[Changes in gadolinium-DTPA enhanced magnetic resonance signal intensity ratio in hypertrophic cardiomyopathy].

Serial gadolinium-diethylene-triamine-pentaacetic acid (Gd-DTPA) enhanced magnetic resonance (MR) signal intensity ratios were measured in 6 normal subjects and 20 hypertrophic cardiomyopathy (HCM) patients to try to differentiate normal from disorganized myocardial tissue. Images were obtained at 10-minute intervals 5-60 minutes after Gd-DTPA (0.1 mmol/kg) injection. The signal intensity ratio (myocardial signal intensity/skeletal muscle signal intensity) was measured at both hypertropic and nonhypertrophic regions in each image at the apex and mid-ventricular levels. The signal intensity ratio was standardized to compare each case. Hypertrophic myocardium was classified into two types. Type I in 11 of 20 patients was visualized as a homogeneous image, while type II in the other 9 patients was revealed as a mixed isointensity and high intensity area. The peak value of the standardized signal intensity ratio at the apex level was 1.28 +/- 0.09 in HCM patients and 1.23 +/- 0.06 in normal subjects, and at the mid ventricular level was 1.26 +/- 0.07 in hypertrophic regions, 1.17 +/- 0.12 in non-hypertrophic regions, and 1.16 +/- 0.07 in normal subjects. Thirty minutes after Gd injection, the standardized signal intensity ratio at the apex level was 1.21 +/- 0.08 in HCM patients and 1.07 +/- 0.08 in normal subjects, and those at the mid ventricular level was 1.20 +/- 0.09 in hypertrophic regions, 1.11 +/- 0.11 in non-hypertrophic regions, and 1.04 +/- 0.06 in normal subjects. The delayed decay of the signal intensity ratio and high signal intensity ratio in Gd-DTPA enhanced MR images are useful in myocardial tissue characterization in hypertrophic cardiomyopathy.