medwireNews: Extracranial-intracranial (EC–IC) bypass surgery does not significantly improve outcomes or reduce deaths when combined with medical therapy for treatment of symptomatic patients with atherosclerotic occlusion of the internal carotid artery (ICA) or middle cerebral artery (MCA), indicate study results.
Liqun Jiao (Capital Medical University, Beijing, China) and Yuxiang Gu (Fudan University, Shanghai, China) and the CMOSS team explain that, in theory, EC–IC bypass surgery should be a “plausible treatment strategy” because anastomosis of the superficial temporal artery to the MCA should help restore blood flow.
To investigate, they assessed its performance in 324 stroke patients with occlusion of the ICA or MCA and hemodynamic insufficiency as measured using computed tomography perfusion. Criteria for hemodynamic insufficiency included a mean transit time (MTT) on the symptomatic side of longer than 4 seconds and a relative cerebral blood flow (rCBF) ratio on either side of less than 0.95.
The enrolled patients had a median age of 52.7 years and 79.3% were men. Most of the patients presented with stroke (55.6%) as opposed to transient ischemic attack (44.4%), and 57.4% were diagnosed with ICA occlusion and 42.6% with MCA occlusion.
The patients were randomly assigned to undergo EC–IC bypass surgery within 7 days in addition to receiving medical therapy comprising antiplatelet therapy and stroke risk factor control or medical therapy alone.
According to results published in JAMA, 8.6% of the evaluable 151 patients receiving EC–IC bypass surgery experienced the composite primary outcome of a stroke or death within 30 days or ipsilateral ischemic stroke beyond 30 days through 2 years. This was not significantly different to the 12.3% rate among the evaluable 155 patients receiving medical therapy only.
The researchers also observed no significant differences between the surgical and medical therapy groups for the trial’s secondary outcomes, which included measures such as the 2-year risk of any stroke or death (9.9 vs 15.3%), fatal stroke (2.0 vs 0.0%), and disabling stroke (4.1 vs 2.0%). They also found no significant differences between the treatments in subgroups of patients with an MTT longer than 6 seconds and an rCBF ratio of 0.8 or less.
The researchers note that the 12.3% rate of stroke or death in the medical therapy group was lower than their expectation of 28.0% and lower than results from previous studies, such as the Carotid Occlusion Surgery Study (COSS), adding that it was “nearly half of that reported in COSS a decade ago (21.0%).”
They suggest possible reasons for this difference may include improved efficacy of medical therapy, better control of atherosclerosis risk factors, or less severe hemodynamic insufficiency.
In an editorial related to the study, Seemant Chaturvedi and J Marc Simard, both from the University of Maryland School of Medicine in Baltimore, USA, commented that the case for EC–IC bypass surgery in patients with an ICA or MCA occlusion remains unsupported across three different randomized clinical trials.
“The changing aspect of the story is the improved results with medical therapy, consisting of antithrombotic therapy and treatment of risk factors such as dyslipidemia, hypertension, and diabetes,” they write.
But in terms of EC–IC bypass surgery, “[u]ntil a better understanding of the unique hemodynamic features of the brain is achieved, it will be difficult for neurosurgeons to continue offering this procedure to patients with ICA or MCA occlusion,” they add, saying that “intensive, multifaceted medical therapy remains the first-line treatment.”
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