Prevalence and Outcomes of Cardiac Amyloidosis in All-Comer Referrals for Bone Scintigraphy

Abstract

The prevalence of cardiac amyloidosis (CA) in the general population and associated prognostic implications remain poorly understood. We aimed to identify CA prevalence and outcomes in bone scintigraphy referrals. <b>Methods:</b> Consecutive all-comers undergoing ^99mTc-3,3-diphosphono-1,2-propanodicarboxylic-acid (^99mTc-DPD) bone scintigraphy between 2010 and 2020 were included. Perugini grade 1 was defined as low-grade uptake and grade 2 or 3 as confirmed CA. All-cause mortality, cardiovascular death, and heart failure hospitalization (HHF) served as endpoints. <b>Results:</b> In total, 17,387 scans from 11,527 subjects (age, 61 ± 16 y; 63.0% women, 73.6% cancer) were analyzed. Prevalence of ^99mTc-DPD positivity was 3.3% (<i>n</i> = 376/11,527; grade 1: 1.8%, grade 2 or 3: 1.5%), and was higher among cardiac than noncardiac referrals (18.2% vs. 1.7%). In individuals with more than 1 scan, progression from grade 1 to grade 2 or 3 was observed. Among patients with biopsy-proven CA, the portion of light-chain (AL)-CA was significantly higher in grade 1 than grade 2 or 3 (73.3% vs. 15.4%). After a median of 6 y, clinical event rates were: 29.4% mortality, 2.6% cardiovascular death, and 1.5% HHF, all independently predicted by positive ^99mTc-DPD. Overall, adverse outcomes were driven by confirmed CA (vs. grade 0, mortality: adjusted hazard ratio [AHR] 1.46 [95% CI 1.12–1.90]; cardiovascular death: AHR 2.34 [95% CI 1.49–3.68]; HHF: AHR 2.25 [95% CI 1.51–3.37]). One-year mortality was substantially higher in cancer than noncancer patients. Among noncancer patients, also grade 1 had worse outcomes than grade 0 (HHF/death: AHR 1.45 [95% CI 1.01–2.09]), presumably because of longer observation and higher prognostic impact of early infiltration. <b>Conclusion:</b> Positive ^99mTc-DPD was identified in a substantial number of consecutive ^99mTc-DPD referrals and associated with adverse outcomes.