AIMS: Amyloid cardiomyopathy is caused by the deposition of light chain (AL) or transthyretin amyloid (ATTR) fibrils, that leads to a restrictive cardiomyopathy, often resulting in heart failure (HF) with preserved or reduced ejection fraction. This study aimed to determine whether cardiac output reduction or ventilation inefficiency plays a predominant role in limiting exercise in patients with amyloid cardiomyopathy. METHODS: We conducted a multicentre prospective study in patients with AL or ATTR cardiomyopathy who underwent cardiopulmonary exercise testing across four centres. Patients were compared with a propensity-score matched HF cohort based on age, gender, left ventricular ejection fraction (LVEF), and peak oxygen consumption (VO RESULTS: Data from 267 amyloid patients aged 77 (72, 81) years, 86% male, with a median N-terminal pro B-type natriuretic peptide (NT-proBNP) of 2187 (1140, 4383) ng/L, exercise parameters of peak VO CONCLUSIONS: A higher VE/VCO