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Implantation
To produce the most natural flow the PERIMOUNT Magna mitral bioprosthesis should be oriented so that there is no obstruction of the LVOT by the post or strut of the bioprosthesis. In addition, the sewing cuff of the PERIMOUNT Magna mitral bioprosthesis is asymmetric and should be oriented so that the anterior saddle shape is positioned over the native anterior leaflet aiding in a natural distribution of chordal force if leaflet preservation techniques are used. This also positions the cuff regions of highest flexibility over the posterior annulus which is often calcified maximizing annular-cuff coaptation. To achieve proper orientation of the bioprosthesis, the anterior region of the sewing cuff (marked by the space between the two post or strut markers - one double and one single) should be positioned over the LVOT. This results in the double marking positioned near the anterior commissure of the native annulus, the single marking near the posterior commissure of the native valve, and the non-marked commissure of the bioprosthesis near the 6 o’clock position. Sutures are placed in the sewing cuff of the bioprosthesis making sure to properly orient the bioprosthesis (Figure 1).
Once all annular sutures are placed in the sewing cuff, the bioprosthesis is lowered using the handle and gentle traction on the sutures to maintain tension and avoid suture entrapment or tangling (Figure 2). The bioprosthesis is carefully inserted into the annulus by bending the handle sufficiently to enable the insertion of the posterior strut first and then the anterior portion of the bioprosthesis. This may help reduce the risk of damage to the ventricle or annulus. Once seated, approximation of the annulus and sewing cuff is checked.
The handle is released from the holder without unscrewing it by cutting the single green thread attaching the adapter to the post near the handle (Figure 3). This provides additional access and visibility for tying. Do not cut the three green threads on the legs that attach the holder to the bioprosthesis until all sutures have been tied. Sutures are tied being careful to check that seating does not shift and the sutures are seated normally. When cutting the suture tails verify that the knots or any remaining suture does not touch the leaflet tissue of the bioprosthesis as these may interfere with its function or cause abrasion to the leaflet.
Once all suture knots are tied, the holder is removed. In some cases one or two remaining sutures can be tied only by removing the holder first. In these cases all the sutures adjacent to each of the three frame struts must be tied down before cutting the holder attachment threads as the protective tenting is no longer in place after the holder is removed. The holder is released by cutting the three green threads on the legs of the holder. This is achieved by placing a scissors or cutting blade in the cutting channels (Figure 4). The holder is removed from the bioprosthesis by securing the bioprosthesis to the annulus and grasping the holder with sterile gloved hands or protected forceps and pulling it away from the bioprosthesis (Figure 5).
After the holder is removed, the bioprosthesis should be visually inspected for any defects that may have occurred during the implantation procedure. The bioprosthesis leaflets should appear symmetric and normal (Figure 6). Often a surgical mirror can be used to view the ventricular side of the bioprosthesis to check for proper suture placement. Unlike a repaired native mitral valve or porcine bioprosthesis, a saline bulb pressure test will not generate adequate pressures to fully close the PERIMOUNT Magna mitral bioprosthesis. However, a general assessment can be made by instituting antegrade cardioplegia while applying a saline bulb test. The aortic valve is frequently incompetent which greatly aids in increasing the left ventricular filling and end-diastolic pressure. The saline bulb test on the PERIMOUNT Magna mitral bioprosthesis results in centrally directed flow across the central free space of the valve. All PERIMOUNT valves are inspected while under physiological pressures to make certain coaptation and flow is within specification. The PERIMOUNT Magna mitral bioprosthesis was designed to fully close only under physiological pressures and should be assessed with TEE once volume loading is balanced and cardiac output reaches normal.
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