Ultrasound used during surgery to unblock arteries is a safe and effective method for reducing stroke risk. This technique could enhance care for patients with carotid disease.
A study published in The BMJ finds that it could also significantly reduce the risk of death.
The technique – sonolysis – applies continuous ultrasound directly to the artery to help break up blood clots during carotid endarterectomy. This procedure removes fatty deposits from the carotid arteries, which supply blood to the brain, face and neck.
Pilot studies have suggested a potential positive effect of sonolysis on stroke risk during this type of surgery, prompting researchers to evaluate this in a randomised controlled trial.
The findings are based on 1,004 patients (average age 68; 31% female) scheduled for carotid endarterectomy across 16 centres in three European countries (Czech Republic, Slovakia, and Austria) from 20 August 2015 to 14 October 2020.
A total of 507 patients were randomly assigned to the sonolysis group and 497 to the control group (sham sonolysis). All patients underwent carotid endarterectomy within nine days of randomisation.
The primary measure of interest was a combination of ischaemic stroke, transient ischaemic attack (TIA or ‘mini-stroke’), or death within 30 days of surgery, confirmed by a stroke neurologist.
Potential influencing factors – such as age, sex, conditions such as diabetes and high blood pressure, medication use and smoking history – were also taken into account.
Eleven (2.2%) of patients in the sonolysis group experienced ischaemic stroke, transient ischaemic stroke or death within 30 days of surgery compared with 38 patients (7.6%) in the control group – a statistically significant risk difference of 5.5%.
A total of 460 patients also received a brain scan before and one day after surgery: 236 in the sonolysis group and 224 in the control group. New brain lesions were detected in 20 (8.5%) patients in the sonolysis group and 39 (17.4%) patients in the control group – a statistically significant risk difference of 8.9%.
Sonolysis proved to be safe, with 94.4% of patients in the sonolysis group being free from serious adverse events 30 days after the procedure.
However, the rates of death within 30 days and over the course of one year did not differ significantly between the groups.
The precise mechanism by which sonolysis helps prevent strokes remains unclear. The authors propose that ultrasound waves can disintegrate blood clots and accelerate fibrinolysis.
They acknowledge that the sonographer could not be blinded, as only standard ultrasound machines were used. However, they point out that patients and all other health professionals involved in the trial were unaware of the group assignments.
Consequently, they conclude that sonolysis ‘has the potential to make carotid endarterectomy safer, providing greater benefits for patients with carotid stenosis compared to the best medical treatment, especially in those with asymptomatic carotid stenosis’.
This trial has several strengths; however, a US vascular surgeon in a linked editorial notes that there are some questions regarding the study design and results that should be considered before the widespread adoption of this technique.
However, he adds that resolving these concerns and conducting a cost-effectiveness calculation ‘can then inform whether this exciting new application of an established technology can enhance care for patients undergoing carotid endarterectomy’
