SIR 2022: Treating placenta accreta spectrum with multivessel pelvic embolization

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The findings of a collaborative research project at the University of California San Diego, San Diego, USA were presented in an abstract titled ‘Multivessel pelvic embolization during caesarean hysterectomy for placenta accreta spectrum: A single-centre experience and comparison to internal iliac artery balloon occlusion’ at the Society of Interventional Radiology (SIR) 2022 Annual Meeting (11–16 June, Boston, USA).

This collaboration among interventional radiology, obstetrics and gynaecology, and maternal foetal medicine teams aimed to compare how intraoperative pelvic embolization performed to reduce blood loss during surgical management of placenta accreta spectrum (PAS) versus internal iliac artery balloon occlusion (IIABO). The abstract’s lead author, Christine Boone, explained to Interventional News ahead of the presentation her surprise at the extent of blood loss reduction with embolization compared IIABO, alongside some of the other aspects of her research.

Regarding the study’s results, Boone first outlined her prediction that blood loss would be “similar or better” among the embolization group. “But what surprised me was by how much [embolization improved outcomes],” Boone went on to acknowledge. In the IIABO group, she noted, median blood loss was 2.5 litres, where any amount over one litre in a caesarean section delivery is considered a haemorrhage. “It was a lot more before [occlusion], and people had to get blood transfusions,” Boone said, contextualising the benefit that IIABO intervention brings. Yet, the median blood loss, she then noted, with embolization, was only 675ml “which is not even considered a haemorrhage by the criteria for caesarean [delivery].” In this group, no patients needed transfusions, which was not the case for the occlusion group. Boone labelled this “a really striking difference,” accounting for her surprise at her study’s findings. Of note, the comparative procedure times for IIABO and embolization, which were an average of 35 and 64 minutes, respectively, Boone admitted that the duration of the procedures is an important consideration. While the longer duration of the embolization procedures did not present issues in the context of the study, it may in some cases.

Christine Boone

The abstract was also recognised as ‘exceptional’ among those presented at the meeting. Additionally, Boone received the SIR Foundation Resident Research Award during the meeting’s award ceremony plenary session on Monday 13 June.

Boone began by relaying to Interventional News how she was inspired to study the applications of interventional radiology (IR) in women’s health after “[repeatedly] hearing about how maternal mortality was increasing in the USA” as she was finishing medical school. “I thought this was so strange,” she admitted, given “how we pay so much for healthcare in this country.”

Expanding on what drew her into women’s health and IR, she conveyed her passion for being “able to intervene, especially in postpartum haemorrhage situations” and that “that was the thing that would often kill women in childbirth.” Boone went on to underline how haemorrhage management can be achieved in “as little as 15 minutes,” and that this is one of the reasons why she sees her area of research as a “really exciting opportunity to help.”

Learning more about placenta accreta spectrum disorders, Boone highlighted as “fascinating”, not just from a treatment point of view, but also from a scientific standpoint. “The more I read about it, the more I learned that it was almost like a malignancy […] it does not respect boundaries […] and behaves like a cancer.” Spreading greater awareness about the disease is, therefore, something about which Boone feels strongly.

Quizzed on the two treatment options compared in her research project, Boone first conveyed how there is, currently, no standard of care regarding PAS treatment. Different clinicians may choose different approaches, including hysterectomy, as well as leaving the placenta in place to manage bleeding (the latter, however, brings with it risk of infection). IR provides a further swathe of treatment options, such as embolization and balloon occlusion, Boone detailed.

According to Boone, this application balloon occlusion “came earlier”, but that it is not necessarily used more often than embolization nowadays, as there isn’t data available on this. Nevertheless, the fact remains that there is more research on the former type of treatment. Aortic balloons are used in trauma situations, and so are widely seen as an effective method for stopping blood flow, hence the recourse to them in a PAS treatment scenario, Boone proceeded. She then detailed how aortic balloons have, in fact, been used for PAS cases during surgery, but that this threatens limbs and other organs by stopping blood flow to everywhere below where the balloon is inflated. Consequently, “the benefit of the [IIABO] is that it is more selective […]—the internal iliac artery [supplies] blood to everything in the pelvis, but the legs are excluded”.

Despite this advantage of IIABO, Boone then shared her thoughts on why embolization may work better still: “The placenta in PAS does not respect [anatomic] boundaries, including its vascular supply and so it can pull blood from the abdominal wall [for example].” This may mean that, in certain cases, the IIABO’s role is insufficient, as it is not stopping blood flow to additional vessels in question. Embolization is favourable in these cases, Boone outlined, expanding on this point with the following explanation: “[with embolization], we are looking for collaterals […] we can adapt the therapy to the unique situation of the patient and where the blood is coming from.”

The discussion then turned to the specific particles one can use for embolization to treat PAS. Boone began by conceding that no study to date has compared particle types for this indication. There can be different approaches to embolization and the type of particle is an important consideration in this strategy. Studies to determine optimal embolization strategies and embolic type would be a significant next step.  Another “good future direction” for research would be subgroup analysis, as the study is ongoing. Boone explained, however, for now, the number of patients is too low for this to be possible. “There is definitely something to be said for gravidity [and there also could be] for the number of caesarean sections a patient has had,” Boone stated.

In conclusion, Boone told Interventional News how she sees these results as “huge”, and she is excited to see the impact they might have for PAS care. She also took the opportunity to give insight into her other area of research. Currently used in the treatment planning of pelvic venous disease at the University of California San Diego, Boone shared her interest in taking 4D flow magnetic resonance imaging (MRI) into the area of PAS, to see if it could aid in identifying where the placenta is drawing blood from in each specific patient’s case, ahead of the procedure, which could make treatment faster.

 


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