Functional capacity and ventilatory efficiency across atrial fibrillation subtypes in transthyretin amyloid cardiomyopathy
A Koesters, N Ermolaev, B Gregshammer, M Eslami, R Rettl, L Lichtblau, C Kronberger, L Schmid, M Poledniczek, R Badr Eslam, C SchukroAbstract
Background
Atrial fibrillation (AF) is common in transthyretin amyloid cardiomyopathy (ATTR-CM) and may contribute to reduced functional capacity and impaired cardiopulmonary exercise performance. The relationship between AF subtype and objective functional and ventilatory parameters in ATTR-CM remains incompletely characterized.
Objective
To assess differences in functional capacity and ventilatory efficiency across AF subtypes in patients with ATTR-CM.
Methods
This prospective, single-center study included patients with ATTR-CM (wild-type and hereditary) enrolled from 2018 to the present. AF status was categorized as I) no AF, II) paroxysmal AF, or III) permanent AF. Functional capacity and cardiopulmonary exercise parameters were assessed using the 6-minute walk test (6MWT), maximal workload (W), peak oxygen uptake (peak VO₂), and ventilatory efficiency (VE/VCO₂ slope). Between-group comparisons were performed using the Kruskal–Wallis test.
Results
A total of 169 patients with ATTR-CM were included. Functional capacity differed significantly across AF subtypes. Median 6MWT distance was 438.5 m (IQR 363–520) in patients without AF, 315 m (IQR 268.5–414.5) in paroxysmal AF, and 372 m (IQR 305–450) in permanent AF (p=0.0004). Maximal workload was higher in patients without AF (90 W, IQR 70–110) compared with paroxysmal (65 W, IQR 49–90) and permanent AF (63 W, IQR 49–90) (p=0.0009). Peak VO₂ was also higher without AF (16.35 mL·kg⁻¹·min⁻¹, IQR 12.4–20.0) than with paroxysmal (13.8, IQR 10.6–16.4) or permanent AF (13.7, IQR 11.5–15.8) (p=0.0044). Ventilatory efficiency differed across AF subtypes, with VE/VCO₂ slope 34.04 (IQR 31.28–40.65) in no AF, 39.41 (IQR 34.06–45.43) in paroxysmal AF, and 39.97 (IQR 36.17–43.15) in permanent AF (p=0.0008).
Conclusion
In this prospective ATTR-CM cohort, AF subtype was associated with significant differences in functional capacity, exercise performance, and ventilatory efficiency. Compared with patients without AF, those with paroxysmal or permanent AF demonstrated lower 6MWT distance, reduced maximal workload and peak VO₂, and higher VE/VCO₂ slope, consistent with greater functional limitation and impaired ventilatory efficiency in ATTR-CM.For image description, please refer to the figure legend and surrounding text.