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 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: 1000, 500, 400, 300, and 250 ms, while recording from the other catheters. With the CS 9 to 10 bipole just inside the CS ostium, CS-LA connections were observed in 100% at CS 9 to 10, 30% at CS 7 to 8, 23% at CS 5 to 6, 23% at CS 3 to 4, and 97% at CS 1 to 2. Eighteen patients (60%) had AF/atrial flutter induced. Rate-dependent conduction block of a CS-LA connection at cycle length of ≥250 ms was present in 17 (94%) of those with versus none of those without AF/atrial flutter induction (P<0.001).

Conclusions: Rate-dependent eccentric CS-LA conduction block is associated with AF/atrial flutter induction in patients with drug-refractory AF undergoing ablation. The presence of dual muscular CS-LA connections, coupled with unidirectional block in one limb, seems to serve as a substrate for single or multiple reentry beats, and arrhythmia induction.

Keywords: atrial fibrillation; atrial flutter; catheter ablation; coronary sinus; myocardium.

© 2016 American Heart Association, Inc.

Figures

Figure 1

Catheter placement for pacing and recording: (A) The schematic shows the positions of decapolar, quadripolar, and duodecapolar catheters in the coronary sinus (CS), high right atrium (HRA), and left atrium (LA), respectively; additional panels show a typical case with fluoroscopic (B) left anterior oblique and (C) right anterior oblique views. HRA: high right atrium; LAs: left atrium septum; LAl: lateral left atrium; CSp: proximal coronary sinus; CSd: distal coronary sinus

Figure 2

Representative electrograms of CS trigger (A) and CS pivots (B). Panel A shows a CS trigger (blue arrow) that induced AF. Panel B displays CS pivots at CSp during LAl pacing with CL 250 ms. Note lack of electrograms on the adjacent LA catheter which confirms that the CS signals are not far-field.

Figure 3

Representative high density activation map of the LA (A) and electrograms (B) demonstrating CS-LA connections during low output distal CS pacing (CS 1–2). Panel A demonstrates 2 distinct sites of early activation in the LA overlying the distal CS and the proximal CS when pacing the distal CS at a cycle length of 900 ms. Panel B displays the earliest LA electrograms (Lasso 15,16 and 17–18 on panel A), which demonstrate delay compared to the stimulus and rule out direct LA capture. LAO: left anterior oblique; CS: coronary sinus

Figure 4

Representative electrograms of CS-LA connection at the proximal (A), middle (C), and distal (E) CS, as well as absence of CS-LA connections at the middle (B) and distal (D) CS. The annotation at the bottom of each figure indicates the pacing location and CL. Panel A shows CS-LA connections at the proximal CS with bi-directionality of the conduction. Traces from 5 separate patients are displayed in figures A through E.

Figure 5

The electrograms suggest rate-dependent conduction block of CS-LA connections followed by induction of AF (A) or AFL (B). Annotations below each tracing indicate pacing location and CL. Panel A shows pacing from the lateral LA with rate-dependent CS-LA conduction block at CS 7,8 at 250 ms followed by AFL induction and degeneration to AF within 6 beats. Panel B shows pacing from lateral LA with rate-dependent CS-LA conduction block at CS 1,2 at 250 ms, followed by AFL induction.

Figure 6

The Figure displays a representative case of CS-LA connection ablation following AF induction. Annotations at the bottom of each electrogram indicate the pacing location and CL. After RFA at the CSd-LAl, LAs activates earlier with only delayed and far-field activation of the LAl. The position of the ablation catheter is marked with a red star on the fluoroscopic image.