Discussion
The first clinical trial for the HeartMate 3 was initiated in
2014.4, and it was approved by the Food and Drug
Administration(FDA) for the commercial use in 2017. It was reported that
the HeartMate 3 pump showed either comparable or more favorable outcomes
compared to the HeartMate 2 in terms of device-related complications
such as a remarkable reduction in stroke rates1.
However, there has been a device-related complication exclusive to the
HeartMate 3, which is spontaneous outflow graft twisting in a long-term
phase. Although the mechanism of late graft twist has not been clearly
understood, the helical heart motion, ventricular remodeling, and/or
metallic swivel joint configuration have been considered to lead to this
issue2,3. According to the report from MOMENTUM3
trial, the incidence of late outflow graft twisting was 1.6% and the
median duration from the index surgery was 544 days2.
In our case series, the incidence was 2.4%(2/84) and its median
duration from the index implantation was 495days. As for diagnostic
modality, it is generally recommended to obtain a CTA to detect the
outflow graft twisting. In our first case, a CTA revealed a narrowing of
the outflow graft, and the final diagnosis of twisting was confirmed
during surgery. Thrombus formation inside the outflow graft would be an
important differential diagnosis because it would need a different
surgical strategy to avoid embolic events. However, it is sometime
difficult to differentiate those diagnoses only with a CTA although it
is known that most of late outflow graft twisting occurred at a proximal
portion of the graft near the device connection2,3. In
our 2nd case, we performed an outflow graft
angiography and it was very helpful to confirm the outflow graft
twisting preoperatively. The graft angiography clearly showed a graft
twisting and the pressure measurement demonstrated significant pressure
gradient at the twisted point. An outflow graft angiography would be
recommended in patients with a suspicious outflow graft twisting.
In terms of surgical approaches, a full resternotomy is one of options.
However, it would require a full dissection of the heart and the device
to fix the problem, which might need a cardiopulmonary bypass. A left
thoracotomy could be another option. It will provide a reasonable access
to the device body, however it would suffer from a limited exposure to
access the main target; specifically the outflow graft which lies down
anterior/medial side of the chest. We utilized a subcostal approach
which allow us to access directly to the target area(i.e. the outflow
graft and the device connector) in a less invasive fashion, and we
successfully fixed the problems.
As a number of this issue being reported, outflow graft connector clips
to avoid a twisting waere released in October 15th,
2018 by Abbott(Abbott Park, IL). Eventually, integrated pump cover was
released on November 11th, 2019. Index implantations
for both our cases were before the clip was released. It is important to
note that we did not place a clip during the surgery due to anatomical
reasons. We believe that the connector would not rotate again due to
severe adhesion. However, this could be a trade-off in a subcostal
approach and we would need a close follow up for our patients.
In conclusion, we have experienced two cases of spontaneous outflow
graft twisting in patients supported with a HeartMate 3, and
successfully treated with a surgical repair using a subcostal approach.
Acknowledgements: none
Disclosures: Dr Jeevanandam is a scientific advisor of Abbott
The institutional review board of our institution approved this study
and waived the requirement for informed consent.
Author contributions;
Hidefumi Nishida; concept, drafting article
Valluvan Jeevanandam; Critical revision of article, Approval of article
Takeyoshi Ota; Critical revision of article, Approval of article