Imaging, Cognitive Testing Reveal Subtle Neurologic Damage Following Cardiac Procedures

More thorough neurologic assessment is needed for patients both before and after undergoing high-risk cardiovascular procedures, suggests new research from Cleveland Clinic investigators.

Brain perfusion: How robust is its protection?

Both transcatheter aortic valve replacement (TAVR) and aortic arch procedures place patients at particularly high risk for neurologic injury and stroke. While recent use of protective measures such as brain perfusion during aortic arch replacement has reduced this risk, use of brain MRI and neurocognitive testing reveals subclinical damage.

Those assessments aren’t traditionally used in research or clinical practice involving high-risk cardiovascular procedures, but the new study’s lead author, Lars G. Svensson, MD, PhD, believes they should be.

“Excellent results can be achieved with current techniques, but physicians need to be aware that there may be subclinical events happening that may have long-term consequences as far as neurocognitive function and dementia risk,” says Dr. Svensson, Chairman of Cleveland Clinic’s Sydell and Arnold Miller Family Heart & Vascular Institute and Professor of Surgery at Cleveland Clinic Lerner College of Medicine.

“I think everyone should have an MRI before these operations, and if there is evidence of prior injury or scar tissue, further assessment with neurocognitive testing is warranted,” he adds.

For some patients, that might mean the risks of surgery outweigh the benefits, Dr. Svensson notes, pointing out that a previous study had shown that such patients may have worse outcomes after TAVR.

A large randomized analysis

In the new study, published online in July by the Journal of Thoracic and Cardiovascular Surgery, 121 patients undergoing total aortic arch replacement over a 6.5-year period at Cleveland Clinic were randomized to either retrograde or antegrade brain perfusion during hypothermic circulatory arrest. Patients were evaluated clinically and with both brain MRI and neurocognitive testing — including measures of memory, learning and visuomotor coordination — preoperatively and at four to six months following surgery.

There were no significant differences in outcomes between the retrograde and antegrade perfusion groups. One patient (0.8 percent) died, but not from neurologic causes. In the 30-day postsurgical period, just one patient (0.8 percent) had a clinically evident stroke, two had visual changes, one had a seizure and five others had twitching or delirium.

Subclinical damage uncovered

However, of the 95 patients who underwent both pre- and postoperative brain imaging, 14 (15 percent) showed evidence of new infarcts or brain tissue changes. And of the 96 who underwent pre- and postoperative neurocognitive testing, 17 (18 percent) exhibited declines.

What’s more, abnormalities on one modality didn’t predict abnormalities on the other: Of the 10 patients with evidence of postsurgical changes on imaging who also underwent neurocognitive testing, just two showed decline. Of the 17 patients with neurocognitive decrements, 11 had neither imaging changes nor clinical events.

Implications for further research — and practice

While this study is one of the first to assess both MRI and neurocognitive function following total aortic arch replacement, several previous studies have used brain MRI in patients who have undergone TAVR, demonstrating embolic events in 70 to 80 percent. Fewer studies have used neurocognitive testing in this population, however.

Recent advances such as intraoperative brain perfusion, improvements to the “elephant trunk” procedure for aortic arch replacement (developed by Dr. Svensson and now widely adopted) and the use of filters to capture emboli from calcified valves in TAVR have reduced rates of clinical strokes and death to well below the 5 to 10 percent seen in studies from the previous decade.

In fact, the 0.8 percent mortality seen in this study was surprisingly low and may have resulted in a lack of statistical power to detect differences between the two perfusion methods, Dr. Svensson notes.

As new approaches are studied for both preventing and treating neurologic damage associated with these procedures, Dr. Svensson says the use of both MRI and neurocognitive testing will be essential to document their full impact, as well as to assess long-term implications of the subclinical events.

“We only looked at four to six months,” he notes. “Whether these subtle decrements will have a long-term effect we really don’t know.”