Impact of simulated MitraClip on forward flow obstruction in the setting of mitral leaflet tethering: An in vitro investigation.

Objectives We aimed to evaluate diastolic leaflet tethering as a factor that may cause mitral stenosis (MS) after simulated MitraClip implantation, using an in vitro left heart simulator. BackgroundMethodsLeaflet tethering commonly seen in functional mitral regurgitation may be a significant factor affecting the severity of MS after MitraClip implantation. A left heart simulator with excised ovine mitral valves (N=6), and custom edge-to-edge clip devices (GTclip) was used to mimic implantation of MitraClip in a variety of positions. Anterior mitral leaflet (AML) tethering severity was varied for each case (leaflet excursion of 75 degrees, 60 degrees, and 45 degrees, consistent with mild, moderate and severe tethering), and the baseline mitral annular area (MAA) was varied across samples (3.6-4.8 cm(2)). The resulting mitral valve area (MVA), and peak/mean mitral valve gradient (MVG) were measured in each case. ResultsConclusionsAML tethering severity was a highly significant factor increasing MVG and decreasing MVA (P<0.001). When GTclip placement was simulated with severe AML tethering, mean MVG >5 mmHg resulted more frequently than with GTclip placement alone (46% vs. 4%, respectively). However, severe AML tethering alone significantly reduced baseline MVA to 3.60.2 cm(2), and increased baseline MVG to 3.0 +/- 0.4 mmHg. At MAA above 4.7 cm(2), severe AML tethering did not cause moderate MS, even with placement of two GTclips (95% confidence). Our results show that diastolic AML tethering may predispose to MS after clip placement, however, MS was not observed when baseline MVA was above 4.0 cm(2). Severity of AML tethering may be an important criterion in selecting patients for edge-to-edge repair.