Hemodynamic effect of iatrogenic atrial septal defect after percutaneous mitral valve repair using the MitraClip device

Abstract

Aim: Percutaneous mitral valve repair (PMVR) using the MitraClip device has become a therapeutic alternative for high surgical risk patients with symptomatic mitral regurgitation. The procedure involves transseptal puncture and results in a new atrial septal defect (ASD) after withdrawal of the 22F MitraClip guiding catheter. The functional effect of the new atrial septal defect is not defined. Methods: In 28 patients with symptomatic mitral regurgitation undergoing PMVR using the MitraClip device, 3D TEE was used to measure by direct en-face imaging the area of the new atrial septal defect, to determine the resulting left-to-right atrial shunt volume and define the left atrial pressure reduction resulting from the new ASD. Analysis of the velocity time integral (VTI) across the septal defect after withdrawal of the guiding catheter allowed calculation of the shunt volume. Diastolic VTI analysis of the mitral flow was performed before and after withdrawal of the MitraClip guiding catheter to determine the change in inflow into the left ventricle. Direct left atrial pressure measurements were obtained before and after withdrawal of the MitraClip guiding catheter. Results: Mitral valve regurgitant volume by color Doppler 3D TEE was determined as the product of vena contracta areas defined by direct planimetry and velocity time integral using continuous-wave Doppler. Regurgitant volume was reduced from 86±31 mL preintervention to 43±22 mL postintervention. The new ASD had an effective area of 0.19 cm2, 44% of the area of the 22F guiding catheter. Considering the VTI across the septal defect of 72±25 cm/sec, the left-to-right atrial shunt volume was calculated to be 13±5 ml per heart beat. The diastolic forward flow across the mitral valve was reduced by 15±11 ml/ heart beat immediately after withdrawal of the MitraClip guiding catheter. Mean left atrial pressure was reduced from 17±8 mmHg with the guiding catheter still in the left atrium to 15±8 mmHg after withdrawal of the guiding catheter. Conclusion: The creation of a new ASD as consequence of the large diameter MitraClip guiding catheter results in volume and pressure relief of the left atrium. This contributes significantly to the hemodynamic changes implemented by the MitraClip procedure.