title: Dual chamber pacing aborts vasovagal syncope induced by head-up 60 degrees tilt.
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 degrees 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 degrees 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 less than 0.01) and mean arterial blood pressure (MABP) (30 +/- 11 to 48 +/- 12 mmHg, P less than 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 less than 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.
authors.affiliation: Cardiac Department, Westminster Hospital, London, England.
authors.forename: A
authors.initials: A
authors.lastname: Fitzpatrick
authors.forename: G
authors.initials: G
authors.lastname: Theodorakis
authors.forename: R
authors.initials: R
authors.lastname: Ahmed
authors.forename: T
authors.initials: T
authors.lastname: Williams
authors.forename: R
authors.initials: R
authors.lastname: Sutton
mesh_terms: D000328:Adult; D000368:Aged; D001794:Blood Pressure / Q000502:physiology; D001919:Bradycardia / Q000517:prevention & control*; D002302:Cardiac Output / Q000502:physiology; D002304:Cardiac Pacing, Artificial / Q000379:methods*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007024:Hypotension, Orthostatic / Q000517:prevention & control*; D008297:Male; D008875:Middle Aged; D013318:Stroke Volume / Q000502:physiology; D013484:Supination; D013575:Syncope / Q000517:prevention & control*; D013577:Syndrome; D014630:Vagus Nerve / Q000503:physiopathology*; D014655:Vascular Resistance / Q000502:physiology