[914GT]

I cannot see a microwave oven interfere with a pacemaker unless the oven had a defective door seal causing to leak a lot of RF, and/or the pacemaker having some kind of wiring exiting the body. Otherwise the pacemaker, being deeply buried inside the body, is well protected from the microwave energy.

A follow-on comment .... I'd be more concerned with mobile phones or hand-held radios/transmitters and their interference potential to pacemakers. These can generate a few volts/meter field levels close to the body at frequencies that the human body does not shield well against. People worry about microwave ovens but don't hesitate to put an intentional radio transmitter right next to their brain.