Cardiac Phenotype of Prehypertrophic Fabry Disease.

Background: Fabry disease (FD) is a rare and treatable X-linked lysosomal storage disorder. Cardiac involvement determines outcomes; therefore, detecting early changes is important. Native T1 by cardiovascular magnetic resonance is low, reflecting sphingolipid storage. Early phenotype development is familiar in hypertrophic cardiomyopathy but unexplored in FD. We explored the prehypertrophic cardiac phenotype of FD and the role of storage. Methods and Results: A prospective, international multicenter observational study of 100 left ventricular hypertrophy-negative FD patients (mean age: 3915 years; 19% male) and 35 age- and sex-matched healthy volunteers (mean age: 40 +/- 14 years; 25% male) who underwent cardiovascular magnetic resonance, including native T1 and late gadolinium enhancement, and 12-lead ECG. In FD, 41% had a low native T1 using a single septal region of interest, but this increased to 59% using a second slice because early native T1 lowering was patchy. ECG abnormalities were present in 41% and twice as common with low native T1 (53% versus 24%; P=0.005). When native T1 was low, left ventricular maximum wall thickness, indexed mass, and ejection fraction were higher (maximum wall thickness 9 +/- 1.5 versus 8 +/- 1.4 mm, P<0.005; indexed left ventricular mass 63 +/- 10 versus 58 +/- 9 g/m(2), P<0.05; and left ventricular ejection fraction 73 +/- 8% versus 69 +/- 7%, P<0.01). Late gadolinium enhancement was more likely when native T1 was low (27% versus 6%; P=0.01). FD had higher maximal apical fractal dimensions compared with healthy volunteers (1.27 +/- 0.06 versus 1.24 +/- 0.04; P<0.005) and longer anterior mitral valve leaflets (23 +/- 2 mm versus 21 +/- 3 mm; P<0.005). Conclusions: There is a detectable prehypertrophic phenotype in FD consisting of storage (low native T1), structural, functional, and ECG changes.