Some new pacemakers are [MRI compatible][1] ([[1]]). Of those, some have an exclusion zone where the body may not be scanned. I wouldn't be surprised if, in a few years, all new pacemakers and ICDs will be MRI compatible. Older pacemakers still won't be, however. The following quote from [[1]], lists problems MRI fields may present cause with pacemakers:

 * Heating at the lead tip and at the lead tissue interface • Force and torque on devices
 * Image distortion
 * Alteration of programming with potential damage to
the pacemaker circuitry
 * Rapid atrial pacing
 * Pacing at multiples of the radiofrequency pulse and
associated rapid ventricular pacing • Reed switch malfunction
 * Asynchronous pacing
 * Inhibition of pacing output
 * Induction of ventricular fibrillation
 * Electrical reset
 * Component damage
 * Death

To be certified as compatible by the FDA, TÜV, etc. as MRI compatible, each pacemaker system (device and leads) must be tested for MRI compatibility but the manufacturer.

In the interest of full disclosure, I work for one of the one of the device manufacturers listed in the paper[[1]].

  [1]: http://dx.doi.org/10.1111/pace.12061