Transthyretin cardiac amyloidosis in patients with severe aortic stenosis undergoing transcatheter aortic valve replacement: experience of a single center.

Background: Even if prevalent among patients with severe aortic stenosis (AS), the clinical suspicion for transthyretin cardiac amyloidosis (ATTR-CA) remains difficult in this subset. We report our single center experience on ATTR-CA detection among TAVR candidates to provide insights on the prevalence and clinical features of dual pathology as compared to lone AS.

Methods: Consecutive severe AS patients undergoing transcatheter aortic valve replacement (TAVR) evaluation at a single center were prospectively included. Those with suspected ATTR-CA based on clinical assessment underwent ^99m Tc-3,3-diphosphono-1,2-propanodicarboxylic acid (DPD) bone scintigraphy. The RAISE score, a novel screening tool with high sensitivity for ATTR-CA in AS, was retrospectively calculated to rule-out ATTR-CA in the remaining patients. Patients were categorized as follow: "ATTR-CA+": patients with confirmed ATTR-CA at DPD bone scintigraphy; "ATTR-CA-": patients with negative DPD bone scintigraphy or a negative RAISE score; "ATTR-CA indeterminate": patients not undergoing ATTR-CA assessment with a positive RAISE score. The characteristics of ATTR-CA+ and ATTR-CA- patients were compared.

Results: Of 107 included patients, ATTR-CA suspicion was posed in 13 patients and confirmed in six. Patients were categorized as follow: 6 (5.6%) ATTR-CA+, 79 (73.8%) ATTR-CA-, 22 (20.6%) ATTR-CA indeterminate. Excluding ATTR-CA indeterminate patients, the prevalence of ATTR-CA was 7.1% (95% CI 2.6-14.7%). As compared to ATTR-CA - patients, ATTR-CA + patients were older, had higher procedural risk and more extensive myocardial and renal damage. They had higher left ventricle mass index and lower ECG voltages, translating into a lower voltage to mass ratio. Moreover, we describe for the first time bifascicular block as an ECG feature highly specific of patients with dual pathology (50.0% vs. 2.7%, P<0.001). Of note, pericardial effusion was rarely found in patients with lone AS (16.7% vs. 1.2%, P=0.027). No difference in procedural outcomes was observed between groups.

Conclusions: Among severe AS patients, ATTR-CA is prevalent and presents with phenotypic features that may aid to differentiate it from lone AS. A clinical approach based on routine search of amyloidosis features might lead to selective DPD bone scintigraphy with a satisfactory positive predictive value.