Aortic Stenosis and Cardiac Amyloidosis: A Pragmatic, Streamlined International

Calcific aortic stenosis (AS) and transthyretin (ATTR) cardiac amyloidosis are both conditions commonly affecting the elderly. Bone scintigraphy using amyloid-avid tracers (99mTc-3,3-diphosphono-1,2-propanodicarboxylic acid, DPD; 99mTc-pyrophosphate; or 99mTc-hydroxymethylene diphosphonate) represents the key imaging modality for non-invasive ATTR diagnosis. Recent studies have used this technology to screen AS patients and demonstrated that AS and ATTR may coexist in 8 to 16%. This is substantially higher than in non-cardiac referrals for bone scintigraphy (range 1-3% in individuals >80 years), which is considered the most accurate approach to estimate the ATTR prevalence in the general population. While the dual burden of AS and ATTR might suggest adverse prognostic implications, it has been shown that AS-ATTR and lone AS patients benefit equally from transcatheter aortic valve replacement (TAVR) with comparable 1- and 2-year survival rates. Yet, data on long-term outcomes are still missing.

With increased recognition and valvular treatment of AS-ATTR, the disease course after TAVR becomes a key issue. Our data suggest significantly different remodeling between lone AS and AS-ATTR, with the latter being transformed into a "lone-ATTR" cardiomyopathy phenotype at one-year post-TAVR. Novel ATTR-specific treatments are now available, with the potential to further improve prognosis in AS-ATTR on top of valvular replacement. However, patients with significant AS were not included in the ATTR-ACT trial, and treatment effectiveness in this patient population therefore remains unclear. Also, despite increased ATTR screening globally, the case numbers for dual AS-ATTR of individual centers are still low.

The present international multi-center study is therefore designed to provide detailed characterization of dual AS-ATTR, inform about long-term clinical outcomes and assess the effect of ATTR specific treatment.