The Variable Arrangement of the Atrioventricular Conduction Axis Within the Triangle of Koch: Millimeters Matter

Anatomical characteristics of the membranous septum are predictive of pacemaker requirement in patients undergoing transcatheter aortic valve replacement

PURPOSE

We aimed to study the characteristics of the membranous septum (MS) and its relationship with the aortic valve (AoV) and aortic annulus (AA) in patients who required PPM post-TAVR.

METHODS

We performed a retrospective case-control study of 144 patients undergoing TAVR from 2016 to 2018. Thirty-four patients, requiring PPM implantation, were compared with 34 matched controls who did not require pacing. The total MS length, supra-annular MS (SA-MS) length, infra-annular MS (IA-MS) length, angle between the plane of the AA and MS (AA-MS), and degree of AoV calcifications (AVC) were obtained from preoperative CT. AoV prosthesis implantation depth was obtained from intra-operative fluoroscopy.

RESULTS

There were no significant differences in valve type (self-expandable: 23 cases vs 25 controls, and balloon-expandable: 11 vs 9, p = 0.79), degree of AVC (0.65 cm³ vs 0.82 cm³, p = 0.62), or implantation depth (7.76 mm vs 7.28 mm, p = 0.83). Compared to controls, there was no difference in total MS length (6.68 mm vs 6.06 mm, p = 0.97), but the IA-MS was significantly shorter (3.64 mm vs 4.56 mm, p = 0.02) and the SA-MS was significantly longer (2.73 mm vs 1.67 mm, p = 0.02) in patients requiring PPM. Patients requiring PPM also had a larger AA-MS angle (103.5° vs 96.7°, p = 0.01).

CONCLUSION

The position of the MS with respect to the AA and MS distance below the annular plane were more closely associated with post-TAVR conduction abnormalities requiring PPM than the absolute length of the MS. Patients undergoing TAVR with such anatomy have a higher risk of requiring PPM and should be monitored for developing these complications.