverse conduction block during AFL or rapid pacing. [8][9][10][11][12] A line of transverse conduction block along the CT serving as a lateral boundary can be determined by the presence of double and split potentials recorded during AFL or rapid pacing from either side of the CT during an electrophysiologic (EP) study. [5][6][7] Anatomically, the CT can be recognized as a convex ridge, which spans from the anterior RA to the superior vena cava (SVC), then to the inferior RA and posteriorly to the inferior vena cava (IVC), and in some subjects it extends toward the Eustachian ridge/valve through the posterior RA.…”