Effects of Gap Geometry on Conduction Through Discontinuous Radiofrequency Lesions

Abstract

Background— Gaps of sufficient cross-sectional dimensions within linear radiofrequency (RF) lesions may allow conduction through the lesion. The purpose of this study was to examine the effects of different gap geometries on conduction through discontinuous RF lesions. Methods and Results— Radiofrequency lesions were created in isolated, perfused rabbit right ventricular (RV) free wall preparations to produce gaps with 3 different lesion geometries: straight, bifurcated, and angled (n=10 each group). Angled preparations contained 2 right angles within the conduction path. Optical mapping was used to assess bidirectional conduction through the myocardium before and after gap formation during pacing at 1000-, 400-, and 200-ms cycle lengths. Histological analysis was performed on each preparation after optical mapping. After lesion formation, 9 of 10 straight gap preparations and 1 of 10 angled gap preparations demonstrated bidirectional conduction ( P <0.001) at all cycle lengths. Nine of 10 bifurcated gap preparations demonstrated bidirectional conduction and 1 demonstrated unidirectional conduction at all cycle lengths. Two bifurcated gap preparations showed rate-dependent unidirectional 2:1 conduction. All unidirectional and rate-dependent block occurred during impulse propagation in the direction of diverging arms of the bifurcation. The occurrence of bidirectional conduction in the gaps was associated with the gap geometry ( P <0.0001). Histological analysis confirmed the continuity of viable myocardium transmurally throughout the length of the gap in each preparation. The sites of conduction block were demonstrated to be just after the first angle in the conduction path for angled gaps and at the branch point of a bifurcated gap. The predominant myofiber orientation was changed relative to the conduction path at angulations of the gaps. Flecainide (0.1 μmol/L) produced bidirectional conduction block in straight and bifurcated gap preparations with bidirectional conduction at baseline. Conclusions— Conduction through discontinuities in RF lesions is associated with gap geometry. Complex gap geometry may allow for unidirectional and/or rate-dependent block. Gaps within RF lesions are susceptible to pharmacological blockade.

Use of endogenous NADH fluorescence for real-time in situ visualization of epicardial radiofrequency ablation lesions and gaps

“…If implemented clinically, it has the potential to shorten the time and improve the efficiency of ablations, minimize unnecessary tissue injury that may cause post-RFA complications, and decrease postablation recurrence of arrhythmias. fNADH imaging may also be useful for mechanistic studies of tissue injury near the RFA sites (28) and for assessment of drugs that may alter electrical propagation between interlesion gaps (27). We also believe that NADH fluorescence could be potentially very useful in identifying the ablation gaps seen after pulmonary vein isolation procedures.…”

Autonomous Control of Continuum Robot Manipulators for Complex Cardiac Ablation Tasks

“…(1) Ablating tissue requires contiguous lesions to be made such that erroneous electrical pathways causing tissue fibrillation are isolated from healthy tissue [4], (2) controlling contact forces with tissue during an ablation is required to avoid perforation, (3) catheter positions are continuously disturbed by the heartbeat in unpredictable ways, and (4) sub-optimal visualizations involving electro-anatomical mapping [5] and fluoroscopy [6] challenge clinicians to perform complicated three-dimensional (3D) ablation tasks, generating significant mental and physical fatigue.…”

Electrogram-Gated Radiofrequency Ablations With Duty Cycle Power Delivery Negate Effects of Ablation Catheter Motion

“…Without being able to predict a consistent lesion length as seen in gated ablations, it is extremely difficult to achieve a contiguous line of radiofrequency ablation lesions with no gaps in between lesions that are transmural. [20][21][22][23] For a given duration and power of ablations, lesion length created was highly variable and because we often have no means of quantifying or predicting the amount of catheter sliding motion occurring at any time point, lesion length is, therefore, unpredictable depending on the catheter sliding distance occurring at the time of lesion creation. Wider than expected lesions could potentially lead to unwanted radiofrequency energy delivery to structures, such as the AV node, conversely, thinner lesions may be more conducive to interlesion gaps leading to reconnections.…”