“Sonolysis is back” after safely reducing endarterectomy stroke risk in randomised trial

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David Školoudík presenting at ESOC 2023

Positive results from a clinical trial involving a novel therapeutic procedure known as sonolysis—deployed during a carotid endarterectomy (CEA)—were presented at the recent European Stroke Organisation Conference (ESOC; 24–26 May, Munich, Germany).

“The randomised clinical trial confirmed the results of pilot studies that sonolysis using diagnostic 2-MHz probe is safe and significantly reduces the risk of stroke, transient ischaemic attack [TIA], and silent brain infarctions detected using brain MRI [magnetic resonance imaging],” said David Školoudík (University of Ostrava, Ostrava, Czech Republic), principal investigator for SONOBIRDIE—the trial in question. “In clinical practice, this could mean not only an increase in the safety of CEA, but also an expansion of indications for this procedure.”

As an ESO press release details, CEA is a well-established approach in the treatment of carotid artery stenosis, but carries stroke risks both during and immediately after the procedure that are “not negligible”, meaning methods for reducing said risks are needed.

Transcranial Doppler (TCD), which uses ultrasound beams with a specific frequency, is a non-invasive procedure that has been shown to have some potential effect on accelerating spontaneous or induced reopening of otherwise occluded arteries. In the multicentre, randomised, double-blinded, sham-controlled SONOBIRDIE trial, this novel therapeutic approach—also referred to as sonolysis—was evaluated for safety and effectiveness in reducing risks of stroke, mini-stroke or any infarction detected on brain imaging during CEA.

Patients from 16 European centres were recruited between 2015 and 2022. All of these patients had severe internal carotid artery stenosis (≥70%) with a clinical indication for CEA and were aged 40–85 years. They were randomised either to sonolysis or to a sham procedure. Neurological exams and MRI were performed both before and after CEA to detect any stroke, TIA or death within 30 days. Overall, the study recruited 1,004 patients with a mean age of 68 years, 31% of whom were women.

According to Školoudík, members of the SONOBIRDIE data and safety monitoring board “unanimously recommended” stopping the trial early due to “clear evidence” of effectiveness in November 2020—at which point 507 patients had been randomised to the sonolysis group and 497 had been randomised to sham treatment.

As per interim analyses, the investigators found that sonolysis during CEA was associated with a “significant reduction” in risks of stroke, TIA or death at 30 days, with rates of this composite primary endpoint being 2.2% in the sonolysis group versus 7.6% in the sham treatment group. The same trend was seen for both symptomatic strokes (1.8% vs 7.5%) and new ischaemic lesions on MRI (8.6% vs 17.4%), Školoudík also detailed.

Multivariate analyses presented by Školoudík revealed that female gender appeared to be the only baseline characteristic associated with an increased risk of a negative outcome with sonolysis, while atrial fibrillation and anticoagulation were not linked to a significant difference between the two groups (sonolysis and sham treatment).

The concluding finding of SONOBIRDIE—the fact that periprocedural stroke and TIA risks were safely and effectively reduced in the trial using a diagnostic 2-MHz probe—led ESOC session moderator Carlos Molina (Vall d’Hebron Hospital, Barcelona, Spain) to remark that “sonolysis is back”.

The results drew similarly positive comments on social media, with Ashkan Shoamanesh (McMaster University, Hamilton, Canada) quipping: “sonolysis re-emerges from the ashes with the SONOBIRDIE trial meeting its primary outcome […]”. On Twitter, Zoi Netou-Kandylidou (Accident Hospital Berlin, Berlin, Germany) echoed Molina’s sentiment that ‘sonolysis is back’, adding: “fans of ultrasound, rejoice”.


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