Subject: What happens when an EMP field intersects an EM field?

I was recently reading about a propsal to give police access to 'EMP Guns' for 
use in stalling the engines of vehicles, but one of the concerns about the idea 
was if the driver had a pacemaker...

From what I understand, regular EMP shielding (in the form of sheet metal,) 
would be entirely unsuitable. And, I think, the electrodes connected to the 
patient's heart would fire. 

Would it be possible to shield against an EMP by using a high powered 
electromagnetic field? (EG - do magnetic fields expend energy on each other 
when they intersect?) Also, if this were a high altitude detonation of a 
nuclear bomb, would the radiation responsible for causing the EMP negate this 
somehow?

Re: What happens when an EMP field intersects an EM field?