Fabry disease (FD) is an X chromosome-linked genetic disease, and leading to deficient alpha-galactosidase A (α-Gal A) activity. The deficiency results in glycosphingolipids storage disorder and causes dysfunctions in organs, such as kidney, heart and other nervous systems. Among all types of FD, cardiac manifestation is the most difficult to be diagnosed because of remaining α-Gal A activity, which can keep partial lipid metabolism while comparing to other types without lipid metabolism. Clinical symptoms finally appear and decrease life quality and lifespan of the patients gradually. Early diagnosis of cardiomyopathy has become crucial to allow effective treatment and prevent cardiovascular complications.¹ Therefore, the purpose of this study is to use the MR tissue phase mapping technique on asymptomatic FD patients to detect possible myocardiac dysfunction.The study recruited 7 patients who were genetically diagnosed as FD (54.1 ± 11.8 y/o; male/female: 4/3; BSA (body surface area): 1.6 ± 0.2 m²) and 22 normal subjects (22.2 ± 2.0 y/o; male/female: 16/11; BSA: 1.7 ± 0.2 m²) without any type of the factor of high risk in cardiac dysfunction. All subjects were examined using 3.0 Tesla MR scanners (Tim Trio or Skyra, Siemens, Erlangen, Germany). ECG-triggering (acquiring 90% of cardiac cycle) and navigator echo technique were performed to synchronize the cardiac and respiratory motion respectively during free-breathing acquisitions. For acquisition of the myocardial wall motion velocity, the imaging planes were placed on three short axis slices (Fig. 1)² and evaluated by three-directionally velocity encoded phase-contrast MRI with dark-blood technique: TR/TE = 26/4.2 ms, pixel size = 1.17 x 1.17 mm² , slice thickness = 6 mm, flip angle = 7°, Venc in-plane = 15 cm/s and Venc through-plane = 25 cm/s. Post-processing was performed on a self-developed program. LV was divided into 16 segments, and RV was divided into 10 segments. To quantify the global and regional cardiac function, different orientation, Vr (radial velocity) and Vz (longitudinall velocity) index of myocardium, time-to-peak (TTP) and amplitude of velocity(AMP) (Fig. 2), in diastole and systole were used to show the difference between normal group and FD group.Table1 shows the numbers of significantly different segments in LV and RV between two groups. The preliminary results demonstrated significantly longer TTP and lower AMP in FD group. Especially, amplitude of Vz during diastole (LV : 9.3 ± 2.3 vs. 5.3 ± 1.3 cm/s ; RV : 7.7 ± 1.7 vs.4.5 ± 1 cm/s) (Fig. 3) and systole (LV : -5.9 ± 1.3 vs. -3.9 ± 0.9 cm/s) exhibited prominent differences between two groups. In addition, amplitude of Vr in diastole (LV : -5.1 ± 0.7 vs. -3.7 ± 0.5 cm/s) also showed apparent differences , thus indicating deteriorated myocardial function in FD group. The significant results were highlighted by gray boxes (Table1). The FD group also revealed reduced AMP in basal, mid, and apical parts of LV, thereby showing worsened regional function.Pieroni et al mentioned that Fabry cardiomyopathy is characterized by reduced myocardial contraction and relaxation by tissue Doppler velocities,¹ and the same results are shown in this study using MR. Weidemann et al had shown that tissue Doppler imaging and contractility assessment by strain-rate imaging documented a substantial decrease in contractile performance, occurring earlier in the longitudinal (Vz) than in the radial dimension (Vr) .³ This study finds similar significant differences in various segments between groups. As previously reported, FD patients have normal global LV function but with impaired regional myocardial function when in early stage.³ Therefore, it is important for regional myocardium function detection. In addition, MRI is advantageous when comparing with echocardiography; which suffers from limitations; regarding inter-observer variability and detecting only the component of velocity directed to or from the transducer.¹ In conclusion, longer TTP and lower AMP revealed by TPM analysis in FD patients suggested the potential of preclinical MR diagnosis in segmental myocardial motion velocity.