AIMS: Cardiac transthyretin (ATTR) amyloidosis is an increasingly recognized, progressive, and fatal cardiomyopathy, the natural history of which remains unclear. We sought to establish and validate a new prognostic staging system applicable to patients with both wild-type ATTR (ATTRwt) and hereditary variant ATTR (ATTRv) amyloid cardiomyopathy.
METHODS AND RESULTS: Eight hundred and sixty-nine patients with cardiac ATTR amyloidosis (553 with ATTRwt and 316 with ATTRv) attending the UK National Amyloidosis Centre were stratified into three disease stages at baseline on the basis of cut points in two universally measured biomarkers, N-terminal pro-B-type natriuretic peptide (NT-proBNP) and estimated glomerular filtration rate (eGFR). Stage I was defined as NT-proBNP ≤3000 ng/L and eGFR ≥45 ml/min, Stage III was defined as NT-proBNP >3000 ng/L and eGFR <45 ml/min, and the remainder were Stage II. The staging system was validated in a cohort of 318 patients with cardiac ATTR amyloidosis from France. Median survival among 393 (45%) Stage I patients was 69.2 months, 334 (38%) Stage II patients was 46.7 months, and 142 (16%) Stage III patients was 24.1 months (P < 0.0001). After adjusting for age, compared with Stage I, the hazard ratio (HR) for death for Stage II was 2.05 [confidence interval (CI) 1.54-2.72, P < 0.001] and for Stage III was 3.80 (CI 2.73-5.28, P < 0.001). HRs and statistical significance were little altered by transthyretin genotype and were maintained in the validation cohort.
CONCLUSION: This simple, universally applicable staging system stratifies patients with both ATTRwt and ATTRv amyloid cardiomyopathy into prognostic categories. It will be of value in the design of forthcoming clinical trials of novel amyloid-specific therapies.