Determining the Association of TTR Stabilizing Therapy With Circulating TTR Amyloid Aggregates Over Time in Patients With ATTR-CM: Longitudinal Biomarker Study

Inclusion Criteria: * Men and women ages 30-80 who have symptomatic ATTR-CA as determined by a history of HF (this will be assessed by study personnel and defined as : 1) history of hospitalization within the previous 12 months for management of HF; 2) an elevated B-type natriuretic peptide level ≥100 pg/mL or NT-proBNP ≥360 pg/mL within the previous 12 months; or 3) a clinical diagnosis of HF from a treating clinician) * ATTR-CA previously diagnosed histologically by amyloid staining and tissue typing with immunohistochemistry or mass spectrometry or by bone scintigraphy in without abnormal M-protein * TTR gene sequencing confirming the TTR genotype has resulted or is pending * Enrollment will be stratified by n/N=30/50 starting on-label TTR-stabilizing therapy (e.g. tafamidis) within 5 days after enrollment or by n/N=20/50 of those currently taking TTR-stabilizing therapy Exclusion Criteria: * Other known causes of cardiomyopathy * History of light-chain cardiac amyloidosis * Cardiac transplantation * Liver transplantation * Has taken patisiran in the past 90 days, or inotersen in the past 180 days, has ever taken vutrisiran, or is participating in a clinical trial for ATTR treatments * Estimated glomerular filtration rate ≤30 mL/min/1.73 m2 * Anticipated gaps in ATTR-CA treatment for 3 months after enrollment