Use of the Hourglass peripheral embolisation device: early experiences

The role of endovascular embolisation in both routine and emergent clinical practice continues to expand apace, along with an increase in the frequency and complexity of procedures being performed. Similarly, the array of embolic agents available to the interventional radiologist has expanded in recent years with the advent of novel vascular plug devices. The Amplatzer plug devices (St Jude Medical Inc., Saint Paul, MN, USA) are already well established [1–3]. Recent publications have shown promising results with the Microvascular Plug (Reverse Medical Corporation, Irvine, CA, USA) [4–6]. Endovascular coils are the current embolic agent of choice for occlusion of small-to-medium sized vessels; however, the variability in size and number of coils required to achieve target vessel occlusion is a major drawback of these agents. In contrast, vascular plugs allow target vessel occlusion with deployment of a single device thus shortening the procedure time, screening time and cost.

The Hourglass device is a novel vascular plug developed by EMBA Medical (Dublin, Ireland). The device was CE-marked for use in Europe in July 2015 and was approved for use by the Food and Drug Administration in August 2017. The device is an over-the-wire intravascular plug with a polytetrafluoroethylene (PTFE)-covered Nitinol frame which aims to provide immediate occlusion in small-to-medium sized vessels. To date, no published data exist on the use of this device. This paper describes a single-centre experience of embolisation for a variety of clinical indications using the Hourglass device in nine patients.

In 9/9 (100%) cases, the device was successfully deployed with immediate, angiographically proven occlusion of the target vessel. There was no observed foreshortening of the device and there were no instances of device migration. The average time taken to deploy the device was 5 min (range = 3–10 min).

Both operators rated the device as easy to use and deploy in 9/9 (100%) cases. Repositioning of the device was performed twice and was rated as easy in both cases. The device was easily visible under fluoroscopy in 9/9 (100%) cases. The trackability and stability of the delivery system was rated as good in 9/9 (100%) cases.

Patient outcomes were as follows: patient A died from complications related to the subsequent surgery; patient B underwent successful resection of the kidney one day after embolisation; patient C underwent follow-up non-contrast computed tomography (CT) of the abdomen, which showed the device in situ and necrosis of the tumour (Fig. 5a). Patient D had follow-up magnetic resonance imaging (MRI) one year later, which showed resolution of the perinephric haematoma (Fig. 6). Patient E had a follow-up CT which demonstrated the device in situ, marked cortical atrophy, and resolution of the hydronephrosis (Fig. 5b). All three patients who underwent varicocele embolisation reported symptomatic relief following the procedure. A follow-up CT angiogram one day post GDA embolisation confirmed satisfactory occlusion of the GDA with no evidence of extravasation.

This is the first published evaluation of the Hourglass device, a novel over-the-wire vascular plug delivered in the same manner as an endovascular stent – a familiar technique for interventional radiologists. The operators achieved a 100% technical success rate, scored the device as easy to use and reported a high level of satisfaction with both the device and the delivery system.

As described by Lubarsky et al. [7], the choice of embolic agent is based on the vessel size, the desired duration of embolisation and the need to maintain end organ viability. Vascular plugs are designed for permanent vessel occlusion and the use of a single device allows for rapid, accurate deployment compared with coils. A range of vascular plugs are available to suit the desired vessel characteristics; however, the operator must be aware of the differences in these devices in order to choose appropriately. The Hourglass device is a ‘one size fits all’ option, allowing deployment of a single device in vessels with diameters in the range of 3–8 mm. This has the potential to simplify procedures and reduce the range of vascular plugs required in stock.

We encountered no incidence of device migration or foreshortening in our study. While there were other embolic devices used for more distal embolisation in our patient cohort (i.e. endovascular coils and embospheres), the covered proximal end of the device was seen to result in immediate occlusion of the target vessel at the site of device deployment in all cases. The ability to inject contrast through the outer body side port allowed immediate confirmation of this target vessel occlusion. In theory, this could provide an advantage over other plugs whose interstices permit continued antegrade flow for a time following deployment; this results in a lower efficiency of occlusion and a variable and unpredictable time to occlusion [1, 3, 8]. Persistent patency has also been described as an issue with respect to other plugs, although this is less than with coil embolisation and usually in absence of angiographically demonstrable vessel occlusion at deployment [1–3]. In our study, immediate vascular occlusion was achieved and demonstrated in all cases.

The delivery system has an outer diameter of 1.67 mm allowing deployment through a 5-Fr catheter/sheath. The trackability of the delivery system was always rated as good, which is encouraging since this has been described as an issue with other vascular plugs [1]. The device was fully retracted and repositioned on two occasions without difficulty. We also noted a lack of device-related artefacts on subsequent CT and MRI, compared with the relevant artefact often encountered with endovascular coils.

One overall criticism of the device was reported by the operators. The length of the wire (300 cm) and the length of the delivery system (120 cm) provided with the device were felt to be excessive and inconvenient. However, a new 80-cm delivery system has since obtained a CE mark (March 2017), which may overcome some of these difficulties.

We acknowledge that this is a small case series at a single institution with a heterogeneous patient population and includes both arterial and venous interventions. Despite this, the authors believe that the outcomes of this feasibility study warrant larger-scale evaluation of the device.

In conclusion, the EMBA Hourglass device is a novel endovascular plug with several potential advantages over existing devices. The device was found to be easy to use, with a high level of operator satisfaction. It resulted into immediate, angiographically proven vascular occlusion at the time of the procedure. Its versatility allows the use of a single device in a range of vessel sizes and the delivery system allows for accurate deployment. No procedure-related complications were experienced in our cohort of patients. Larger studies will be required to fully evaluate the usefulness of this device and to confirm these early promising outcomes.