Mechanical thrombectomy for acute ischemic stroke

Abstract

The overall aim of this doctoral thesis was to study the outcome and safety of mechanical thrombectomy, which is an endovascular technique for treating moderate to severe acute ischemic stroke caused by a large cerebral artery occlusion. The technique has been developed over the last two decades. At the onset of this doctoral project, only a limited numbers of studies on the technique had been published, but the results were very promising.

This thesis is based on five peer-reviewed publications. In these studies, it was found that: • patients with basilar artery occlusions who were treated using mechanical thrombectomy (at Karolinska University Hospital between September 2005 – November 2010), had a significantly better functional outcome compared to patients in other studies, where intravenous thrombolysis or no reperfusion therapy was given (Study I); • mechanical thrombectomy was a safe and effective method for restoring blood flow in selected patients suffering from a moderate to severe acute ischemic stroke that was caused by a large artery occlusion (Study II). This was concluded from an examination of patients with anterior and posterior circulation strokes who were treated with mechanical thrombectomy at Karolinska University Hospital between September 2005 – December 2011; • neither prior treatment with intravenous thrombolysis, nor advanced age, was significantly associated with a risk of symptomatic intracranial hemorrhage (Study II); • functional outcome three months after mechanical thrombectomy was equally good for those over 80 years of age as for those between 50-64 and 65-79 years of age (Study III). This was concluded from an examination of the subgroup of patients from study II with anterior circulation stroke, selected according to practice at Karolinska University Hospital; • in patients with wake-up stroke, there was no indication of poorer outcome (Study III); • endovascular treatment combined with intravenous thrombolysis led to a higher ratio of patients with improved functional outcome compared to patients treated with intravenous thrombolysis alone, with an absolute risk reduction of 19% (Study IV). This was concluded from a meta-analysis of six randomized controlled trials; • the estimated rate of thrombectomy in Sweden in 2013 might have been more than five times higher than the actual rate, if patients had been selected according to our practice at the Karolinska University Hospital (a practice similar to the recently published updated treatment recommendations from both European and American organisations) (Study V). This was concluded by comparing treatment proportions at our institution by level of stroke severity with stroke data from the rest of Sweden, provided from Riksstroke (the Swedish national stroke registry).

In conclusion, it has been shown that mechanical thrombectomy is a safe treatment, which significantly improves the likelihood of functional outcome for patients with moderate to severe stroke. The findings indicate that a substantial increase in demand for this treatment option should be expected. The main challenge now is to fully implement the technique in clinical practice and to be able to offer it to all patients throughout Sweden, not just to those who live in the proximity of a university hospital.