Comment
We describe the unique presentation of a HM3 implantation within a systemic RV for D-TGA after Mustard palliation. While the atrial switch is now uncommonly performed as the principal operation, there are long-term survivors who inevitably develop systemic RV failure mostly due to an inability of the morphologic RV to sustain systemic pressures.1-3 As in LV failure, durable MCS should be a treatment strategy for refractory systemic RV failure.
HM3 implantation in the LV apex requires the inflow cannula to be inserted parallel to the interventricular septum and directed towards the atrioventricular valve. This can typically be performed without cardioplegic arrest and with reliance on TEE guidance. In our D-TGA scenario, there are several anatomic considerations that make apical implantation technically challenging. The morphologic RV is more tubular as opposed to the cone-shaped LV, and the less-developed RV apex, especially one that is hypertrophic or dilated, may not necessarily correspond to the apex of the heart. As such, insertion points can vary from the anterior to the diaphragmatic RV. The RV is also relatively more trabeculated, and the abundance of muscle bundles and papillary muscles can interfere with device placement and subsequent inflow drainage.
For these reasons, we advocate for cardioplegic arrest to decompress the heart and position the device under direct vision. Excision of trabeculations and moderator band have been reported4-6, but management of intersecting papillary muscle has not been described in this setting. Papillary muscle repositioning is a technique that is utilized for mitral7 or tricuspid8 valve repair. Suture redirection of the papillary head changes the vector of chordal attachments and of the atrioventricular valves while preserving the ventricular geometry. We use this method because the versatility of this technique allows the surgeon to reposition the papillary muscles in any direction to accommodate unpredictable VAD positioning. The one caveat is the possibility of functional tricuspid stenosis (TS), which can affect device inflow. It is critical to confirm minimal TS at the conclusion of the procedure. Tricuspid regurgitation will have limited clinical impact due to inflow suction limiting regurgitant volume.
The patient recovered well and was discharged on postoperative day 43. Positioning of the device on chest roentgenogram can be compared to that of “normal” left ventricular positioning (Figure 2).