Association of Rate-Dependent Conduction Block Between Eccentric Coronary Sinus to Left Atrial Connections With Inducible Atrial Fibrillation and Flutter

Abstract

Background We sought to describe the prevalence and variability of coronary sinus (CS) and left atrial (LA) myocardium connections, their susceptibility to rate-dependent conduction block, and association with atrial fibrillation (AF) and flutter (AFL) induction. Methods and Results The study cohort included 30 consecutive AF patients (age 63.3±10.5 years, 63% male). Multipolar catheters were positioned in the CS, high right atrium (HRA), and LA parallel to and near the CS. Trains of 10 pacing stimuli were delivered during sinus rhythm from each of the following sites: CS proximal (CSp), CS distal (CSd), LA septum (LAs), lateral LA (LAl), and HRA, at the following cycle lengths (CL): 1000, 500, 400, 300, and 250 ms, while recording from the other catheters. With the CS 9–10 bipole just inside the CS ostium, CS-LA connections were observed in 100% at CS 9–10, 30% at CS 7–8, 23% at CS 5–6, 23% at CS 3–4, and 97% at CS 1–2. Eighteen patients (60%) had AF/AFL induced. Rate-dependent conduction block of a CS-LA connection at CL ≥250 ms was present in 17 (94%) of those with versus none of those without AF/AFL induction (P<0.001). Conclusions Rate-dependent eccentric CS-LA conduction block is associated with AF/Flutter induction in patients with drug-refractory AF undergoing ablation. The presence of dual muscular CS-LA connections, coupled with uni-directional block in one limb, appears to serve as a substrate for single or multiple reentry beats and arrhythmia induction.

Double trouble within the coronary sinus: What is the mechanism?

“…Of note, while the patient was in SR, constant pacing at the inferior aspect of the ridge reproduced the same windshield wipers pattern seen during LAT within the CS ( Figure 3A The variability of the conduction through the CS-LA connections, related to their intrinsic conductive properties (conduction-delay), [2][3][4] explains the variable relationship between the endocardial and the epicardial activation.…”

“…1 Subsequently, elegant studies have described the electrophysiological properties of these connections as well as their potential supporting role for re-entrant tachycardias and AF. [2][3][4] Despite all these robust publications, during several years the clinical implications of these connections have been relatively neglected by the electrophysiological community. However, besides their importance in the understanding of LATs as highlighted by our observation, a recent publication has pointed out the interest of these CS-LA connections (in particular the Marshall's bundle) as potential targets for the treatment of persistent AF in humans.…”

“…The variability of the conduction through the CS‐LA connections, related to their intrinsic conductive properties (conduction‐delay), explains the variable relationship between the endocardial and the epicardial activation.…”

Sustained and self‐terminating atrial fibrillation induced immediately after pulmonary vein isolation exhibit differences in coronary sinus electrical activity from onset

“…In addition, this type of activity was associated with AF‐like ECG activity as well as AF induction. Finally, the presence of functional conduction block at CS‐LA connections along with a variable CS activation sequence has been shown in humans to be associated with AF inducibility and with a history of AF …”

Peri–coronary sinus atrial flutter associated with prior slow pathway ablation

“…In fact, atypical atrial flutter (AFL) involving the CS musculature in its reentrant circuits has been reported, 2 , 3 and some studies have suggested that reentry via the CS–LA electrical connections could contribute to the initiation and maintenance of atrial fibrillation. 4 , 5 …”