 Vasodilatation is an obligate element of all vasovagal syncopal episodes and in many also an early sign associated with the hyperkinetic empty left ventricle which triggers the reflex wave. The principle in closed loop stimulation CLS is a continuous surveillance of the impedance in the right ventricle which correlates highly with myocardial contractility. When contractility is increased significantly atrial pacing with prolonged AV delay is commenced. This principle has been used in chronotropic incompetent patients and in one small study of patients with vasovagal syncope with a positive outcome. The hypothesis is that the CLS will potentially identify an incipient vasovagal attack and be able to prevent the drop in cardiac output and bradycardia by early accelerated pacing. 