Clinical significance of abnormal high signal intensity of left ventricular myocardium by gadolinium-diethylenetriaminepenta-acetic acid enhanced magnetic resonance imaging in hypertrophic cardiomyopathy

The significance of abnormal high signal intensity observed in left ventricular myocardium by gadolinium-diethylenetriaminepenta-acetic acid (Gd-DTPA) enhanced magnetic resonance (MR) imaging in hypertrophic cardiomyopathy (HCM) patients was assessed by comparison with T1-weighted MR imaging, thallium-201 (201Tl) myocardial scintigraphy, radionuclide angiocardiography, M-mode echocardiography, electrocardiography, and chest radiography. The 16 patients were divided into three groups: 8 patients (group I) with abnormal high signal intensity before and after Gd-DTPA enhancement, 4 (group II) with abnormal high signal intensity only after enhancement and 4 (group III) without abnormal high signal intensity. Thallium-201 myocardial single photon emission computed tomography (SPECT) showed abnormalities of regional 201Tl uptake in the left ventricular myocardium in 4 patients in Group I, 3 in group II, and one in Group III. No significant difference in left ventricular ejection fraction (LVEF) was seen between groups I, II, and III (64±13%, 67±17% and 71±7%) although 3 patients in group I had LVEF of less than 55%. Left ventricular peak filling rates (PFR) of groups I and II were significantly lower than group III (1.90±0.44, 2.41±0.43 and 3.37±0.48 EDV/sec). Group I had larger end-diastolic left ventricular dimension (LVDd), significantly larger end-systolic left ventricular dimension (LVDs), and smaller % fractional shortening (%FS) than group III (49±4 vs 42±6 mm, 31±5 vs 22±4 mm, and 38±8 vs 49±4%). Abnormal high signal intensity in left ventricular myocardium in HCM seems to reflect myocardial ischemia and fibrosis due to small vessel disease, or myocardial degeneration and necrosis. We conclude that Gd-DTPA enhanced MR imaging may detect the early process of the dilated phase of HCM. (J.P.N.)