Cardiac pacemaker activity is subject to interference from a variety of electrical and radiofrequency fields. As new and more sensitive types of pacemakers are developed, the interference problem becomes more complex. Some potential sources of interference for implanted pacemaker systems include1 radio frequency (RF) transmission such as radio and television broadcasting; RF energy from miscellaneous sources such as microwave ovens and radar; carrier current on power transmission lines; magnetic fields around power transformers and conductors carrying electric current; and arcing and sparking electrical equipment such as power tools, commutator motors, and ignition systems of aircraft, automobile, motorcycle, and lawnmowers. Medical equipment, such as diathermy, electrocautery, neurosurgical stimulators, and high-voltage radiation therapy units, are common sources of electrical interference within the hospital.
The fixed-rate (asynchronous) pacemaker has a lowfrequency oscillator designed to deliver pulses at a desired cardiac stimulation rate. Once implanted, such units are fairly insensitive to electrical interference,