Occasionally permanent pacemaker implantation is necessary - generally when tilt table testing elicits prolonged cardiac standstill. 

The vast majority of scientific trials looking at the effectiveness of cardiac pacing as a treatment for neurocardiogenic syncope have not been placebo controlled. However, one  recent trial - Second Vasovagal Pacemaker Study (VPS II 2003) was double-blinded and showed no benefit  from pacing once the placebo effect was removed. 

Unfortunately this trial did not look specifically at the group most likely to benefit from pacing - those with significant cardiac standstill on provoked syncope. 

This picture shows a typical top-of-the-range pacemaker used to treat Carotid Sinus Syndrome. 

This image is reproduced with kind permission from Medtronic.