Catheter Ablation -> Ventricular Arrhythmias -> Electrocardiography D-PO06 - Poster Session VI (ID 26) Poster

D-PO06-079 - Q -wave At Ablation Site Of Focal Ventricular Arrhythmia Source: Dogma Shattered (ID 1353)

Abstract

Background: When mapping focal ventricular arrhythmia (FVA), negative monophasic QS wave on ablation unipolar electrograms (Uegms) is used as confirmation of proximity to source. This dogma is derived from biophysical principles that posits that recordings close to a FVA shall only see electrical activity propagating away and generating a QS wave. Recently this precept has been challenged by clinical experience, however this has not yet been tested in controlled experiments, especially with depth of intramural FVA.
Objective: We tested the hypothesis that QS-Wave will be recorded at close proximity of focal source ablation site and as the source is located more intramurally it will become a poor predictor of focal source proximity.
Methods: A FVA was simulated in 7 swine hearts in a Langendorff model by plunging stimulating electrode (SE) to varying depths of 1, 2, 3, & 4 mm while mapping with a 56-electrode array positioned on the epicardium of the LV freewall . Uegms were recorded for each depth of pacing and QS and r-wave were detected with a custom Matlab program. Binary maps depicting absence or presence of QS-wave were produced. Computer simulations from a realistic Human hearts using CARP software with similar stimulation and recording conditions were also performed.
Results: When the FVA was epicardial/sub-epicardial QS patterns were recorded as far as 7mm away. Mapping data demonstrated QS waves at edge of the mapping field, suggesting the zone of QS was further away than the furthest 7 mm recorded. QS waves were present in almost half (48%) of the recorded Uegms. This corresponded to an averaged surface of 8 x 8 mm. These results were similar at different SE depths. Simulation studies confirmed the experimental findings with areas devoid of r-wave exceeding 76 mm2 and also possibly exceeding the mapping field.
Conclusion: QS waves are poor indicator to proximity to FVA and are also poor predictor of depth of source when mapping FVA in the ventricle. Using the presence of QS on Uegms as confirmation of proximity to source when mapping using LAT is unfounded. These findings challenges our pre-conceived notion of travelling wave effects on Uegms that could possibly be explained by the complex anisotropy and myocardial mass electromotive force on Uegms recorded in the ventricle.
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