Dual Chamber Pacing Aborts Vasovagal Syncope Induced by Head-Up 60° Tilt

To determine if pacing might prevent syncope in cardioinhibitory ‘Malignant Vasovagal Syndrome’ (also known as ‘Neurally-Mediated Bradycardia/Hypotension’), a study of dual chamber pacing during head-up 60° tilt was undertaken. Paired invasive tilts were performed in 10 patients who had a history of recurrent syncope, normal routine investigations including electrophysiological study and prior tilt induced vasovagal syncope. Vasovagal reactions of identical severity were produced by prolonged 60° head-up tilt on consecutive days in seven out of 10 patients. On day 2, without pacing, seven patients had tilt-induced vasovagal reactions and six became syncopal during the reaction. On day 3, with temporary DVI pacing with rate hysteresis, seven patients had tilt-induced vasovagal reactions and 1 patient was syncopal. Syncope was aborted in the other five patients. DVI pacing significantly improved cardiac index (CI) (one ± 0.2 to 1.6 ± 0.3 L/min/m², P < 0.01) and mean arterial blood pressure (MABP) (30 ± 11 to 48 ± 12 mmHg, P < 0.01) during vasovagal reactions on day 3 compared with day 2. The mean period of time that patients could tolerate in the tilted position after the onset of the tilt-induced vasovagal reaction was significantly prolonged by pacing from 0.9 ± 1.2 to 3.2 ± 1.6 min (P < 0.01). Dual chamber pacing may abort syncope in 85% of patients with cardioinhibitory malignant vasovagal syndrome. Pacing may prolong consciousness sufficiently during a vasovagal reaction to allow injury to be avoided.