Site-Specific Influence of Transversal Conduction Across Crista Terminalis on Recognition of Isthmus Block

Ultrahigh resolution electroanatomical mapping of the transverse conduction of the right atrial posterior wall in cases with and without typical atrial flutter

INTRODUCTION

The right atrial posterior wall (RAPW) is known to form a conduction barrier during typical atrial flutter (AFL). We evaluated the transverse conduction properties of RAPW in patients with and without typical AFL using an ultrahigh resolution electroanatomical mapping system.

METHODS AND RESULTS

This study included 41 patients who underwent catheter ablation of AF, typical or atypical AFL, in whom we performed RAPW mapping with an ultrahigh resolution mapping system during typical AFL and coronary sinus ostial pacing with three different pacing cycle lengths (PCLs) (1) PCL1: PCL within 40 ms of the AFL cycle length in patients with typical AFL or 250-300 ms for those without, (2) PCL2: 400 ms, (3) PCL3: PCL just faster than the sinus rate. Local RAPW conduction block was evaluated by propagation mapping and local double potentials separated by an isoelectric line. The functional block was defined as areas blocked during shorter PCLs but conductive during longer PCLs. The degree of blockade was calculated by dividing the blocked length by RAPW length (%blockade). Only two patients demonstrated a fixed complete RAPW block (100%, %blockade). Thirty-one patients demonstrated a partial block of RAPW, and the %blockade during PCL1-3 was 49.4 ± 19.8%, 39.5 ± 19.2%, and 35.0 ± 22.9% in this group, respectively. Functional block areas were frequently observed above the fixed block area adjacent to the RA-inferior vena cava junction. Transverse conduction block was more frequently observed in patients with typical AFL at any longitudinal level of RAPW.

CONCLUSION

RAPW transverse conduction block is lower-side dominant and greater in patients with typical AFL than those without.

Pseudoblock of cavotricuspid isthmus via detouring gap conduction

To detect detouring gap conduction, as demonstrated in this case, 3-D mapping is useful in addition to conventional methods.

Crista Terminalis as the Anterior Pathway of Typical Atrial Flutter: Insights from Entrainment Map with 3D Intracardiac Ultrasound

BACKGROUND

The precise location of truly active reentry circuits of typical atrial flutter (AFL) has not been well identified. The purpose of this study was to verify our hypothesis that the posterior block line is located along the posteromedial right atrium (PMRA) and the crista terminalis (CT) is the anterior pathway of AFL, with real-time intracardiac echo (ICE).

METHODS

The entire right atrium (RA) three-dimensional activation and entrainment mapping were evaluated during AFL in 18 patients using CARTO sound.

RESULTS

The CT was clearly visualized by ICE and the local electrograms along the CT were single potentials in all the patients. The CT was recognized as the truly active anterior pathway based on entrainment mapping in all patients. Double potentials were recorded along the PMRA. Entire RA entrainment mapping could be performed in 16 patients. The reentry circuits were separated into three passages. The first was around the tricuspid annulus (TA), the second the anterior superior vena cava (SVC; AFL waves passed between the anterior SVC and RA appendage), and the last the posterior SVC (between the posterior SVC and upper limit of the PMRA). All three of these passages were active in four, around the TA and anterior SVC in eight, around the TA and posterior SVC in three, and around only the anterior SVC in one patient.

CONCLUSIONS

The CT functions as the anterior pathway of typical AFL, and the posterior block line was located along the PMRA. Dual or triple circuits were recognized in the majority of AFL patients.

The undetermined geometrical factors contributing to the transverse conduction block of the crista terminalis

BACKGROUND

The crista terminalis (CT) is known to be a functional barrier during typical atrial flutter (AFL). The relationship between the CT structural characteristics and its transverse conduction block, however, has not been understood well.

METHODS

This study consisted of AFL (group 1, N = 15) and non-AFL patients (group 2, N = 13). The CT structural characteristics were determined with intracardiac echocardiography. A 20-pole electrode catheter was located along the CT and pacing at progressively faster rates from either low anterolateral right atrium (LRA) or coronary sinus (CS) was applied.

RESULTS

The CT height, width, and area were significantly greater in group 1 than in group 2 (P < 0.001). In both groups, at the longest pacing cycle length during CS pacing resulting in CT transverse conduction block at some levels, the width and area were significantly greater at the levels with block than at those without block. During LRA pacing, the area was also significantly larger at the levels with block than at those without in group 1, but not in group 2. The slope angle of CT ridge was significantly steeper at the levels with block than at those without in both groups (P < 0.01), but that was not the case with CS pacing. CT arborization in its inferior portion was more frequently documented in group 1 than group 2 (P < 0.05).

CONCLUSIONS

The CT structural characteristics that may influence its transverse conduction differ between LRA and CS pacing. Steep slope and arborization of the CT are implicated as a geometric factor in its transverse conduction block.

Activation patterns and conduction velocity in posterolateral right atrium during typical atrial flutter using an electroanatomic mapping system

BACKGROUND

To investigate the activation patterns and conduction velocity (CV) in the posterolateral right atrial (RA) wall during typical counterclockwise atrial flutter (AFL) using an electroanatomic mapping system.

METHODS AND RESULTS

During typical AFL in 25 patients, the transverse conduction pattern and CV were classified and calculated. The line blocking transverse conduction was defined by the conduction pattern and double potentials recorded during mapping. There were 3 types (including 2 subtypes) of transverse conduction pattern based on the conduction blocks across the posterolateral RA in a line between the superior and inferior venae cava. Trans-cristal conduction activation in a horizontal direction was seen in all but 4 patients. The CV in the gap area was 0.59+/-0.21 m/s.

CONCLUSIONS

Three types of transverse conduction pattern were observed during trans-ctristal conduction and the trans-ctristal CV was relatively slower than that in other parts of the RA, except for the isthmus.