Changes in left ventricular volume during head-up tilt in patients with vasovagal syncope: an echocardiographic study.

We tested the hypothesis that patients who have vasovagal syncope during head-up tilt have a greater decrease in their left ventricular volume in response to tilt than do normal subjects. Measurements were done in the supine position and during graded tilt by using two-dimensional echocardiography. We compared seven patients with vasovagal syncope with nine normal volunteers. The rate of reduction of end-diastolic volume index during tilt was faster in the vasovagal group than in normal subjects. A more significant reduction of stroke index and ejection fraction during tilt was found in the vasovagal group than in normal subjects, possibly because of more peripheral translocation of blood volume in the venous system during tilt and an early vagal effect on ventricular contraction.