Myocardial tissue characterization using magnetic resonance noncontrast t1 mapping in hypertrophic and dilated cardiomyopathy.

BACKGROUND Noncontrast magnetic resonance T1 mapping reflects a composite of both intra- and extracellular signal. We hypothesized that noncontrast T1 mapping can characterize the myocardium beyond that achieved by the well-established late gadolinium enhancement (LGE) technique (which detects focal fibrosis) in both hypertrophic (HCM) and dilated (DCM) cardiomyopathy, by detecting both diffuse and focal fibrosis. METHODS AND RESULTS Subjects underwent Cardiovascular Magnetic Resonance imaging at 3T (28 HCM, 18 DCM, and 12 normals). Matching short-axis slices were acquired for cine, T1 mapping, and LGE imaging (0.1 mmol/kg). Circumferential strain was measured in the midventricular slice, and (31)P magnetic resonance spectroscopy was acquired for the septum of the midventricular slice. Mean T1 relaxation time was increased in HCM and DCM (HCM 1209±28 ms, DCM 1225±42 ms, normal 1178±13 ms, P<0.05). There was a weak correlation between mean T1 and LGE (r=0.32, P<0.001). T1 values were higher in segments with LGE than in those without (HCM with LGE 1228±41 ms versus no LGE 1192±79 ms, P<0.01; DCM with LGE 1254±73 ms versus no LGE 1217±52 ms, P<0.01). However, in both HCM and DCM, even in segments unaffected by LGE, T1 values were significantly higher than normal (P<0.01). T1 values correlated with disease severity, being increased as wall thickness increased in HCM; conversely, in DCM, T1 values were highest in the thinnest myocardial segments. T1 values also correlated significantly with circumferential strain (r=0.42, P<0.01). Interestingly, this correlation remained statistically significant even for the slices without LGE (r=0.56, P=0.04). Finally, there was also a statistically significant negative correlation between T1 values and phosphocreatine/adenosine triphosphate ratios (r=-0.59, P<0.0001). CONCLUSIONS In HCM and DCM, noncontrast T1 mapping detects underlying disease processes beyond those assessed by LGE in relatively low-risk individuals.