Chronic total carotid occlusion – a short history of treatment paradigms
Symptomatic chronic total occlusion of the carotid artery is associated with up to 5-6% annual risk of stroke despite medical therapy[1,3]. In 1973, Gomensoro, suggested that an occluded carotid can no longer cause distal embolization and should be treated as a benign entity. Nowadays, precisely 50 years after his recommendation, the standard treatment paradigm remains unchanged. Most centers around the world consider chronic occlusion as a medically benign condition in which ipsilateral stroke is prevented and should be managed by medical treatment. However, the risk of stroke in patients with grade to hypoperfusion can approach up to 30%, and strategies to address this problem are being sought worldwide with variable results.
By-pass surgery and COSS trial results – why it failed?
In 1980s, extracranial-intracranial (EC-IC) bypass was considered a solution for patients with ICA occlusion. After the EC-IC bypass was published in 1986 in the New England Journal of Medicine, and no benefit was found, the procedure began to be abandoned, and guidelines were rewritten. However, a subgroup of clinicians tried to identify a high-risk group of patients with total carotid occlusions that might benefit more from EC-IC bypass. They started developing SPECT perfusion imaging to identify patients with significant hypoperfusion, proving they are at a higher risk of stroke. Subsequently, they established a second EC-IC bypass trial in this subgroup of patients, which was called COSS trial and was published in 2011.
The COSS trial was also negative, and thus EC-IC bypass was nearly wholly abandoned for patients with chronic carotid occlusion and hypoperfusion. However, it teaches us some important points. The COSS trial reduced the incidence of recurrent events after successful surgery. Still, the trial was stopped early due to a high peri-procedural stroke and death rate that offset the long-term benefit of re-establishing adequate cerebral perfusion. If the peri-procedural strokes (12 out of 14 in the first 30 days arising during the first 48 hours) had been prevented, the trial would have been largely positive, with a rate of recurrent stroke of 9% in the surgical group and 22.7% in the non-surgical group. This data supports the hypothesis that reversing hypoperfusion ameliorates long-term prognosis.
Endovascular treatment, how to not repeat the tail of COSS trial?
Since clinicians are still faced with high recurrence rates and disabilities induced by chronic hypoperfusion, several groups have proposed different endovascular and hybrid surgery therapies[7,9]. Currently, available literature on the feasibility and safety of these approaches shows that successful recanalization is achieved in around 70% of cases, with a 5% morbidity and a 2% mortality rate. Moreover, early ischemic events in this metanalysis were encountered in 9% of patients, while hemorrhagic events in 5%. The peri-operative stroke rate was 15% in the COSS trial and 12% in the EC-IC bypass Trial. Reducing this acute complication rate seems imperative to ensure a potential long-term benefit of the procedure. In a recent publication with a small number of patients, it was shown that a modern approach to reconstruction could dramatically reduce the periprocedural stroke rate and obtain an overall permanent complication rate of 5%. However, the stability of the construct is still a problem as endovascular reconstruction is faced with up to 25% re-occlusion rate compared to more than 95% patency rate for bypass surgery[6,11].
In the following years, groups worldwide will develop endovascular recanalization strategies further. Hopefully, the industry will join the efforts and develop dedicated neuro-vascular materials for chronic occlusions. After the procedure is mature and reproducible enough – the time for testing and randomized trials will come. However, proving that Gomensoro is wrong and changing the treatment paradigm will not be an easy task!
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