Background: CARTO merge™ is used in integrating left atrial (LA) CARTO and computed tomography (CT) images, but the integration method is not established. The relative anatomic position and configuration of the LA posterior wall (LAPW) between the right and left pulmonary veins (PVs) are not greatly affected by respiration, LA contraction or hydration state. LAPW and adjacent roof area has an anatomically curved structure which is geometrically amenable to integration using a surface registration software.
Methods: We examined the accuracy of surface registration using only the LAPW CARTO image constructed by mapping of a mean of 101 ± 34 points in 108 consecutive AF patients before PV isolation. After visual alignment of CARTO LAPW and LA CT images using one anatomically defined position in each image, the two images were integrated with an installed surface registration program. Points with differences ≥ 4.0 mm between the two images were deleted (mean, 17 points/patient) and a second surface registration was performed.
Results: The mean distance between CARTO and CT images was 1.37 ± 0.23 mm, with mean minimum and maximum values of 0.03 and 3.99 mm, respectively. The accuracy of integration was verified in 34 patients by measuring the gaps between the catheter tip on the LA wall and the design line delineated for PV isolation on the integrated image. The gaps (mm) at the superior, inferior, anterior and posterior sites on the right PV side were 0.8 ± 0.5, 0.9 ± 0.7, 1.3 ± 1.0, and 0.8 ± 0.7, respectively, and those on the left side were 0.8 ± 0.5, 0.9 ± 0.7, 1.0 ± 0.5, and 1.0 ± 0.6, respectively. Thus, the gaps were all <1.0 mm, except for the right anterior aspect.
Conclusions: These results show that surface registration using only the LAPW image can accurately integrate CARTO and CT images.