Assessment of regional wall motion of the hypertrophic heart by phase analysis of thallium-201 images

Combined technique with gated planner thallium (Tl)-201 images and gated cardiac pool images were applied to evaluate cardiac hypertrophy and regional wall motion for 13 persons. These subjects consisted of four normal persons, four patients with hypertrophic obstructive cardiomyopathy (HOCM) and five patients with asymmetrical apical hypertrophy (AAH). The Tl-201 image and cardiac pool image were obtained using the gated technique, in which the R-R interval was divided into 16 parts, in the 30 deg left anterior oblique projection. The region of interest (ROI) in the left ventricle was defined by the threshold method and radially divided into 16 segments in the center of the left ventricular area. The count ratio, considered as an indicator of regional myocardial contractility, was calculated using the formula (EDc-ESc/EDc) in each ROI. The functional image and histogram, an indicators of the synchronization of left ventricular wall motion, were constructed by the fluctuation of the phase distribution in volume curves of Tl-201. These indicators were evaluated for the normals and the two groups of patients. The count ratio indicated a higher value in the region of the left ventricular free wall and the cardiac apex in the normals, HOCM and AAH. The count ratio at the septal region indicated a lower value in HOCM, in spite of marked septal hypertrophy. A significant fluctuation of the phase distribution was demonstrated in the septal region in HOCM, and also at the apical region in AAH. These findings suggested that the contractile mode of the hypertrophic heart had an abnormal spatial torsion in spite of the higher value of the left ventricular ejection fraction. We concluded that phase analysis of Tl-201 images is a useful means for assessing regional wall motion and the pathophysiology of the hypertrophic heart. (author)