More, Larger Brain Lesions on MRI After
Bicuspid TAVR

Patrice Wendling

December 03, 2020

Diffusion-weighted MRI points to more silent brain injuries after transcatheter aortic valve replacement (TAVR) of bicuspid aortic valves (BAVs) in a single-center study.

Although TAVR has been shown to be feasible for stenotic BAVs, the jury is still out on whether it's the best approach for this challenging morphology. Because BAV patients were excluded from pivotal TAVR trials, data remain limited but suggest a higher 30-day stroke risk than with tricuspid aortic valves (TAVs).

The present study, including 204 consecutive Chinese patients undergoing TAVR, is consistent with this observation, reporting an overt stroke rate of 2.4% in BAV patients and 1.7% in TAV patients.

The incidence of new ischemic cerebral lesions was also comparable (84.3% vs 76%), but that's where the similarities appear to stop.

BAV patients undergoing TAVR had more new lesions (median, 4 vs 2; P = .008), higher total new lesion volumes (290 mm3 vs 140 mm3; P = .008), and nearly three times the number of lesions larger than 1 cm3 (28.6% vs 10.9%; P = .005).

Independent risk factors influencing the number of new lesions were BAV, prosthetic valve type, age, left ventricular ejection fraction, post-dilatation, and procedure duration.

"Our study has demonstrated that patients with stenotic BAVs undergoing TAVR may experience more severe brain injuries both in terms of the number of lesions and larger lesion size than those with TAV disease," Jiaqi Fan, MD, Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China, told | Medscape Cardiology via email.

The procedural complexity in BAV patients with longer procedure duration and higher post-dilatation frequency may add to the risk of cerebral injury by increasing the number of new ischemic lesions on diffusion-weighted MRI (DW-MRI), the investigators suggest.

"Moreover, heavy calcification could also increase the risk of small debris originating from the calcified native aortic valve, causing heavier damage in the younger BAV patients," they write in the article, published this week in the Journal of the American College of Cardiology.

In an accompanying editorial, Marc Radermecker, MD, PhD, Sart-Tilman University Hospital Center, Liège, Belgium, and colleagues, however, argue that with the availability of T3-DW-MRI today, new silent lesions can be detected in most, if not all, patients undergoing TAVR.

"The tissue-based paradigm for [central nervous system] CNS injury assessment therefore raises major concerns with regard to the significance of these so called 'silent' or 'covert' brain injuries," they write.

Fan and colleagues acknowledge new ischemic lesions have been found in 74% to 100% of patients on DW-MRI after TAVR. Though some studies have shown they aren't linked to apparent neurologic symptoms, "there is evidence that perioperative ischemia may increase the risk of cognitive function and long-term dementia."

The present study is the first to provide insights into the risk of brain injury on DW-MRI after TAVR in BAV patients. The 83 BAV patients were younger than the 121 TAV patients (median, 76 vs 79 years), had lower Society of Thoracic Surgeons scores (4.87 vs 6.38), and were less likely to have had a prior stroke (1.2% vs 8.3%).

Post-dilatation was used in 63.9% of BAV patients and 48.8% of TAV patients; procedure duration was 60 minutes vs 53 minutes. Brain DW-MRI was performed before and within 5.7 days after TAVR.

No significant difference was found in the number, total volume, and volume per lesion between BAV raphe types 0 and 1. The former comprised 67% of the BAV patients, whereas raphe type 1 is more common in European and Western countries.

Asked about the lack of difference between the two groups, Fan speculated that the comparable frequency of post-dilatation in type 0 and type 1 BAV patients (67.9% vs 55.6%, P = .332), similar age (75 vs 78 years; P = .180), and comparable calcium volume scores (949.1 vs 966.4 mm3; P = .800) may be responsible, but that the finding should be confirmed by a larger clinical trial.

As to the generalizability of the overall results, Fan said. "Although we provided the data from an Asian population with a higher prevalence of type 0 BAV patients, we also revealed the higher brain injury in type 1 BAV patients."

The age of the participants was also similar to that in a recent study of 1034 BAV patients from 24 cardiovascular centers across eight non-Asian countries, he noted. "Furthermore, the incidence of stroke after TAVR in these 1034 BAV patients was similar between different valve morphology group, which is consistent with the stroke incidence in our study."

In Fan's study, two BAV patients experienced a nondisabling stroke and two TAV patients had a disabling stroke before discharge.

Modified Rankin Scale scores were comparable between the two groups at baseline (P = .096) and 1 year (P = .482).

No commercial cerebral protection devices have been approved in China, but such devices may be recommended for TAVR, especially in BAV patients, to avoid ischemic lesions that could deteriorate neurologic and cognitive function, Fan and colleagues said.

Long-term follow-up is required for mortality, stroke, neurologic, and cognitive function outcomes, they noted. Other study limitations are the single-center, nonrandomized design and the potential for bias by excluding clinically worse-off patients unable to tolerate MRI.

Radermecker agreed with the recommendation for cerebral protection but suggested that specific device improvements and procedural refinements are needed as well.

"Finally, we concur as physicians with the cautious indications for TAVR in patients with BAVs as implicitly suggested here," the editorialists write.

Although not exempt from central nervous system injury, the option of modern surgical aortic valve replacement (SAVR), which may guarantee a properly fixed prosthesis and management of associated BAV disease, is both efficient and currently performed mini-invasively, Radermecker and colleagues assert. "These 2 features confer the high value of SAVR in selected patients with BAVs without compromising late outcome."

Study coauthor Martin B. Leon has served as a nonpaid scientific advisory board member for Edwards Lifesciences and as a consultant to Abbott Vascular and Boston Scientific. All other authors and the editorialists have disclosed no relevant financial relationships.

J Am Coll Cardiol. Published online December 1, 2020. Full text, Editorial

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