Using Intracardiac Catheter Recordings from the His and Proximal Coronary Sinus to Distinguish Isthmus Conduction Block During Catheter Ablation of Type I Atrial Flutter

Abstract

Isthmus conduction block, demonstrated with the use of multipolar catheter recordings, is considered the preferred endpoint for ablation of type I atrial flutter. This study investigated the feasibility of using recordings from the His and coronary sinus (CS) to document isthmus conduction block. Isthmus conduction block was produced with linear radiofrequency (RF) ablation in 27 patients with type I atrial flutter. In 13 patients (group I), RF was delivered until bidirectional isthmus conduction block was demonstrated with multipolar Halo catheter recordings. In 14 patients (group II), RF was delivered during pacing from the lateral isthmus at 600 ms until a reversal in activation of the proximal CS and His occurred. At this point, data from the Halo recordings were reviewed to see if reversal correlated with conduction block; if not, further ablation was performed until block was demonstrated. The initial reversal in His and CS activation during RF energy delivery correlated with isthmus block in only 4 (28.6%) of 14 patients in group II. Additional RF delivery produced isthmus block in the other ten patients resulting in a further increase in the St-CS interval of 35 +/- 20 ms. A His-CS interval of at least -40 ms signified isthmus block with a sensitivity and specificity of 48% and 100%, respectively. Reversal in His-CS activation during pacing from the lateral margin of the isthmus is not specific for the creation of isthmus block. While activation of the proximal CS bipole > 40 ms after activation of the His appears specific for isthmus block, the low sensitivity of this finding limits its clinical use.

Incremental His-To-Coronary Sinus Maneuver

“…In contrast, the atrial signal registered in the Hisbundle region is secondary to conduction of the stimulus through the anterior and anteroseptal aspect of the tricuspid annulus. After CTI ablation, counterclockwise conduction is interrupted at the CTI level during pacing from the LLRA, and activation would be expected to travel sequentially from His to CSO, with a His-to-CSO EGM interval that has been reported of >40 ms. 5 We hypothesized that, in the presence of slow conduction and functional CTI block after ablation, the His-to-CSO interval would significantly increase (≥10 ms) in response to IP from the LLRA. Conversely, during complete CTI conduction block, the His-to-CSO interval should not significantly vary (<10 ms) during incremental LLRA pacing (Figures 1 and 2).…”

“…1,2 Documentation of complete transisthmus conduction block after ablation has been proven to be superior to cardioversion in terms of arrhythmia recurrence, and has become the gold-standard end point during AFL ablation. [1][2][3][4][5] However, definite proof of complete conduction block is not always evident. Distinction from incomplete block with slow conduction across the CTI is essential to achieve a favorable arrhythmia control outcome after ablation.…”

Prospective evaluation of a simplified approach for common atrial flutter radio frequency ablation with only two catheters

“…This interval is composed of atrial, nodal and His-Purkinje conduction. Some data from papers on inferior isthmus ablation [5,21,22] failed to show significant prolongation in stimulus to atrial depolarization at the His during pacing at low lateral right atrium after block. In preliminary work from our laboratory [23] we showed that the increment of S-QRS was induced by an increment of the nodal conduction time (A-H increment).…”

Incremental Pacing for the Diagnosis of Complete Cavotricuspid Isthmus Block During Radiofrequency Ablation of Atrial Flutter

“…1,2 Proof of complete transisthmus conduction block after ablation, with a detour around the ablation line of the atrial activation between the septal and low lateral right atrium (LLRA), is superior to termination of AFL during ablation and has become the goldstandard endpoint for flutter ablative therapy. [1][2][3][4][5][6] However, AFL recurrences still occur and, in addition, definite proof of complete conduction block is not always trivial. Additional local electrogram-based criteria rely on the observation of a complete corridor of parallel double potentials (DPs) along the damaged isthmus ablation line with little variation in the duration of the isoelectric line between them.…”

“…In the setting of an intact CTI, typical AFL cycle length ranges from 230 to 250 ms. [3][4][5]7,8 Pacing from either the CS or the LLRA at rates approaching the AFL cycle length may result in slow conduction and finally functional unidirectional CTI block, thus initiating typical AFL. 13 In the setting of a damaged isthmus line during CTI ablation, the documentation of DPs may represent either an increased conduction time across the CTI (with conduction gaps somewhere else in the line) or a complete line of block.…”