Published online before print November 17, 2011, doi: 10.3174/ajnr.A2900
AJNR 2011 32: E211

M. Bergui^a
aNeuroradiology
University of Turin
Turin, Italy

In the August issue of the American Journal of Neuroradiology, Al-Ali et al¹ compared the results of percutaneous angioplasty (PTA), balloon-mounted stent (BMS), and the Wingspan system (Boston Scientific, Natick, Massachusetts) in the treatment of intracranial stenoses.¹ Both short- and long-term results strongly favored PTA over BMS and Wingspan. The latter, in particular, compared unfavorably with the natural history of the disease in the first year after intervention. The choice of the intervention was not randomized.

In this setting, selection bias affects the results. I noticed that the Wingspan had a 28.8% risk of dissections, against 19.1% for PTA; this is unexpected because angioplasty, the most dangerous part of the procedure with respect to dissection, was performed as a first step in both procedures. In the “Discussion,” while explaining their actual policy of treatment, the authors said that the Wingspan is used only when dissection occurs. Does that mean that PTA was switched to the Wingspan if dissection occurred? If so, because dissection represents a relevant risk for stroke, the results may be deeply biased. The “intention-to-treat” analysis that was used to assess the success rate remains unbiased by treatment switches because single results are attributed to the treatment that was “intended to” and not “effectively” used. This type of analysis would be indispensable to strengthen the results of this very interesting article.

References

1. Al-Ali F, Cree T, Hall S, et al. Predictors of unfavorable outcome in intracranial angioplasty and stenting in a single-center comparison: results from the Borgess Medical Center-Intracranial Revascularization Registry. AJNR Am J Neuroradiol 2011;32:1221–26. Epub 2011 May 5 » Abstract/FREE Full Text

Reply

Published online before print November 17, 2011, doi: 10.3174/ajnr.A2926
AJNR 2011 32: E212

F. Al-Ali^a
aNeurosurgery of Kalamazoo
Neurointerventional Surgery and Diagnostic Services
Borgess Medical Center
Kalamazoo, Michigan

We appreciate Dr Bergui’s comments concerning our recent article in which we questioned the safety of intracranial stent placement. Neither the Wingspan system (WS) (Boston Scientific, Natick, Massachusetts) nor the balloon-mounted stent arm compared favorably with the natural history of the disease as shown by the Warfarin-Aspirin Symptomatic Intracranial Disease study.¹ The angioplasty arm, however, did.

Dr Bergui raised a few legitimate questions that we would like to address here. He first questioned the higher dissection rate in the WS arm because angioplasty is the more dangerous part of the procedure in terms of dissection. We think the explanation for this phenomenon is that less time was spent performing angioplasty (30 seconds on average) before placing the stent, which gives the operator a false sense of security. On the other hand, when angioplasty was performed alone, especially before the availability of a self-expandable stent, strict care was observed to avoid dissection because if faced with dissection, there was no sure way of protecting the vessel from occlusion, making the possibility of massive stroke very real. Therefore, angioplasty was performed with a very slow inflation technique (3–4 minutes were typical).

Concerning the second question, whether WS was used if significant dissection was encountered following angioplasty, we confirm that this was not the case. We stated clearly, in the “Vessel Treated” and “Device Used” sections of the article, that by the introduction of the WS in November 2005, angioplasty was entirely replaced by the WS and we did not perform a primary angioplasty after that time. We did observe our initial plan about the intended procedure, and all complications were assigned the initial procedure intended.

We are comfortable with our results, and the recent publication of the Stenting and Aggressive Medical Management for Preventing Recurrent stroke in Intracranial Stenosis (SAMMPRIS) study² vindicated our results and our early doubt of the SAMMPRIS study design and usefulness. It is disheartening to see that we needed to perform such an expensive study to prove something a lot of people in the field knew already.

References

1. Chimowitz MI, Lynn MJ, Howlett-Smith H, et al. for the Warfarin-Aspirin Symptomatic Intracranial Disease Trial Investigators. Comparison of warfarin and aspirin for symptomatic intracranial arterial stenosis. N. Engl J Med 2005;352:1305–16 » CrossRef » Medline
2. Chimowitz MI, Lynn MJ, Derdeyn CP, et al. for the SAMMPRIS Trial Investigators. Stenting versus aggressive medical therapy for intracranial arterial stenosis. N. Engl J Med 2011;365:993–1003 » CrossRef » Medline