ECHOCARDIOGRAPHIC PATTERNS OF MYOCARDIAL FIBROSIS IN HYPERTENSIVE PATIENTS - ENDOMYOCARDIAL BIOPSY VERSUS ULTRASONIC TISSUE CHARACTERIZATION

Echocardiographic image texture has been demonstrated to reflect the p hysical properties of the tissue under examination. To evaluate the ro le of collagen in determining the echo pattern of the left ventricular wall, we studied nine hypertensive patients with left ventricular hyp ertrophy (left ventricular mass index > 125 gm/m(2)) and biopsy-proven different degrees of myocardial fibrosis by analyzing the echocardiog raphic examinations performed before the biopsy. Myocardial tissue was sampled under fluoroscopy and two-dimensional echo guidance in the in terventricular septum. Collagen volume fraction (CVP; normal, range up to 2%) was taken as an index of fibrosis. The echo patterns were asse ssed by analyzing standard two-dimensional parasternal long-axis echoc ardiograms recorded on videotape. Images were color-coded at 256 level s (0 = yellow, 256 = black) and digitized off-line onto a personal com puter. The region of analysis was set using a selection tool (20 x 10 mm) in the general area of septum where the specimen was taken. For ea ch selection a color-level histogram, representing the frequency distr ibution, was derived with estimates of the average pixel intensity (mC S), skewness (SR), kurtosis (K), and the broad band (Bb) of the echoes about the distribution. Echo-derived parameters in each patient were compared with corresponding CVF values. CVF was out of range in all pa tients, ranging from 2.6% to 7.6% (mean 4.3% +/- 1.6%). No correlation was found between CVF and mCS, whereas a significant correlation was found at end diastole between CVF and the parameters describing histog ram morphology, respectively, SK (r = 0.73), K (r = 0.69), Bb (r = 0.7 2). These findings for the first time demonstrate in vivo in hypertens ive patients with left ventricular hypertrophy an agreement between ec ho amplitude and histologically assessed collagen volume. Thus in our studied patients collagen content appears to be the major determinant of regional echo intensity, its increase resulting in a significant an d progressive wider asymmetrical left shift (yellow) of the color hist ogram.