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Characterization of the anatomy and conduction velocities of the human right atrial flutter circuit determined by noncontact mapping

Richard J. Schilling, MD^a, Nicholas S. Peters, MD^a, Jeffrey Goldberger, MD, Alan H. Kadish, MD and D. Wyn Davies, MD^a

^a St. Mary’s Hospital and Imperial College School of Medicine, London, United Kingdom
Northwestern Memorial Hospital, Chicago, Illinois, USA

View larger version (146K): [in a new window]   Figure 1 A posterio-anterior radiograph showing the multielectrode array (B) canted toward the tricupsid annulus by a guide wire passed out through the right ventricular outflow tract, so that the multielectrode array pigtail is straightened in the ventricle. Also seen are catheters in the high right atrium (RA), right ventricular apex (RVA), His bundle (His), coronary sinus (CS) and a mapping/ablation catheter on the tricupsid annulus-inferior vena cava isthmus (Map).

View larger version (78K): [in a new window]   Figure 2 (A) Unipolar isopotential maps recorded from the right atrium (RA) during clockwise atrial flutter. The virtual endocardium has been cut and unfolded along the anterior border of the tricupsid annulus (TA), and the two edges are in continuity from top to bottom showing the concave inside surface of the endocardium. Even when this "open view" of the RA is shown, the system attempts to provide some perspective, and the virtual endocardium has been turned so that the lateral RA wall is seen in detail while the septum and isthmus are foreshortened. Anatomical locations have been identified using fluoroscopy and contact electrograms and marked in yellow on the virtual endocardium as follows: SVC = superior vena cava; IVC = inferior vena cava. The blue lines drawn on the lateral wall and above the CS os represent the probable position of the crista terminalis (CT) and eustachian ridge (ER) as defined by lines of conduction block to wave front propagation. The voltage range displayed on the isopotential map has been narrowed so that the map becomes equivalent to an activation map with unipolar activation (negative voltage) displayed as a colored region. Activation is validated by examination of individual electrograms, thus ensuring that noise artefact is excluded. The positions of the reconstructed bipolar electrograms (displayed in A) are labeled a to f from superior to inferior along the blue line, indicating a line of conduction block and the possible position of the CT. Activation is displayed on the virtual endocardium as a white and colored area. Activation (white and colored region) is seen progressing from the anterolateral RA near the IVC (frame 1) to the superior anterolateral RA (frames 2 and 3) along a line of block. Activation then turns at the SVC and progresses down the opposite side of the line of block from superior to inferior (frames 3 to 5) before it reaches the IS. Activation progresses through the IS (frame 6 to 1), before activation of the anterolateral RA occurs again (frame 1). (B) Reconstructed bipolar electrograms during two atrial flutter cycles are shown, from positions a to f along a line of block as shown in B. The numbers 1 to 6 indicate the time point from where the isopotential maps (A) were taken. Electrograms show double potentials with the isoelectric interval increasing from a to f. The long interval between the second potential on electrogram f and the first potential on the subsequent electrogram reflects the time for activation to pass through the IS.

View larger version (94K): [in a new window]   Figure 3 (A) Unipolar isopotential maps recorded during counterclockwise atrial fluter. The endocardium is opened, unfolded and flattened, resulting in stretching of the anterolateral right atrium (RA) (spread grid-lines) and compression of the posteroseptal wall (packed grid-lines). The positions at which bipolar electrograms have been reconstructed and displayed in B are labeled as a to e from superior to inferior along a line of block, compatible with the position of the crista terminalis (CT). Activation passes through the tricupsid annulus-inferior vena cava isthmus (frame 1) and turns toward the tricuspid annulus (TA) (arrow) around a line of block (possibly the eustachian ridge [ER]) (frame 2). The wave front the then begins to split (frame 3) with one front moving superiorly along the line of block while the second front moves slowly along the ER. The first wave front turns at the superior vena cava (SVC) (frame 4) and then passes inferiorly along the line of block (frames 5 and 6). The second front passes slowly through a break in the line of block (frames 4 to 6). The first and second wave fronts then fuse (frame 7), pass around the inferior vena cava (IVC) to enter (frame 8) and pass through the IS (frame 1). (B) The surface electrocardiographic lead II, an electrogram from a catheter at the coronary sinus os and reconstructed bipolar electrograms from points a to e on the isopotential maps in A. The numbers 1 to 8 represent the points at which the isopotential maps have been displayed in A. The electrograms from the line of block show double potentials apart from those recorded at the break in the line of block, which are long and fractionated, representing the slow activation at this point.

View larger version (109K): [in a new window]   Figure 4 Isopotential maps with the lateral wall of the right atrium (RA) removed so that the virtual endocardium shows the septum (Sept), tricuspid annulus-inferior vena cava (IVC) isthmus (IS) and tricuspid annulus (TA) in detail and the reader is looking in toward the TA. The possible position of the eustachian ridge is drawn onto the virtual endocardium as a yellow line. The atrial flutter wave front enters and passes through the IS (frame 1) and encounters a line of block at the posterior IS. The wave front turns toward the TA (arrow), passes up over this line of block and back down the posterior aspect of the line of block (frames 2 and 3). The wave front exits the posterior RA (frames 3 to 4). The posterolateral RA activates before the TA as does the anterior RA (frames 4 to 6). Activation then progresses from both areas toward the TA where the wave front(s) extinguish. The anterolateral wave front then passes into the anterior IS and through the IS to repeat the circuit (frame 6 to 1). Ant - anterior; cs = coronary sinus; His = His bundle; SVC = superior vena cava.