CO2 Flush Offers Renewed Hope for TAVR Brain Protection

PARIS -- Researchers are giving cerebral embolic protection (CEP) another go, this time redirecting attention to the gaseous emboli that may cause harm in transcatheter aortic valve replacement (TAVR, or TAVI).

In a small first-in-man study, preemptive carbon dioxide flushing of TAVR valves did not alter the nearly 90% rate of acute lesions but the number of lesions per patient were 4.2, compared with 9.0 using saline flushing (P=0.032), according to Saud Khawaja, MBBS, of Imperial College Healthcare NHS Trust in London, reporting the INTERCEPTavi results here at the EuroPCR meeting.

"This study demonstrates the neuroprotective benefits of flushing TAVI valves using CO₂, by halving the number of cerebral infarcts as demonstrated on brain MRI. It is a novel study that provides an affordable, easy-to-use technique that can be applied in every catheter laboratory to reduce cerebral infarcts and thus improve the safety of TAVI procedures," Khawaja said of the single-center study.

He reported that procedural events were four new permanent pacemaker implants in the 30-person carbon dioxide arm and five in the saline arm of equal sample size. There were no cerebrovascular events, bleeds, vascular complications, nor any new atrial fibrillation, myocardial infarction, or in-hospital death.

To date, brain injury and stroke remain safety concerns of TAVR treatment for severe aortic stenosis.

The available Sentinel filter offers a physical barrier for solid debris that may otherwise reach the brain during the procedure, though physical evidence of trapped material hasn't translated into reduced new lesion volumes or fewer major adverse cardiac and cerebrovascular events. As a result, CEP has only a lukewarm reception in the real world.

"Reducing covert brain injury is important for long-term benefits as TAVI is increasingly used in a younger, lower-risk population," Khawaja stressed.

He told the audience that solid emboli may not be the only source of brain injury in TAVR.

The case for carbon dioxide flushing is supported by evidence of gaseous emboli causing cerebral injury in the literature on thoracic endovascular aortic repair, he said, adding that carbon dioxide is more soluble in blood than air and hence does not cause bubble formations that may cause covert brain injury -- and potentially future strokes.

Session panelist and TAVR inventor Alain Cribier, MD, of Hopital Charles Nicolle CHU Rouen in France, said he was "very much concerned" about preventing cerebral air embolism because of the possibility of long-term deficits. In contrast, he noted, bubbles in the coronary arteries in ST-segment elevation are "frightening" but can be eliminated in 5 minutes.

"The general feeling from neuroradiologists and radiologists is air is a bigger issue in the brain, with smaller vessels, and the occlusive effect of air bubbles going in is bigger than what we've seen [elsewhere]," Khawaja agreed.

Even so, it's never been shown that more embolic hits early on affect cognitive function, and that is the part of the puzzle that is hard to put together, commented session chair Darren Mylotte, MD, of University Hospitals Galway in Ireland.

INTERCEPTavi included 60 individuals (mean age 81) undergoing TAVR for severe aortic stenosis in 2021-2023. They were randomized and evenly split between carbon dioxide and saline flushing groups.

All underwent periprocedural continuous transcranial Doppler monitoring to differentiate hits from gaseous and solid emboli. Monitoring also showed that gaseous emboli were an issue for self-expanding and balloon-expandable valve designs alike.

Post-TAVR MRIs from day 1 to day 7 were available in 34 people for the present analysis. MRI results at 6 months were not available at the time of presentation, according to Khawaja.

He noted that a larger multicenter randomized trial is planned to further evaluate the effects of gas bubbling and carbon dioxide flushing for TAVR patients. He also suggested combining carbon dioxide flushing with physical CEP in a future study.

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