From the Journals

Challenges of validating cerebral protection for TAVI

Publish date: November 2, 2017

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Trial ‘might never occur’

Dr. Messé and Dr. Furie pointed out the difficulty of quantifying the incidence of stroke during TAVI. But the long-term impact of stroke is more important because TAVI, as opposed to surgical aortic valve replacement, is more likely to be performed in a younger, healthier population, John Bozinovski, MD, of the University of British Columbia in Victoria said in his invited commentary (J Thorac Cardiovasc Surg. 2017;154:484-5).

While Dr. Messé and Dr. Furie make a valid point that clinically significant stroke, as opposed to diagnostically apparent stroke, is an important outcome of trials of embolic protection in TAVI, the long-term impact of silent strokes identified only with neuroimaging is unknown, “As such, ‘clinically significant’ stroke carries a nebulous definition,” Dr. Bozinovski said.

Nonetheless, CEP devices may become standard “even without good evidence” to support their use, Dr. Bozinovski said, “or perhaps they will be used infrequently or not at all.” Their uptake by cardiac surgeons will depend on the supporting evidence and their treatment effect. “Not only is it difficult to design an effective device, it is possible that we may not know whether a device is effective or what is the size of that effect,” he said. As Dr. Messé and Dr. Furie point out, “Designing and successfully conducting the trial to do so might never occur.”

Dr. Bozinovski disclosed he was a paid consultant with Edwards Life Sciences.

FROM THE JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY

While using cerebral embolic protection during transcatheter aortic valve implantation (TAVI) seems appealing to reduce the risk of stroke, which has been reported to be higher than in open aortic valve replacement, the challenge of developing practical CEP devices and then designing appropriate trials may be insurmountable, according to a featured expert opinion in the Journal of Thoracic and Cardiovascular Surgery (2017;154;880-3).

Dr. Steven R. Messé

Steven R. Messé, MD, of the University of Pennsylvania, Philadelphia, and Karen L. Furie, MD, of Brown University, Providence, R.I., called CEP for TAVI a ‘‘no brainer’’ in theory, and noted that the data so far seem promising. “Nevertheless, there are significant challenges to overcome before embolic protection becomes routine in clinical practice,” Dr. Messé and Dr. Furie wrote. “Developing a practical and safe device and testing it in a trial adequately powered to detect differences in radiographic and clinically meaningful endpoints is not a trivial task.”

Dr. Messé and Dr. Furie reviewed completed trials of five different CEP devices in 630 patients, noting that the trials confirmed the difficulty of “designing a trial that can prove a clinical benefit.” They noted 30-day stroke rates ranged from 4% to 6.7%, although prospective, nonrandomized European registries reported rates of 3.4% to 4.1%, and a large U.S. registry reported a rate of 2.5%. These results suggest “that some neurologic complications are going undetected or underreported in routine clinical practice.”

That may be a function of the different methods the trials used to determine complications. “There are little data to define best practice, but direct comprehensive assessment by a neurologist is likely the most accurate and sensitive method for detecting clinical stroke,” they added.

Another important factor is the timing of the assessment. They pointed out that half of all 30-day stroke events in TAVI are detected within 2 days of the procedure, but mild or transient symptoms can be missed if the only evaluation occurs just before discharge. “Unfortunately, in most studies this is when the neurologic assessment is performed,” Dr. Messé and Dr. Furie wrote. They added that long-term effects of these strokes have not been well studied.

Dr. Karen L. Furie

What’s more, many TAVI patients have subclinical ischemic injury that only neuroimaging can detect. “Studies of MRI performed early after TAVI have demonstrated acute infarcts in 68% to 97% of patients,” the stated. While small and multiple, these microinfarcts may not be totally silent. “Additional studies to assess the long-term implications of clinically silent infarcts are clearly needed,” the coauthors said.

They also noted that a trial of stenting vs. endarterectomy for carotid stenosis raises caution about CEP devices (Lancet Neurol. 2010;9:353-62), as patients who had angioplasty and stenting and were treated with a CEP device had higher rates of acute infarct detected on MRI than those who did not have the CEP. Placing the CEP device through a severely stenosed and symptomatic carotid artery may have led to additional cerebral emboli.

“Placing a cerebral protection device in the aorta for a TAVI procedure also could be problematic in the presence of severe aortic arch disease or variant anatomy,” Dr. Messé and Dr. Furie commented. With two large trials of embolic protection in TAVI currently underway, the coauthors said, “the field eagerly awaits these results.”

Dr. Messé has received research support from GlaxoSmithKline and Direct Flow Medical. Both Dr. Messé and Dr. Furie have participated in the National Institutes of Health/National Heart, Lung, and Blood Institute/National Institute of Neurologic Disorders and Stroke–sponsored Cardiothoracic Surgery Network.

Challenges of validating cerebral protection for TAVI

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