Dear Mort,
The electrical fields generated by computers is not enough to have any effect on pacemakers or ICDs. Generally the field must be the intensity of that generated by a large power generator or Arc welding to have an effect. Digital cell phones can be used but it is recommended that they not be placed directly over the device. And finally to clear up a common myth, microwaves are safe for pacemaker and ICD patients to use also.
Thank you.. The question has also risen regarding magnetic field where the "GOSS Rating" may be a factor