Changes in peak oxygen consumption in Fabry disease and associations with cardiomyopathy severity.

Background: Fabry disease (FD) causes multiorgan sphingolipid accumulation, with cardiac involvement responsible for the largest burden of morbidity and mortality. Exercise intolerance in FD is prevalent, yet the mechanisms of this are poorly understood. The aim of this study was to assess exercise intolerance in FD and identify whether this correlates with the phase of cardiomyopathy.

Methods: This was a retrospective observational study of adults with FD undergoing cardiopulmonary exercise testing (CPEX) between September 2011 and September 2023 at a national referral centre in the UK. The primary outcome measure was peak oxygen uptake (V̇O_2peak), with forced expiratory volume in 1 s (FEV₁) used to quantify respiratory impairment. Age-normalised/sex-normalised values were additionally calculated, based on published normal ranges for subgroups of age and sex. The cardiomyopathy phase was classified on a 4-point scale by two FD experts using contemporaneous imaging and biochemistry results.

Results: CPEX was completed by 42 patients, with a median age of 54 years and of whom 62% were male. Patients were approximately equally distributed across the four cardiomyopathy phases. At phase I, the mean (±SD) V̇O_2peak was 28.7±7.7 mL/kg/min, which represented a significant underperformance of 23%, relative to age-normalised and sex-normalised values (expected mean: 37.3±3.2 mL/kg/min, p=0.006). V̇O_2peak declined significantly across the cardiomyopathy phases (p=0.010), reaching a mean of 21.2±6.1 mL/kg/min at phase IV. Normalised FEV₁ was not found to show a corresponding significant change with cardiomyopathy phase (p=0.683). Impaired left atrial global longitudinal strain as well as biochemical markers of inflammation were associated with impaired V̇O_2peak.

Conclusions: This study identifies significantly impaired aerobic capacity in FD, even in those without phenotypic cardiomyopathy. No corresponding changes in respiratory impairment were observed, suggesting that exercise intolerance may be due to early cardiac sphingolipid accumulation and subsequent atrial and ventricular dysfunction, which increases as cardiomyopathy progresses. As such, peak V̇O_2peak holds promise as a therapeutic marker of response to FD-specific therapy.