Preliminary experience with the micro vascular plug for the treatment of pulmonary arteriovenous malformation: case series of four patients

Hereditary Haemorrhagic Telangiectasia (HHT) is an autosomal dominant disease, frequently associated with arteriovenous malformations in the brain, lungs, gastrointestinal tract and liver (Faughnan et al., 2011). Pulmonary arteriovenous malformations (PAVMs) are anomalous communications between pulmonary arteries and veins and occur in 15–50% of people with HHT (Faughnan et al., 2011; Kjeldsen et al., 2000). They have one or more feeding arteries, an aneurismal sac and one or more draining veins; they can be simple (with one feeding artery) or complex (with more than one feeding artery).

PAVM can be associated with life-threatening complications, like transient ischemic attack (TIA), stroke, cerebral access, haemoptysis and haemothorax. Neurological complications occur via paradoxical embolisation (Cottin et al., 2004; Cartin-Ceba et al., 2013), while haemorrhagic pulmonary complications can occur due to rupture of PAVMs which is very rare, described in only a few cases (Kundu et al., 2010).

Screening for PAVMs has to be performed at the time of the initial evaluation for HHT using contrast echocardiography (CE) (Parra et al., 2010). CE is considered positive if there is detection of any bubbles in the left atrium; positive CE has to be followed by computed tomography (CT) of the thorax.

PAVMs are usually treated with embolisation to prevent complications (Iqbal et al., 2000, Moussouttas et al., 2000). Treatment aims to occlude the feeding artery as close as possible to the sac. Several devices have been used during the years (balloons, coils, microcoils, vascular plugs) with the generally good clinical outcome. However, recanalisation of embolized PAVM can occur in between 5 and 15% (Milic et al., 2005). Microvascular plug (MVP) is a new tool in the embolisation toolbox. It is a detachable nitinol skeleton plug, coated with polytetrafluoroethylene (PTFE) (Pellerin et al., 2014). There are potential advantages of using MVP, such as the ability to deploy through a microcatheter close to the PAVM sac with immediate occlusion. Further, the device can be retracted and replaced, less metal artefact compared to coils, possibility to prevent device migration and less probability to have recanalisation because of the PTFE coating (Boatta et al., 2017).

There are two sizes of MPVs: MPV-3Q used for arteries ≤3 mm or less in size, and MPV-5Q for arteries of 3–5 mm. Both microplugs are designed to be delivered through microcatheters, MPV-3Q is compatible with microcatheter of 2.4 Fr (0.021-in. inner lumen diameter), and MVP-5Q is compatible with 2.8 Fr (0.027-in. inner lumen diameter).

This preliminary report aims to describe the intraprocedural experience using MVP in the treatment of PAVM.

Three female and one male (mean age 32,5 years; range: 20–53) with PAVMs diagnosed on CE and CT have been embolized with MVPs.

This case series described an early experience with the new embolization material and showed high technical success and control during the embolization of four PAVMs. The main advantage of MVP is a possibility to deploy the plug through the microcatheter, and if the planning is accurate, only one MVP is needed to achieve complete occlusion. One important feature of the new device is that we need straight at least 12 mm long vessel to deploy the MVP precisely. In the case of vessel tortuosity and sharp take off of the branch vessels, the deployment can be more challenging. The best results are achieved when the embolization material is placed close as possible to PAVM sac and where the distance between the PAVM sac and embolization material is under 1 cm, especially in PAVM with small feeding artery as reported by (Stein et al., 2017). They found the higher rate of reperfusion of the PAVM in a case of the proximally placed embolization material. The present case with difficulties to deploy the microplug close to the PAVM sac in tortuous anatomy showed the potential limitation of this new device. The possible combinations of the microcoils and microplug can be a solution in such environment. However, the further study can confirm the value of such an approach.

The present reports in the literature have the same experience with the MVP (Boatta et al., 2017; Pellerin O et al., 2014; Conrad et al., 2015).

The possible migration of the device is mentioned as a complication because of the undersized diameter (Conrad et al., 2015). We did not have any distal migration as we followed instruction for use, where the vessels with a diameter of ≤3 mm should be embolized with MVP-Q3 and vessels with diameter 3–5 mm should be embolized with the MVP-5Q. However, in the present cases report CT control was not performed to evaluate device migration eventually. Other authors recommend coils placement additionally in a case of incomplete occlusion or in a case of plug migration (Trerotola S et al., 2010). The potential challenge with this technique using the MVP-5Q is that the microcatheter has to be exchanged to the 0.021-in. inner lumen to avoid jamming of the coils when pushing coils thought a 0,027-in. inner lumen microcatheter. It is very important to avoid or to reduce manipulation and exchange of the material to avoid thrombus formation eventually, and air embolism and pre-interventional planning are very important. The CT and angiography measurement before advancing the embolization material is usually sufficient to choose the appropriate material and avoid too much manipulation.

MVP embolization of PAVMs appears technically feasible, safe, and effective at early follow-up.

Further prospective studies on bigger populations are required to confirm long-term safety and efficacy of this promising new embolization material.