Catheter Ablation -> Ventricular Arrhythmias -> Mapping & Imaging D-PO06 - Poster Session VI (ID 26) Poster

D-PO06-101 - Influence Of Pacemapping Rate On QRS Morphology Matching: Proof And Recognition Of The “TR Fusion” Phenomenon (ID 663)


Background: Pacemapping is used to identify exit sites during scar related ventricular tachycardia (VT) mapping with aid of automated scoring from commercial electroanatomic mapping systems. The influence of paced cycle length (CL) on pacematching has not been systematically assessed.
Objective: To assess and quantify differences in pacemap score when paced within scar at various CLs compared to the CL of VT.
Methods: We prospectively pacemapped from local abnormal ventricular electrograms starting at CLs of 600 (or shorter than underlying sinus rate) and decrementing by 100 ms up to within 20 ms of the VT CL. An automated score between 0 to 100, with 100 being a perfect match (Ensite, Precision, Abbott), was recorded at all pacemap rates and analyzed.
Results: In 27 patients, pacemaps were obtained from 51 distinct sites to match 31 distinct VTs (median VT CL 300 ms). Median pacemap match score for 600 ms, 500 ms, 400 ms, 300 ms and VT CL +/- 20ms were 85, 84, 88, 88 and 90. Median difference between the lowest and the highest score when paced at various CL at the same site was 7 (range 0-27). In all cases, QRS onset appeared slurred at faster paced CL. Figure 1 illustrates progressive improvement in automated pacematch score with subsequent change in the QRS onset with endocardial pacing closer to the VT CL. Superimposition of the preceding T wave into QRS onset (TR fusion) slurs the QRS onset fulfilling epicardial VT criteria.
Conclusion: The rate of pacemap can alter automated scoring by 7% in scar-related VTs, where paced CL closer to VT yields higher score. Faster pacing resulting in TR fusion confounds the onset of QRS. This may explain the poor discriminatory power of epicardial criteria in scar-related VT.