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An electromagnetic therapy for depression shouldn't damage a person's pre-existing implantable cardioverter-defibrillator (ICD), multiple experiments indicated.

There was a low risk of ICD damage or overheating during transcranial magnetic stimulation (TMS), used to treat various neuropsychiatric disorders, even when stimulation was much stronger than normal, reported Felix Wegner, MD, of University Hospital Muenster, Germany, and colleagues in .

Researchers had several Biotronik ICDs hooked up to an arrhythmia simulator and exposed ex vivo to magnetic stimulation, using MagStim equipment, with an increasing gradient during continuous device telemetry:

• Biotronik Itrevia 7 VR-T Dx ICD programmed in a single-chamber mode: No signal interference detected up to an output of 50% of maximum. At the maximum possible output, intermittent ventricular oversensing of the stimulation impulse occurred. No significant changes in lead impedance, sensing amplitude, or thresholds were observed.
• Biotronik Intica Neo 7 DR-T ICD programmed to a dual-chamber mode: Atrial oversensing occurred at an output of 25% of maximum, leading to a pacemaker tachycardia which was correctly identified and terminated by the device. No significant changes in lead impedance, sensing amplitude, or thresholds were observed.
• Biotronik Intica Neo 7 DR-T ICD programmed to the device's MRI mode and asynchronous pacing (DOO 80/min): No interaction between magnetic stimulation and the device even at the maximum output. No significant changes in lead impedance, sensing amplitude, or thresholds were observed.

Finally, a last experiment showed that a Biotronik Rivacor 5 VR-T Dx ICD, connected to a Medtronic Sprint Quattro Secure MRI SureScan 6947M dual-coil defibrillator lead and immersed in saline solution, stayed undamaged when it was programmed to a single-chamber mode and exposed to magnetic stimulation at an output of 70% of maximum and a repetition rate of 0.9 Hz for 15 minutes. The temperature of the saline bath did not change, either.

"In summary, our proof-of-principle experiments indicate that the risk of damage to an ICD and heating of an ICD may be low during magnetic stimulation, even when stimulation is delivered directly to the device. We consistently used a far greater output at a far closer distance to the ICD than would be realistic for TMS/TCMS [transcutaneous magnetic stimulation]," Wegner's group wrote.

"In light of the high comorbidity of depression in cardiovascular disease and its distinct effect on outcomes and prognosis, this might add therapeutic options for a significant proportion of cardiac patients," the authors suggested.

There is evidence that depressive symptoms are associated with a higher risk for all-cause and cardiovascular disease mortality, though causation is not proven.

TMS is FDA-approved for a range of psychiatric and neurologic disorders, including depression and obsessive-compulsive disorder. Sessions comprise brief electrical currents delivered through a coiled wire placed on the scalp. Cortical neurons at varying distances below the scalp may be activated, depending on the stimulation intensity.

Recently, a similar technique, TCMS of the left stellate ganglion, was shown to be a .

"Importantly, TMS/TCMS uses temporal gradients of magnetic field exponentially higher than magnetic resonance imaging," study authors noted.

They cited concerns that direct interference between magnetic stimulation and an ICD can lead to permanent damage to the circuitry of the ICD, heating of the ICD, and oversensing of the magnetic impulses leading to inhibition of pacemaker stimulation or inappropriate defibrillation.

"Because only Biotronik ICD and Medtronic defibrillator leads were studied, research on ICD, pacemakers, and magnetic stimulation coils and generators of all types and manufacturers in more physiologic models of magnetic device interference is warranted," Wegner and colleagues observed.

"However, our data could encourage investigators using TMS/TCMS to include device patients in future studies after careful individual risk/benefit analysis," they continued.

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