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Letters to the Editor |
, and
Robert White, MD 
* Departments of Medical Imaging, St. Michael's Hospital, 30 Bond St, Toronto, ON, Canada M5B 1W8
Department of Medicine, St. Michael's Hospital, 30 Bond St, Toronto, ON, Canada M5B 1W8
Department of Diagnostic Imaging, Yale University School of Medicine, New Haven, Conn
e-mail: r.p.chan{at}rogers.com
Editor:
In the May 2006 issue of Radiology, Dr Remy-Jardin and colleagues (1) propose an unusual classification scheme for treatment outcomes following embolotherapy of pulmonary arteriovenous malformations (PAVMs). Of 64 PAVMs, 47% were successfully treated (>30% reduction in aneurysm size), while 28% of PAVMs showed less than 30% aneurysm size reduction, with a persistent feeding artery diameter of less than 3 mm, which was considered partially successful treatment. An overall success rate of 75% (47% plus 28%) is claimed.
Persistent perfusion of embolized PAVMs, regardless of residual feeding artery diameter, warrants repeat embolotherapy. The 3-mm size threshold for embolotherapy of untreated PAVMs does not necessarily apply to embolized PAVMs (2). Reperfused PAVMs may actually pose higher risk of paradoxical embolization owing to potential in situ thrombus resulting from diminished flow. Residual shunting is known to persist despite successful embolotherapy, which is the rationale for continued antibiotic prophylaxis to prevent brain abscess (3).
The authors' success rate is really only 47%, substantially lower than that in other series (2,4–7). The longer follow-up period may account for this; however, additional factors may be responsible. A substantial proportion of patients (40%) were lost to follow-up. The authors treated patients starting in 1982 by using steel coils and a 7-F catheter, although a detailed technical description is not provided. Were feeding arteries occluded proximally or close to the aneurysm? One wonders whether modern coaxial catheters, platinum coils, and digital angiography would improve outcome. Interestingly, the authors found no relation between coil number and treatment failure, which is contrary to our experience (8). Intuitively, it makes sense that sustained occlusion of a large PAVM requires multiple coils.
The authors fail to acknowledge important literature examining long-term results of PAVM embolotherapy. Mager and colleagues (7) followed 349 PAVMs over 62.2 months and reported 96% success. In a prospective study by Pollak et al (9) of 415 PAVMs, involution occurred in 97%. Most interesting in the latter study was the discovery of enlargement of small PAVMs to a size warranting embolization in 28 patients (18%), prompting reconsideration of the 3 mm treatment threshold.
We believe it is important that your readership not be left with the impression that the long-term effectiveness of embolotherapy for PAVMs is only fair. The proved durability of embolotherapy justifies its use as the treatment of choice. Continued follow-up to detect reperfused and enlarging PAVMs is crucial.
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  L B Smoot, D Obler, D B McElhinney, K Boardman, B-L Wu, V Lip, and M P Mullen Clinical features of pulmonary arterial hypertension in young people with an ALK1 mutation and hereditary haemorrhagic telangiectasia Arch. Dis. Child., July 1, 2009; 94(7): 506 - 511. [Abstract] [Full Text] [PDF]
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