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Exercise limitations in amyloid cardiomyopathy assessed by cardiopulmonary exercise testing-A multicentre study
Robin Willixhofer1, Mauro Contini2, Michele Emdin3
1Division of Cardiology, Department of Internal Medicine II, Medical University of Vienna, Vienna, Austria.
Insights
Ventilation inefficiency, indicated by a higher minute ventilation to carbon dioxide production (VE/VCO2) slope, limits exercise in patients with amyloid cardiomyopathy more than cardiac output reduction. Transthyretin amyloid (ATTR) cardiomyopathy may cause more severe exercise limitations than light chain (AL) amyloidosis.
Area of Science:
- Cardiology
- Pulmonology
- Exercise Physiology
Background:
- Amyloid cardiomyopathy, caused by light chain (AL) or transthyretin amyloid (ATTR) fibril deposition, leads to restrictive cardiomyopathy and heart failure (HF).
- Exercise limitation in amyloid cardiomyopathy is poorly understood, with uncertainty regarding the predominant role of cardiac output reduction versus ventilation inefficiency.
Purpose of the Study:
- To determine whether cardiac output reduction or ventilation inefficiency is the primary factor limiting exercise in patients with amyloid cardiomyopathy.
- To compare exercise limitation between AL and ATTR amyloidosis subtypes.
Main Methods:
- A multicenter prospective study involving patients with AL or ATTR amyloid cardiomyopathy who underwent cardiopulmonary exercise testing.
- Propensity-score matching was used to compare amyloid patients with a heart failure (HF) cohort based on age, gender, left ventricular ejection fraction (LVEF), and peak oxygen consumption (VO2).
Main Results:
- Amyloid patients exhibited a significantly higher VE/VCO2 slope and an earlier anaerobic threshold (AT) compared to the matched HF cohort, indicating greater ventilation inefficiency.
- Amyloid patients also showed higher NT-proBNP levels and peak ventilation, with reduced peak VO2 at AT.
- Within the amyloid group, transthyretin amyloid (ATTR) patients displayed a higher VE/VCO2 slope and earlier AT compared to light chain (AL) amyloid patients, suggesting more severe exercise limitations.
Conclusions:
- Ventilation inefficiency, evidenced by a higher VE/VCO2 slope and earlier AT, is a key determinant of functional capacity impairment in amyloid cardiomyopathy.
- ATTR amyloidosis may be associated with more pronounced exercise limitations compared to AL amyloidosis.
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 (VO2).
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 VO2 of 14.1 (11.6;16.9) mL/min/kg, a minute ventilation to carbon dioxide production (VE/VCO2) slope of 37.4 (32.5, 42.6) and a LVEF of 50% (44%, 59%) were analysed. We identified 251 amyloid cardiomyopathy-HF matches. Amyloid patients had a signifnicantly higher VE/VCO2 slope [37.4, inter quartile range (IQR): 32.7, 43.1 vs. 32.1, IQR: 28.7, 37.0, P < 0.0001], NT-proBNP (2249, IQR: 1187, 4420 vs. 718, IQR: 405, 2161 ng/L, P < 0.001), peak heart rate (121 ± 28 vs. 115 ± 27 beats/min, P = 0.007) and peak ventilation (51, IQR: 42, 62 vs. 43, IQR: 33, 53 L/min, P < 0.0001) with earlier anaerobic threshold (VO2 at AT: 8.9, IQR: 6.8, 10.8 vs. 10.8, IQR: 8.9, 12.7 mL/min/kg, P < 0.0001) compared with HF. Between amyloid patients, AL patients (n = 27) were younger (63, IQR: 58, 70 vs. 78, IQR: 72, 81 years, P < 0.0001), had lower VE/VCO2 slope (35.0, IQR: 30.0, 38.7 vs. 38.0, IQR: 32.8, 43.1, P = 0.019), higher end-tidal carbon dioxide partial pressure both at AT (35.1 ± 4.8 vs. 31.4 ± 4.7 mmHg, P < 0.001) and peak exercise (32, IQR: 28, 35 vs. 30, IQR: 26, 33 mmHg, P = 0.039) as compared with ATTR (n = 233).
Conclusions:
A higher VE/VCO2 slope and an earlier AT, determining functional capacity impairment, was assessed in patients with amyloid cardiomyopathy compared with the matched HF cohort. Additionally, patients with ATTR might display more severe exercise limitations as compared with AL.
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