Cardiopulmonary Exercise Testing Identifies Treatable ATTR Cardiac Amyloidosis: Beyond Natriuretic Peptides.

BACKGROUND: Transthyretin cardiac amyloidosis (ATTR-CM) is a progressive infiltrative cardiomyopathy where early disease-modifying therapy improves outcomes. However, treatment access may be restricted by biomarker thresholds not reflecting true functional impairment. CASE SUMMARY: A 73-year-old man with exertional dyspnea (NYHA functional class II) and confirmed wild-type ATTR-CM did not meet reimbursement criteria for tafamidis because N-terminal pro-B-type natriuretic peptide was below the required threshold (≥600 pg/mL), despite impaired functional capacity on cardiopulmonary exercise testing (CPET). Acoramidis was obtained through expanded access. At 6-month follow-up, the patient showed clinical stability and improved exercise capacity. DISCUSSION: Fixed N-terminal pro-B-type natriuretic peptide cutoffs may exclude patients with early-stage heart failure who would benefit from treatment. CPET helps identify therapy candidates below biomarker thresholds. TAKE-HOME MESSAGES: CPET detects functional impairment in ATTR-CM even when natriuretic peptides remain low. Early transthyretin-stabilizer initiation in NYHA functional class I-II yields better outcomes; treatment eligibility should integrate functional assessment beyond biomarkers alone.