What can cause a pulsating throbbing in your head and your pulse to drop if you have a pacemaker?

Migraine which are a very painful phenomenon, closely appearing like pulsating and excruciating headaches. The pulsing feature, is most commonly associated with extreme vasodilation of the vessels of the base of the brain. Hypertension also can feel like such.

Normally the only way to have your pulse drop with a cardiac pacemaker is to have it malfunction. Cardiac pacemakers i designed to give a continuous beat for the heart, which stops your pulse from dropping, while your brain can handle an increasing pulse. The only true way you can end up with no pulse is to go through Cardiac Arrest. 

More than 600. i'm just guessing