PVA embolization

Major disadvantages proximal occlusion due to cluttering of particles may leave major collaterals and distal circulation patent. Late recanalization after PVA embolization is described but is not a matter of concern in acute GIH. 

Tadavarthy et al. reported the first use of PVA as an embolic agent in patients with cervical carcinoma, hemangiosarcoma of the liver, hemangioendothelioma of the neck and forehead, and an arte-... 

Several studies have described the histologic effects of PVA particles on embolized blood vessels. Initially, PVA particles do not occupy the entire lumen of the embolized vessel [25,26]. Instead, they... 

When using a microcatheter, care must be taken to avoid plugging the lumen with embolic agent, particularly with PVA or resin microspheres, by increasing the dilution of the particles. Embolization is usually performed using 3-ml syringes to achieve adequate pressure. If the catheter becomes completely obstructed, an attempt to pass a wire through the catheter to clear it may be made but such an obstruction usually necessitates removal of the microcatheter and its replacement. 

Particulate embolization is an option when contrast extravasates and the bleeding branch is beyond the reach of superselective catheterization (Fig. 5.7). Non-calibrated polyvinyl alcohol particles (PVA) in sizes of 150-250 [i to 250-350 p or even larger should be used. The amount of particles should be kept as low as possible to avoid diffuse distal embolization. After each injection of 0.1-0.2 ml (up to a maximum of 1 ml) of a dilution of PVA, control arteriography should verify that the bleeding point has been... 

Polyvinyl alcohol (PVA) particles have been used in a number of series [6,10,17-20). The particles need to be suspended in iodinated contrast since PVA is not intrinsically radio-opaque otherwise it is not possible to fluoroscopically monitor the embolization. Because the PVA is flow directed, delivery of this embolic agent is less precise than with coils and more subject to local hemodynamics. If the catheter is obturating the feeding artery, the particles will not flow away as readily. Also as the vessel starts to become ocduded by the PVA, the resistance to flow increases and hence the potential for reflux to nontarget segments of bowel will increase. 

Probably the more common embolic agent used for LGI embolization is the microcoil. Both microcoils and PVA have been used successfully in reports of LGI embolization and while there have not been any trials to determine if one embolic agent is superior microcoils do have several advantages over... 

For this reason, when an embolotherapy is planned we recommend immediate cessation of prostaglandin Ej agonist infusion. In case of arterial spasm at the ostium of the uterine artery, the use of a coaxial system with a microcatheter is then required. It is possible to successfully catheterize the distal part of the uterine artery in most cases. In these circumstances, the preferred embolic agent is the one that can be easily delivered through a microcatheter, such as PVA (Polyvinyl alcohol) or Embospheres. We prefer to use particles with larger diameters, such as Embospheres 700-900 mg. Even if these particles are used for the above-mentioned reasons, additional Gelfoam embolization of internal iliac arteries is performed because of the extensive collateral pathways of the female pelvis. 

A newer embolic which is a tris-acryl collagen-coated microsphere (Embospheres, Biosphere Medical, Rockland, MA) was the first embolic approved by the FDA specifically for fibroid embolization. These particles are hydrophilic and nonabsorbable. They have a very smooth surface, and are softer and more deformable than PVA. They are easily administered through a microcatheter since they have a reduced tendency for clumping and aggregation. 

The angiographic endpoint of uterine artery embolization with non-spherical PVA or Gelfoam is usually until there is stasis or near stasis in the artery [35,45-49]. 

Although there are theoretical advantages to the use of Embospheres, clinical studies have not shown an advantage over PVA particles [27]. The volume decrease ofthe fibroids, and the uterine volume reduction is similar between Embospheres and PVA [54]. The volume of microspheres required for an embolization is larger than the volume of PVA required to complete an embolization [27]. In both retrospective and prospective study there does not seem to be a difference in post procedure pain or the use of narcotic use between PVA and microspheres [27,55]. 

If large ovarian arteries are found, they maybe embolized with relatively large embolic particles, PVA 500-700 pm or spherical embolic particles 700-900 pm (Fig. 10.3.9a,b). Alternatively many... 

In the short-term, UFE using gelatin sponge pledgets alone seems to show comparable results as those obtained with PVA particles [22]. Katsumori reported improvement in menorrhagia and in bulk-related symptoms in 98% and 97% of cases respectively at 4 months after embolization [22]. 

Fig. 10.4.5. Gross specimen ofhysterectomy obtained 3 months after embolization in a 34-year-old woman with a large fundal fibroid (11cm in diameter) associated with menorrhagia. Embolization was performed using small non-spherical PVA particles. A large infarcted fibroid (F) is seen in the uterine cavity and associated fundal perforation is seen (arrow)...

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