Vasovagal Syncope International Study - VASIS


Vasovagal Syncope International Study (VASIS) was a small randomized trial comparing dual-chamber pacemaker implantation versus no pacemaker for the treatment of vasovagal syncope in patients with cardioinhibitory (bradycardic) responses to tilt table testing.


Dual chamber (DDI mode) pacing with rate hysteresis will reduce the risk of recurrent syncope compared with not implanting a pacemaker.

Study Design

Study Design:

Patients Screened: ≈1,200
Patients Enrolled: 42
Mean Follow Up: 3.7 ± 2.2 years
Mean Patient Age: Mean: 64 years (pacer), 56 years (no pacer)
Female: 43

Patient Populations:

1) Vasovagal syncope with ≥3 episodes in two years.
2) Most recent syncope within six months of study entry.
3) Age >40 or documented failure of conventional drug therapy if age <40.
4) Cardioinhibitory response on tilt table testing, defined as ventricular rate <40 bpm for >10 seconds or asystole for >3 seconds, with hypotension.


1) Other cause of syncope known or suspected.
2) Myocardial infarction within six months.
3) New York Heart Association class III or IV heart failure.
4) Severe comorbid disease.

Primary Endpoints:

Recurrent syncope

Secondary Endpoints:

Response to repeat tilt table testing following initial treatment assignment

Drug/Procedures Used:

Patients were randomized to dual-chamber pacemaker implantation or no pacemaker implantation. All pacemakers were programmed to the DDI mode at 80 bpm, with an AV interval of 150 ms and a rate hysteresis of 45 bpm.

Concomitant Medications:

No other specific medical therapies for syncope were permitted in the trial. Investigators discouraged changes in any other vasoactive therapies (e.g., antihypertensive medicines).

Principal Findings:

Recurrent syncope occurred in 1/19 patients (5%) in the pacemaker group versus 14/23 (61%) in the no pacemaker group, p=0.0006. The median time to first recurrent syncope in the no pacemaker group was five months. This effect occurred despite a lack of change on repeat tilt table testing within 15 days after enrollment (tilt positive 59% with pacemaker, 61% without, p=NS).


Dual chamber pacemakers appear to reduce the frequency of recurrent syncope in highly selected patients with frequent vasovagal syncope and cardioinhibitory responses to tilt table testing. The authors caution that a placebo effect from pacemaker implantation could not be excluded—an effect that appeared to be present in the larger North American Vasovagal Pacemaker Study II.


Sutton R, Brignole M, Menozzi C, et al. Dual-chamber pacing in the treatment of neurally mediated tilt-positive cardioinhibitory syncope: pacemaker versus no therapy: a multicenter randomized study. The Vasovagal Syncope International Study (VASIS) Investigators. Circulation 2000;102:294-9.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, SCD/Ventricular Arrhythmias

Keywords: Syncope, Vasovagal, Placebo Effect, Tilt-Table Test, Hypotension, Pacemaker, Artificial, Heart Arrest, Bradycardia

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