Vertical left ventricular angulation assessed by thallium 201 myocardial perfusion imaging in patients with mitral valve prolapse.

Mitral valve prolapse has been associated with septal to aortic root angle abnormalities determined by echocardiography. Thallium 201 imaging in the anterior view permits visualization of the left ventricular long axis. In the present study, the vertical angle was defined as the angle formed by the long axis of the left ventricle and a horizontal line. The vertical angle was determined in 25 patients who had 201 TL stress testing and M-mode echocardiography. Group I (11 patients) had mitral valve prolapse and group II (14 patients) did not have mitral valve prolapse. The vertical angle and ultrasound were read blinded to each other. Height, weight, and body surface area were compared for the two groups, and receiver operator curve analysis performed. Vertical angle measured by TL 201 was significantly more vertical in patients with mitral valve prolapse. Receiver operator curve analysis showed that an angle of greater than 30 degrees successfully identified 9/11 patients with mitral valve prolapse, with a sensitivity of 82% and a specificity of 79%. There were no significant differences in height, weight, or body surface area between the two groups. Thus, patients with mitral valve prolapse have more vertically positioned hearts than patients without mitral valve prolapse, independent of body habitus. The different appearance of a vertically oriented heart may contribute to false-positive readings of TL 201 images.