Background: Two common catheters used for substrate mapping during catheter ablation of ventricular tachycardia include the PentaRay and Thermocool catheters (Biosense-Webster, Diamond Bar, CA). The former has a smaller bipole consisting of 1 mm electrodes and 4 mm spacing while the latter has a larger bipole consisting of a tip 3.5 mm electrode and proximal 2 mm electrode separated by 3.5 mm.
Objective: To characterize the difference in myocardial “field of view” of different mapping catheters based on contrast-enhanced cardiac computed tomography (CE-CT).
Methods: Electroanatomic mapping (EAM) performed during baseline rhythm in 15 patients undergoing catheter ablation of post-infarct VT was registered to pre-procedure CE-CT. The average myocardial attenuation density within varying radii (2 mm, 5 mm, 10 mm, 15 mm) from each EAM point was measured using MATLAB (Natick, MA) excluding points in regions of artifact. Voltage was log transformed to adjust for skew. The association between endocardial voltage and attenuation density was assessed using a multi-level random effects linear regression model, clustered by patient, with best model fit defined by highest log-restricted likelihood (LRL).
Results: A total of 3,850 and 846 points were obtained with a PentaRay and Thermocool catheter respectively. With a Thermocool catheter, there was a significant association between bipolar voltage and attenuation density at all analysis radii (p < 0.05) with best model fit at a radius of 15 mm (0.94 per 100 HU; 95% CI 0.72, 1.17; LRL -1035.35). With a PentaRay catheter, there was a significant association between bipolar voltage at all analysis radii (p < 0.05) with best model fit at a radius of 5 mm (0.42 per 100 HU; 95% CI 0.28, 0.55; LRL -3207.71). For both, there was a significant association between unipolar voltage and attenuation density (p<0.05) with best model fit at an analysis radius of 15 mm (Thermocool 0.72 per 100 HU; 95% CI 0.59, 0.85; PentaRay: 0.46 per 100 HU; 95% CI 0.38, 0.54).
Conclusion: The association between endocardial electrogram measurements and myocardial attenuation density on CE-CT varies based on mapping catheter. The smaller bipolar electrode configuration of the PentaRay catheter is associated with a smaller myocardial field of view.