What causes sudden drop in heart rate?

I have a 37 year old male neighbor who started having dizzy spells and passing out a week ago.  He was taken to the hospital 3-4 days ago.  They have found that his "electrical part" of his heart is mis-firing or cross-firing or something like that.  It is causing his heart rate to drop down to 28-30 causing the spells.   They are planning on doing a pacemaker on monday.  They have done 2 MRIs on his heart.  The only irregularity they have found with any test is that the right side of his heart is thicker than normal.  The second MRI was done to get a better picture of the right side.  They still didn't get the picture they wanted so they have another one scheduled for Monday morning before they do the pacemaker.  The doctors are trying to determine if they need to put a defibrallator in, too.  That is the background.  My questions are:  What would cause this to suddenly start happening?  What could they be looking for on the MRI?  Is the procedure going to fix the problem or just the symptom?


This discussion is related to Sharp drop in heart rate.