For the answer to the question above, I believe that the answer to your question is that the heart rate will decrease if there's an extreme vagus nerve stimulation The vagus nerve is part of the parasympathetic nervous system. The sympathetic nervous system is the "fight or flight" part of the autonomic nervous system, whereas the parasympathetic is the "feed or breed" part. The sympathetic side acts to speed things up; it increases heart rate, the blood pressure, also the respiratory rate, it dilates pupils, shunts blood away from the GI tract, and so on...
The parasympathetic the opposite in which acts to slow things down; it lowers down the heart rate or decrease blood pressure, it increases salivation, increase blood flow to the GI tract, and so on. The two systems are always balancing each other. The confusing part is that when you INCREASE the activity of the parasympathetic nervous system you DECREASE the activity of the heart; so increased vagal tone will slow the heart rate, decreases the contractility, and lowers blood pressure. When the heart is excitable and has certain types of arrhythmia, increasing the vagal stimulation can slow the heart down enough to allow the normal pacemaker functions to take over again also called as converting.
