Evaluation of flow through simulated vascular stenoses with gradient echo magnetic resonance imaging.

Magnetic resonance imaging using gradient echo sequences can quickly generate dynamic images of the cardiovascular system. We used a gradient echo sequence (repetition time = 21 milliseconds, echo time = 12 milliseconds, flip angle = 30 degrees) to evaluate how a simulated vascular stenoses affects the signal intensity of flowing fluid. Axial slices were obtained at regular intervals along a plastic tube containing a circular constriction (25%, 51%, or 73% reduction of cross-sectional area). Image data collected at each slice level were used to reconstruct 32 images evenly spaced in time over one cycle of pulsatile flow. Contrast ratios were calculated between signal intensities from tube lumen and surrounding stationary water jacket. Upstream from each stenosis, signal intensity increased during systole and decreased during diastole, paralleling the changes in velocity we measured with a flow probe. However, within the 51% and 73% stenoses and just beyond them, there were consistent decreases in systolic signal intensity. Flow through the 25% constriction had little effect on the signal intensity pattern. These results suggest that the gradient echo pulse sequence may be useful in evaluating disturbed flow associated with vascular stenoses.

The king of hearts: analysis of 23 patients with hearts weighing 1,000 grams or more.

Certain clinical and morphologic features are described in 23 patients in whom the heart at necropsy weighed at least 1,000 g (mean 1,106). The heart weight to body weight ratio ranged from 1.2 to 2.7 (normal 0.40). The 23 patients were derived from examination of the hearts of 7,671 patients with various cardiovascular disorders over a 25-year period. The massive cardiomegaly was the result of aortic regurgitation in 14 patients (61%): isolated in 8, associated with mitral regurgitation in 4, and with ventricular septal defect in 2. Three others (13%) had combined aortic valve stenosis and aortic regurgitation and 1 patient (4%) had mitral stenosis and regurgitation and mild aortic stenosis. Four patients (17%) had hypertrophic cardiomyopathy, and 1 patient (4%) had ventricular septal defect with mitral stenosis. They were 20 to 64 years old (mean 42) and 21 (91%) were men. Four patients at necropsy had 1 or more major coronary arteries narrowed more than 75% in cross-sectional area by atherosclerotic plaques, and only 4 patients had grossly visible left ventricular (LV) scars, 2 of whom had insignificant coronary narrowing. Examination of electrocardiograms in 17 of the 23 patients disclosed that Sokolow-Lyon criteria for LV hypertrophy was achieved in only 12 patients (71%) and Romhilt-Holt QRS voltage criteria faired even worse. Total 12-lead QRS voltage was more than 175 mm (10 mm = 1 mV) in 16 patients (94%) and it was more than 250 mm in 13 patients (76%). Total 12-lead QRS voltage in 17 patients ranged from 140 to 601 mm (mean 323). Measurement of the sum of the 12-lead QRS voltage may be quite useful in diagnosing LV hypertrophy by electrocardiogram.