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

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Abstract
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.