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\begin{document}

\title{Surgical Correction of Spontaneous Outflow Graft Twisting of HeartMate
III via a Subcostal Approach}



\author[1]{Hidefumi Nishida}%
\author[1]{Valluvan Jeevanandam}%
\author[1]{Takeyoshi Ota}%
\affil[1]{University of Chicago}%


\vspace{-1em}



  
  \date{May 04, 2024}


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\selectlanguage{english}
\begin{abstract}
We experienced two cases of successful surgical correction of HeartMate
3 outflow graft twisting through a subcostal approach. They were
diagnosed with computed tomography or pull back pressure measurement.
Technically, a subcostal approach allowed us to access directly to the
twisted outflow graft and the device connector in a less invasive
fashion without a re-sternotomy. Diagnostic modality and surgical tips
are presented.%
\end{abstract}%



\sloppy


\textbf{Introduction}

HeartMate 3 is a centrifugal-flow left ventricular assist device(LVAD)
and the most updated version of circulatory support device. It has been
reported that the device provides less incidences of device-related
complications compared to the previous version of
HeartMate\textsuperscript{1}. However, there are a number of reports of
late spontaneous outflow graft twisting events exclusively to HeartMate
3\textsuperscript{2,3}.

\textbf{Case}

Case 1; A 54 year-old female was admitted due to shortness of breath and
persistent LVAD low flow alarm. Her initial surgery(HeartMate 3
insertion with mitral and tricuspid valve repair) was 2 years and 6
months prior to this presentation. The LVAD pump flow was 1.4L/minute
with 5400 rpm on admission, which was significantly lower than the
baseline(i.e. 4.0L/minute with 5400 rpm). An echocardiography revealed
that the aortic valve was open with every beat with a dilated left
ventricle. While lactate dehydrogenase(LDH) level was slightly
elevated(256U/l), serum haptoglobin(145mg/dl) and indirect
bilirubin(0.2mg/dl) were within normal range. A computed tomography
angiography(CTA) showed significant outflow graft narrowing at the
vicinity of the LVAD pump(Figure 1A,1B).

Case 2; A 38 year-old male presented with shortness of breath, abdominal
distension, nausea and vomiting. He had had the initial HeartMate 3
implantation and mitral valve repair 1 year and 6 months before. His
pump flow was slightly lower than his baseline, specifically 4.0L/minute
with 6200 rpm on admission and 5.1L/minute with 6200 rpm as baseline. An
echocardiography demonstrated that the aortic valve was open with every
beat. Lab data showed that lactate dehydrogenase(LDH) level was
elevated(425U/l), serum haptoglobin was low(36 mg/dl) and indirect
bilirubin was elevated(3.1mg/dl). An outflow graft angiography was
performed, which showed an apparent outflow graft twisting at the
proximal portion of the outflow graft(Figure 1C) with a significant
pressure gradient about 100mmHg at the twisting by a pull back pressure
measurement(Figure 1D,1E).

Both cases were taken to the operating room with a diagnosis of outflow
graft twisting/kinking. A subcostal approach was utilized to access
directly to the proximal portion of the outflow graft. A reverse-J shape
incision was made in the subcostal area and the outflow graft was
exposed enough to access to the connection between the outflow graft and
the device body. A Rultract retractor (Rultract Inc., Ohio) was used to
lift the rib to obtain a reasonable exposure (Figure 2A). The bend
relief was identified, the plastic frames of the bend relief were
partially removed, and the bend relief was longitudinally opened to
exposed the outflow graft. It was found that the outflow graft was
twisted about 3-4 cm from the device connector (Figure 2B). While the
bend relief was stuck to the surrounding tissue, the bend relief was
detached from the connector using the HeartMate accessory instrument.
Then, the connector was rotated in a direction for untwisting the
outflow graft. A curved-up Rongeur forceps was helpful to rotate. In
both cases, it required to rotate in a counter clockwise fashion in 120
degree to fix the twisting(Figure 2C,2D). Hemodynamics and LVAD
parameters were immediately improved. We did not place an outflow graft
clip given the risks to injure the surrounding structures during a
dissection with a relatively limited exposure. The opening of the bend
relief was covered with a Gore-Tex soft tissue patch(WL Gore \& Assoc
Inc, Flagstaff, Ariz). After decent hemostasis, the incision was closed
in layers in the routine fashion. The postoperative course was
uneventful. No recurrent issue has been noted for 4 months of the follow
up period.

\textbf{Discussion}

The first clinical trial for the HeartMate 3 was initiated in
2014.\textsuperscript{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 rates\textsuperscript{1}.
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
issue\textsuperscript{2,3}. 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 days\textsuperscript{2}.
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 connection\textsuperscript{2,3}. In
our 2\textsuperscript{nd} 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 15\textsuperscript{th},
2018 by Abbott(Abbott Park, IL). Eventually, integrated pump cover was
released on November 11\textsuperscript{th}, 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



\textbf{References}

\begin{enumerate}
\tightlist
\item
  Mehra MR, Uriel N, Naka Y, et al. A Fully Magnetically Levitated Left
  Ventricular Assist Device - Final Report. N Engl J Med. 2019 Apr
  25;380(17):1618-1627
\item
  Mehra MR, Salerno C, Naka Y, et al. A tale of the twist in the outflow
  graft: An analysis from the MOMENTUM 3 trial. J Heart Lung Transplant.
  2018 Nov;37(11):1281-1284.
\item
  Potapov EV, Netuka I, Kaufmann F, Falk V, Mehra MR. Strategy for
  surgical correction and mitigation of outflow graft twist with a
  centrifugal-flow left ventricular assist system. J Heart Lung
  Transplant. 2018 May;37(5):670-673.
\item
  Schmitto JD, Hanke JS, Rojas SV, Avsar M, Haverich A. First
  implantation in man of a new magnetically levitated left ventricular
  assist device(HeartMate III). J Heart Lung Transplant.
  2015;34(6):858-860.
\end{enumerate}

Figure legends:

Figure 1A,1B:Computed tomography showed an outflow graft twist(white
arrow)

Figure 1C:The graft angiography showed a graft twisting(white arrow)

Figure 1D,1E:A pull back pressure measurement showed a significant
gradient before(white arrow) and after(white arrow head) the twisting

Figure 2A: Subcostal approach. A Rultruck retractor was useful to lift
the rib and expose the surgical field.

Figure 2B: Graft twisting.

Figure 2C:The graft is being untwisted with a curved-up Rongeur forceps.

Figure 2D:The graft was untwisted and fixed.\selectlanguage{english}
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