Scott, included in peripheral nerves is the autonomic nervous system which is out side our conscious control. It deals with dilatation and constriction of blood vessels, hence blood pressure, the speeding up and slowing down of the heart beat, the movement of the guts, the spasm or opening of the bronchial tubes etc. All these can also be affected by humoral control, that is adrenalin from the adrenal glands in turn controlled by the pituitary gland in the brain.
There is within the heart an electrical conduction system for bringing impulses to the atria and the ventricles via the bundles of Hiss. Certain atrial tissue can develop its own pacemaker hence atrial fibrillation at upto 300 beats per minute .
If there is block to conduction the ventricles settle down to their own intrinsic rate of less than 40 b.p.m., this is typically the circumstances where a pacemaker is needed.
GBS can involve the autonomic nervous system so many have widely variable blood pressures and heart beat rates. If there is no heart block I would hesitate about a pacemaker unless circulation to brain or cardiac tissue is being impaired, by an excessively rapid rate. DocDavid