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