Introduction: Residual mitral regurgitation (MR) is associated with worse outcomes after transcatheter edge to edge mitral valve repair (TEER) but is difficult to assess by echocardiography. Shear-stress induced by MR leads to altered Von Willebrand factor activity (vWF:Act), also reflected by increased closure time with adenosine diphosphate (CT-ADP), representing potential ways to screen for residual MR. CT-ADP can be assessed easily during TEER and is known to normalize swiftly after the correction of turbulent flow. Hypothesis: The improvement of CT-ADP is quick enough to allow real-time procedural guidance. Methods: We enrolled 39 patients undergoing TEER. MR severity was assessed by echocardiography during the procedure, 24-hours and 1-month post-TEER. CT-ADP was measured before TEER, 8 minutes after each clip deployment, 1 hour and 24 hours after the procedure. CT-ADP values were related with vWF:Act and MR severity at each time point. Results: Of 39 patients after TEER, 6 (15%) and 8 (21%) patients had residual MR ≥ moderate at 24-hours and 1-month respectively. There was no significant change in CT-ADP values during the procedure. The decrease of CT-ADP was however significant 1-hour post-TEER with stable values at 24-hours (last clip deployment: 136 [110-193]; 1 hour: 99 [82-131] and 24 hours: 95 [82-121] seconds, p<0.001). Concomitant increase in vWF:Act was observed after the procedure (baseline: 1.76 [1.29-2.05]; 1 hour: 1.84 [1.79-1.85] and 24 hours: 2.32 [1.84-2.5] IU/ml, p=0.002). Patients were stratified into 3 groups according to the residual MR grade at 1 month (≤ mild vs. moderate vs. >moderate). CT-ADP was not different among the groups (p=0.74). However, the difference in CT-ADP (1 month vs baseline values) was associated with MR improvement at the same time points (r=0.50; p=0.007). Conclusions: Although CT-ADP decreases after TEER and correlates with vWF:Act and MR improvement at 1 month, this decrease is first observed 1 hour after the procedure and does not seem to be quick enough to provide real-time monitoring of MR severity during TEER.