Although several studies have examined the safety of cellular phone use in patients with pacemakers, the impact of digital cellular telephones on implantable cardioverter-defibrillators (ICDs) has been less studied. Electromagnetic fields may interfere with an ICD, causing inappropriate sensing or temporary suspension of arrhythmia detection. This investigation evaluated the effect of digital cellular telephone use on ICD function in patients and in vitro.
A group of 41 patients with ICDs (manufactured by Medtronic, Inc.) performed a series of tests using a digital cellular telephone (AT&T model 6650 with NADC/TDMA-50 technology). Patients were connected to an electrocardiogram monitor and continuously observed while they received and transmitted calls at both the right and left ears; moving the entire route of the lead from electrode in the heart to its connector end; and on top of the implantation site (to simulate carrying the telephone in the upper shirt pocket or at the belt). The effect of increasing the electromagnetic field intensity was analyzed in vitro by suspending an ICD in a saline bath and observing the field required for the ICD to sense electromagnetic interference.
For the tests conducted on patients, no ventricular tachycardia or fibrillation was activated by the electromagnetic interference in any patient. There was no evidence of pacing inhibition or changes to the programmed pacing intervals during any test. The in vitro tests indicated no interaction between the digital phone and ICD function during normal operation. However, the static magnetic field generated by the cellular phone placed over the ICD at a distance of 0.5 cm or less can activate the internal reed switch, which would result in temporary suspension of ventricular tachycardia and fibrillation detection.
The investigators concluded that the TDMA-50 cellular telephones did not interfere with the types of ICDs examined in this study. However, based on the results of the in vitro tests, they recommended the following:
1. maintaining a minimal separation of 15 cm (6 inches) between a 0.6W cellular phone and antenna to the implanted device, and 30 cm (12 inches) for telephones with 3W or more of power;
2. holding the telephone on the ear opposite the side of the implanted device;
3. not holding the telephone near the chest while dialing or conversing, nor carrying the telephone in a breast pocket or on a belt within 15 cm of the implanted device (whether or not it is in use); and
4. storing the telephone in a location opposite the side of the implanted device.
A group of 41 patients with ICDs (manufactured by Medtronic, Inc.) performed a series of tests using a digital cellular telephone (AT&T model 6650 with NADC/TDMA-50 technology). Patients were connected to an electrocardiogram monitor and continuously observed while they received and transmitted calls at both the right and left ears; moving the entire route of the lead from electrode in the heart to its connector end; and on top of the implantation site (to simulate carrying the telephone in the upper shirt pocket or at the belt). The effect of increasing the electromagnetic field intensity was analyzed in vitro by suspending an ICD in a saline bath and observing the field required for the ICD to sense electromagnetic interference.
For the tests conducted on patients, no ventricular tachycardia or fibrillation was activated by the electromagnetic interference in any patient. There was no evidence of pacing inhibition or changes to the programmed pacing intervals during any test. The in vitro tests indicated no interaction between the digital phone and ICD function during normal operation. However, the static magnetic field generated by the cellular phone placed over the ICD at a distance of 0.5 cm or less can activate the internal reed switch, which would result in temporary suspension of ventricular tachycardia and fibrillation detection.
The investigators concluded that the TDMA-50 cellular telephones did not interfere with the types of ICDs examined in this study. However, based on the results of the in vitro tests, they recommended the following:
1. maintaining a minimal separation of 15 cm (6 inches) between a 0.6W cellular phone and antenna to the implanted device, and 30 cm (12 inches) for telephones with 3W or more of power;
2. holding the telephone on the ear opposite the side of the implanted device;
3. not holding the telephone near the chest while dialing or conversing, nor carrying the telephone in a breast pocket or on a belt within 15 cm of the implanted device (whether or not it is in use); and
4. storing the telephone in a location opposite the side of the implanted device.
Digital Cellular Telephone Interaction With Implantable Cardioverter-Defibrillators
Authors: Fetter, JG, et al
Source: Journal of the American College of Cardiology
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