Introduction:Hypertrophic cardiomyopathy (HCM) is one of the most common cardiomyopathies in the world, and it’s also the main causes of cardiac sudden cardiac death (SCD) in young adults. Interstitial myocardial fibrosis is common in HCM patients and is one of the leading causes of ventricular arrhythmia. Interstitial myocardial fibrosis always causes ventricular remodeling, cardiac function changes and myocardial electrophysiology abnormality. It could also have an important relationship with SCD. At present, cardiac magnetic resonance (CMR) is considered currently to be the best way to evaluate cardiac structure and function, especially myocardial late gadolinium enhancement technique [1,2]. LGE-MR has some limitations in patients with diffused interstitial myocardial fibrosis [3]. T1-mapping imaging is a new method for evaluation of myocardial fibrosis, which can directly measure longitudinal relaxation time constant (T1) of myocardium and quantitatively assess myocardial damage. The native T1- mapping (pre-contrast T1) as a noninvasive method, not only can avoid renal toxicity, but also effectively evaluate myocardial fibrosis quantitatively and predict prognosis without gadolinium. This study is mainly to use a noninvasive imaging technique to evaluate the potential myocardial fibrosis in patients with HCM on the preliminary quantitative research. Methods: MR native T1-mapping imaging acquisition was performed on a 3.0T scanner (GE, HDxt) with Modified Look-Locker with Saturation Recovery (MOLLSR) technique, using 8 channel heart coils. 7 patients with HCM (4 male and 3 female, 41-82 years) and 6 healthy volunteers (4 female and 2 male, 23-37 years) were enrolled in the study. We mainly focused on left ventricular short axis myocardial T1-mapping imaging, including apex, mid and basal scanning slices. We manually delineated a ROI (0.6-1.0mm2) in the hypertrophy myocardium and the remote “normal” myocardium in patients for the same slice. We also measured the volunteers’ myocardium by the same method to obtain average native T1 values. The native T1-values were measured blindly by an experienced cardiac radiologist. Nonparametric test was performed to analyze the differences between hypertrophy myocardium and non-hypertrophy myocardium, normal myocardium. Statistical significance was defined less than 0.05. Results: In patients with HCM, native-T1 values of hypertrophy myocardium (1224.37ms±119.62ms) were higher than remote myocardium (1098.52ms±202.40ms) (p=0.08). At the same time, native-T1 values of hypertrophy myocardium (1224.37ms±119.62ms) were higher than normal volunteers (1005.55ms±100.30ms) (p=0.00). Native-T1 values between remote myocardium in patients with HCM (1098.52ms±202. 40ms) and normal volunteers (1005.55ms±100.30ms) had statistical significance (p=0.02). Discussion: The reasons of interstitial myocardial fibrosis in HCM are complex and 栀愀搀 not been fully explained. Some specific factors are also important, such as decreased capacity, anemia, continuous micro chronic infarct, microvascular remodeling, calcium and blood-flow disorders, hormones, etc. Because HCM patients may die of SCD, quantitative evaluation myocardial fibrosis in HCM patients could provide great values of predicting prognosis. As a new method to directly measure the myocardial tissue without contrast agents, Native T1-mapping imaging can be used to the native-T1mapping of left ventricular myocardium in patients with HCM. T1 values in patients with HCM was significant higher than that of normal volunteers, it may suggested that interstitial substance increase in HCM patients. And the T1 value of the non-hypertrophy myocardium in HCM is also higher than of normal volunteers, it may hit that the fibrosis of remote “normal” myocardium is developing, but the specific mechanism remains to be seen in our further research. Conclusion: Native T1-mapping as a noninvasive new method, can be used to quantitatively evaluate myocardial fibrosis in patients with HCM without using contrast agents.