BACKGROUND LANDMARK was a multicenter randomized trial that demonstrated noninferiority of the Myval balloon-expandable trans. catheter heart valve (THV) compared with the contemporary THVs (Sa- pien and Evolut series) at 30 days in patients with severe aortic stenosis. METHODS From January 2021 to December 2023, 768 patients were randomized in a 1:1 ratio to receive either the Myval or a contemporary THV. This substudy investigated the conduction disturbances and rates of new permanent pacemaker implantation (PPMI) after THV implantation in detail. An independent core lab (CERC, Massy, France) analyzed electrocardiograms (ECGs). RESULTS Electrocardiograms were analyzed in 757 patients at base. line, 744 before-discharge, and 715 after 30 days. In both arms, mean PR interval and QRS duration increased from baseline to predischarge (PR: Myval Delta + 21 ms [P < 0.01] contemporary Delta + 15ms[P < 0.01] QRS: Myval Delta + 15 ms [P < 0.01] , contemporary Delta + 17 ms [P < 0.01] ) and to 30 days (PRMyval Delta + 7 [P < 0.01] contemporary Delta + 3 ms [P < 0.01] QRS: Myval Delta + 10 ms [P < 0.01] contemporary Delta + 9 ms [P = 0.07] ) Before discharge, left branch block (LBBB) was in 19% of the Myval and 24% of the contemporary group. At 30 days, the frequency of LBBB decreased to 12% in both arms. The occurrence of new PPMI at 30 days was 15% in the Myval and 17% in the contem- porary arm. In both arms, 90% of patients received PPMI before discharge, with no differences in time between both arms. The leading cause of PPMI was complete atrioventricular block (AVB) (Myval 79%, contemporary 69%), followed by second-degree AVB (both arms 9%) and LBBB (Myval 7%, contemporary 11%). Among clinical sites that included more than 20 cases in the trial, the rate of PPI ranged from 0% to 33%, reflecting a wide range in clinical practice. Analysis of predictors for PPMI is ongoing and will be presented at TCT. CONCLUSIONS In the randomized LANDMARK trial, post-THV im- plantation significant increases of PR and QRS duration were observed in both the Myval and the contemporary arms, which partially resolved at 30 days. The rates of PPMI were similar between the 2 arms, with complete AVB being the most frequent cause. A significant COM variation in PPMI rates was observed among study sites.