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).