Cardiac anatomical axes by CT scan and confirmation of the accuracy of fluoroscopic individualized left anterior oblique projection for right ventricular lead implantation

Abstract

Background The fluoroscopic individualized LAO (i-LAO) projection has demonstrated high accuracy for identifying right ventricular (RV) lead positioning, likely by approximating a view along the septal or RV long axes. However, RV and septal anatomical axes have not been studied, and their relation with i-LAO is unknown. We sought to determine RV, septal, and left ventricular (LV) long-axis orientations by CT scan and to compare them to the i-LAO angle, to confirm the anatomical relevance of i-LAO. Methods We prospectively included patients (pts) for whom i-LAO angle was determined during pacemaker or defibrillator implant. Then, RV, septal, and LV long-axis orientations were determined by CT scan by a physician blinded to i-LAO data. The horizontal components of the cardiac axes were compared with those of the i-LAO angle. Results We included 26 pts. Median values were 57.5° for i-LAO angle (range 47.5–70), 64.5° for RV axis (range 48–90), 51.5° for septal axis (range 39–74), and 37° for LV axis (range 25–67). i-LAO angle best correlated with septal axis (r = 0.91 and ρ_c = 0.71). Up to an angle of 70° (maximal measurable i-LAO value; 23/26 pts), the i-LAO angle was comprised between the septal and the RV axes (21/23 pts, 91.3%), or within 2° of this interval (2/23 pts, 8.7%). Conclusions RV and septal anatomical axes present major interindividual variations, prompting the use of individualized fluoroscopy criteria for lead implantation. i-LAO angle demonstrated to be almost constantly between the septal and RV long axes, thus confirming its anatomical relevance for RV lead implantation.