Changes in peak oxygen consumption on excercise and cardiomyopathy disease stage in Fabry disease

Abstract

Abstract Background Fabry disease (FD) is an X-linked lysosomal storage disorder manifesting as deficiency in the enzyme α-Galactosidase A (1) resulting in multi-organ accumulation of globotriaosylceramide (Gb3) (2) This causes predominantly cardiac, renal and cerebrovascular manifestations. Shortness of breath and exercise intolerance are common and can be related to multiple underlying mechanisms. Cardiopulmonary exercise testing (CPEX) quantifies aerobic fitness, functional capacity, chronotropic and haemodynamic response to exercise, and attributes effort intolerance to different aetiologies, including impaired cardiac and respiratory function. Purpose We hypothesise that there is progressive effort intolerance that reflects continual cardiac Gb3 accumulation, becoming common during myocardial hypertrophy and disabling in the fibrosis and inflammation stage. The aims of this study were to ascertain frequency and severity of exercise intolerance in FD by investigating the relationship between peak maximal oxygen uptake (VO2 max) and cardiac disease stage, quantified based on a four-point scale, as proposed in published literature (3). Methods This was a retrospective review of adults with FD and exercise intolerance attending a specialist clinic who had undergone either CPEX or six-minute walk testing (6MWT) in those less mobile. Biochemical, cardiac magnetic resonance (CMR) imaging and transthoracic echocardiographic (TTE) data were also collected. Results N=54 patients underwent CPEX and N=35 patient underwent 6MWT. Estimated peak VO2 max was calculated using 6MWD in those undergoing 6MWT. Median age was 54 (IQR 40-62) years and 53% were male. Patients were equally distributed across disease stage (1-4). There were significant trends in age (increasing) and gender (male predominance) from stage 1-4. Age/sex-normalised peak VO2 max values were calculated as per published literature due to the confounding effect of age and male gender. Mean normalised VO2 max was 35.5ml/kg/min for the cohort, an underperformance of 12.3 ± 8.0 ml/kg/min. The magnitude of underperformance began from stage 1 (no cardiomyopathy) and increased with each stage (Figure 1). Impairments in renal (creatinine and albumin: creatinine ratio) and cardiac biomarkers (troponin and N-terminal pro brain natriuretic peptide) was associated with reduced VO2 max (Table 1). Increased indexed left ventricular mass on CMR and impairments in atrial volume and function on TTE were also associated with a reduction in VO2 max (Table 1). Conclusion This study is the first of its kind to demonstrate impairments in peak aerobic capacity in adults with FD and no cardiomyopathy (stage 1) which impairs further with cardiac disease stage. Future work should focus on how disease-modifying therapy can target this using VO2 as an endpoint and marker of response.Normalised peak VO2 max + disease stageVO2 max and blood / imaging parameters