Reflexes & Pathologies including the Vagus Nerve
One pathology affecting the vagus nerve is autonomic neuropathy which can be secondary to several causes-one of the most commonly acquired cause is diabetes mellitus. It can manifest with various symptoms such as resting tachycardia (heart beating fast without exercise), exercise intolerance, orthostatic hypotension, constipation, gastroparesis (delayed gastric emptying), etc. 

If you'd like to read more-http://care.diabetesjournals.org/content/26/5/1553.full

Hope its helpful.