Non-target embolization

The complications of embolotherapy are well described, but vary in their manifestations depending on the affected end-organ [85, 86]. By nature, success depends on complete abolishment of vascular supply, be it normal or abnormal vasculature. This can often be accomplished but not without a risk of compromise to adjacent normal tissue. Moreover, aggressive pursuit of difficult vascular territories poses a risk for non-target embolization. 

A spectrum of end-organ ischemic complications can occur with embolotherapy. Bowel infarction can complicate splanchnic embolization targeting bleeding or could result from inadvertent non-target embolization from an upstream source [88]. Gallbladder infarction or bile duct necrosis can complicate hepatic artery embolization or che-moembolization [89, 90]. Splenic abscess and overwhelming sepsis can occurs following splenic embolization [91]. Skin necrosis and nerve injury have been reported as a result of ethanol embolization of vascular malformations [53, 54]. Buttock muscular necrosis, buttock claudication and sexual dysfunction can occur as a result of internal iliac branch embolization, especially when distal or bilateral [92-95]. 

Finally, the injection technique of embolic particles is of paramount importance. Flow-directed injection of the particles respects the physiology of the circulation. Forceful injection can result not only in vessels damage or reflux but also in some situation, may provoke the opening of the normal vascular anastomosis with subsequent non-target embolization. 

Beware of causes of reflux of embolic material which can cause non-target embolization ... 

The follow-up should be focused on the possible complications and clinical outcome (Table 4.3). In the acute and immediate post-procedural phase, special attention should be directed to the early detection of sequelae of non-target embolization, which can often result in major complications. It is a good practice to routinely conduct a telephone interview with the patient no later than a week after the procedure. Modern interventionists are clinical providers and an interventional clinic followup at an appropriate period of time following a major embolization procedure is not an option but a required minimal standard of practice. 

These are very rare. Clearly all the complications relating to arterial catheterization at any site and for whatever reason can occur. Non-target embolization should not happen in the experienced hands of a well trained operator. It is said that fungal abscesses are commoner after hepatic arterial embolization [3] but there is no real evidence for this and most patients have had surgery or a penetrating injury prior to the embolization. Liver infarction as described above is uncommon but a rise in liver enzymes is often observed [3]. 

Rare complications as have been reported in literature are aortic and bronchial necrosis [58], bronchial stenosis [59], unilateral diaphragmatic paralysis [60], pulmonary infarction (especially in patients who have suffered pulmonary artery embolism), left main bronchial-esophageal fistula [61], and non-target embolization (colon, coronary and cerebral circulation) [62]. Especially the newer spherical embolic materials (tris-acryl gelatin) can traverse from the bronchial into the pulmonary circulation, and then through unoccluded pulmonary arteriovenous malformations into the systemic circulation [41]. 

The more peripheral the embolization is to the tumor, the less the opportunity for collateral circulation and the greater likelihood of tumor necrosis. While tumor necrosis is a desired effect, necrosis of adjacent non-targeted tissue is not. Microcatheter coaxial systems allow subselective or superselective embolizations to access tumor vessels and avoid non-targeted embolization. Peripheral embolization produces small vessel occlusion without sacrificing the main arteries, allowing future re-embolization when necessary. 

Fig. 4.13. a Marked parasitic supply to the tumor from the cystic artery (arrow), b In order to diminish the probability of non-target deposition of microspheres within the gallbladder, coil embolization of the parasitic branch is carried out. c The subsequent angiogram shows flow redistribution with complete opacification of the tumor bed which has now been disconnected from the cystic artery... 

Choice of embolic material/method is paramount and must be based on the target vascular territory and the desired effect. Ability to reach distal vascular beds. For example, emergent non-selective embolization of a large vascular territory is best accomplished with a potentially temporary occlusive agent such as Gelfoam. 

Transcatheter embolization has the potential to further reduce mortality in acute non-variceal upper GIH, provided we continue our efforts to optimize the occlusive technique and enhance the haemostatic effect. Furthermore, increasing angiographic sensitivity, which in our opinion depends much on the alertness of the involved endoscopist, will reduce the need for non-targeted blind embolization. Whether transcatheter techniques can replace surgical salvage in upper GIH remains to be established by prospective randomized studies. 

A complication rate of 8.7% was reported in the literature [56-59]. This includes contrast-induced, puncture and embolization related complications. The reported complications related to the embolization include foot ischemia, bladder necrosis, rectal wall necrosis, nerve injury and uterine necrosis. These complications are caused by non-targeted vessel embolization. 

Another case features a transient necrotic-appearing area on the right labium minus 5 days post UAE in a 38-year-old woman [110]. This was thought to be due to non-target labial embolization during UAE, perhaps of the internal pudendal artery. Spontaneous resolution occurred during the ensuing 4 weeks. 

To achieve safe embolization, it is important to use accurately sized coils. Selection of a coil too small for the intended artery leads to its distal migration and occlusion of the non-target distal branches. Conversely, proximal dislodgement can occur in a short target area during the delivery... 

Complications The complications that arise from embolization can be catheter-related (pseudoaneurysm, A-V fistula, dissection, thrombosis, perforation) or related to the occlusion effects on the tumor, parent organ, or non-targeted arterial supply (pain,ischemia/infarction, abscess) (Fig. 9.2). In a series reported by Hemingway and Allison (1988), compKcations from embolization represented a 10-year experience with 284 patients undergoing 410 emboKzations. Minor complications occurred in 16%, serious complications in 6.6%, and death in 2%. The post-emboKzation syndrome (fever, elevated white blood cell count, and discomfort) was encountered after 42.7% of the procedures. The underlying abnormality and location usually determined the nature and risk of the compKcation. 

Several lipoplex systems have shown appreciable in vitro transfection activity. Recently, they have been optimized to achieve effective targeting to specific cells as well as the smooth release of the entrapped DNA into the cytoplasm. However, the systems still have unsolved problems, involving stability, non-specific uptake by RES, and cytotoxicity [71]. After an intravenous injection of the lipoplexes, aggregation is immediately induced, then eventually the large aggregates (> 400 nm) are trapped in the lung capillaries and cause an embolism. Thus, the lipoplex systems are still problematic, particularly when used in systemic routes. 

It is our goal to perfect our technique in order to get more consistent results, reduce complications, and establish uterine fibroid embolization for a durable time period. Large calibrated microspheres are equally effective to smaller non-calibrated particles to target the peri-fibroid arterial plexus. Calibrated microspheres are so easy to deliver through microcatheters that one may predict the progressive replacement of non-spherical particles in the near future. MRI has become the reference imaging tool before and after embolization. The use of contrast-enhanced studies allows early detection... 

Comparative studies In the RE-LY study 18113 patients with non-valvular atrial fibrillation were randomized to dose-adjusted warfarin targeting an INR of 2.0-3.0 or dabigatran 110 or 150 mg bd [39 ]. The primary outcome was the incidence of stroke or systemic embolism, while the primary safety end-point was the frequency of major bleeding. Compared with warfarin, dabigatran 150 mg bd reduced the incidence of the primary outcome (1.7% per year with warfarin versus 1.1% per year with dabigatran 150 mg bd RR = 0.66 95% CI=0.53, 0.82) and had a similar effect on major bleeding. Patients... 

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