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Electromagnetic Interference: A Case Report Illustrating the Hazards of Electromagnetic Fields in Swimming Pools
Introduction
Electromagnetic interference (EMI) is known to cause potentially dangerous interactions with cardiovascular implantable electronic devices (CIED). Upon implantation, patients are educated on avoidance of sources of strong EMI. Historically, EMI sources inside and outside the home, such as metal detectors, microwave ovens, running engines, high-power voltage, radar or magnet sources, and electric arc welding, have been prioritized for patient education. More recently, induction cooktops and cellphones with magnetic features have been reported to pose EMI problems to individuals with a CIED.
In the health care setting, external EMI sources can include electrocautery, radiofrequency ablation, cardioversion and defibrillation, lithotripsy, diathermy, electroconvulsive therapy, transcutaneous electrical nerve stimulators, and certain dental equipment, as well as radiation therapy and magnetic resonance imaging.
The potential impact of EMI on CIEDs is dependent upon the distance the CIED is from the EMI source, the presence and degree of shielding, programmed sensing polarity, lead design, and the CIED’s ability to filter certain EMI signals. Recent generations of CIEDs are designed with specific features to protect the CIED against EMI.
CIEDs affected by EMI may demonstrate oversensing interference on the atrial and/or ventricular lead. On the atrial channel, oversensing of the EMI may lead to atrial pacing inhibition, inappropriate mode switching, or in the case of a mode switch feature not being programmed on, triggered ventricular pacing at the programmed upper rate limit.
Ventricular pacing inhibition may also result from EMI-induced oversensing by the ventricular lead. This is particularly worrisome in pacemaker-dependent patients. The risk of EMI on the ventricular channel is greater in implantable cardioverter-defibrillator (ICD) patients as they may not only experience pacing inhibition, but also inappropriate arrhythmia detections and subsequent inappropriate therapies.1
In addition to those commonly known EMI hazards, clinicians who work with CIED patients have encountered patients who have demonstrated exposure to EMI around swimming pools. Unsuspecting CIED patients are vulnerable to these unanticipated environmental dangers involving the combination of water and electricity.
The following case presents an instance of EMI-mediated inappropriate ventricular fibrillation (VF) detection in a cardiac resynchronization therapy defibrillator (CRT-D) related to unrecognized electromagnetic field (EMF) in a swimming pool.
Case Presentation
The patient is a 58-year-old with a history of cardiomyopathy and chronic systolic heart failure. A CRT-D was implanted on March 2, 2017. Atrial and ventricular sensing polarities are programmed bipolar. Right ventricular (RV) lead noise and T wave discriminators are programmed on. Recent device interrogations show normal device function with appropriate pacing and sensing thresholds and lead impedance values.
In September 2020, the patient reported device tones after working with a “faulty pool pump.” No further information about that episode is available.
On June 1, 2022, the patient’s ICD device triggered a Bluetooth “alert” transmission to PaceMate. PaceMate’s proprietary alerts-based rules engine automatically triaged and prioritized the alert for prompt review by the device specialist for “Treated VF.” A review of the interval plot for the episode reveals a ventricular rate of 500 beats per minute (bpm) and atrial rate of 600 bpm.
The episode electrogram demonstrates a sine-wave pattern on both the atrial and ventricular channels with a rapid rate consistent with 60 Hz alternating current, a classic EMI pattern. Atrial pacing is demonstrated but ventricular pacing is inhibited, and no intrinsic ventricular activity is seen. The ICD detected the episode as VF and charged. However, the shock was withheld and aborted due to failure to reconfirm the rhythm.
Discussion
The patient is employed as a pool service technician and was servicing a pool at the time of the EMI episode. A pump in the pool was being used to drain the pool. The patient reported that he placed his hand into the pool and passed out. He did not require resuscitation and was transported to the emergency department for evaluation of syncope and possible aspiration of the pool water.
While not overly common, pool-related EMI incidents have been reported anecdotally and in the literature. The root cause of EMI in a swimming pool can come from various sources. One patient was shocked when he touched a handrail to exit the pool. An engineering assessment of the pool discovered high leakage currents coming from an area near the handrail, where a grounding connection was placed.2 There have been several reports of patients experiencing ICD shocks while sitting or swimming in a pool. Several reported events are attributable to alternating current leaks creating an EMF within the pool itself. Pool lighting and saline chlorination units are sources that have been reported more recently.3-5
A 2019 case report presented a 41-year-old patient who experienced 2 separate instances of inappropriate shock (1 year apart) while swimming in 2 different pools that each used a saline chlorination system. The replication of the first event in a second, different saline-chlorinated pool lends support to causality.6 Another patient received a shock from his subcutaneous implantable cardioverter-defibrillator (S-ICD) while touching the handle on a pool slide. Follow-up investigation revealed that an EMF was produced by a pool slide water pump that was located proximal to the metal handrail, which the patient was touching when he was shocked.
Conclusion
Improper grounding of or insufficiently insulated electrical systems in swimming pools can result in sufficient alternating current to generate an electromagnetic field. In the case under consideration in this report, exposure to this field resulted in EMI to the CRT-D. Consequently, this patient experienced inappropriate oversensing of the atrial and ventricular channels, inappropriate arrhythmia detection, and inhibition of pacing.
Electromagnetic fields in swimming pools are a potential environmental hazard to patients with CIEDs. For those individuals who have swimming pools, proper electrical insulation and grounding should be confirmed to avoid unnecessary risks. Pool and pool-equipment manufacturers and service companies should be made aware of the potential risks of electrical current leakage to patients and create engineering measures to mitigate these risks. The presence of sine waves or 60-Hz alternating current patterns, along with a collaborating history of a presence in or proximity to a swimming pool, should raise suspicion of a water source with electrical current leakage.
Additionally, CIED clinicians need to be aware of pools as an EMI source, and education of patients should include potential risks.2 PaceMate supports clinicians with patient education—offering the only software+service remote patient monitoring model with a communication team, and providing daily, ongoing patient education to improve monitor connectivity, patient compliance, and patient safety.
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This article is published with support from PaceMate and The Christ Hospital Health Network.
References
1. Driessen S, Napp A, Schmiedchen K, Kraus T, Stunder D. Electromagnetic interference in cardiac electronic implants caused by novel electrical appliances emitting electromagnetic fields in the intermediate frequency range: a systematic review. EP Europace. 2019;21(2):219-229. doi:10.1093/europace/euy155
2. Alzand BS, Leemput N, Willems R. Inappropriate implantable cardioverter-defibrillator shocks in a public swimming pool. EP Europace. 2014;16(8):1124. doi:10.1093/europace/eut344
3. Chan NY, Wai-Ling Ho L. Inappropriate implantable cardioverter–defibrillator shock due to external alternating current leak: report of two cases. EP Europace. 2005;7(2):193-196. doi:10.1016/j.eupc.2004.09.010
4. Iskandar S, Lavu M, Atoui M, Lakkireddy D. Electromagnetic interference in a private swimming pool: case report. Indian Pacing Electrophysiol J. 2015;15(6):293-295. doi:10.1016/j.ipej.2016.02.008
5. Roberto ES, Aung TT, Hassan A, Wase A. Electromagnetic interference from swimming pool generator current causing inappropriate ICD discharges. Case Rep Cardiol. 2017;2017:6714307. doi:10.1155/2017/6714307
6. Wight J, Lloyd MS. Swimming pool saline chlorination units and implantable cardiac devices: source for potentially fatal electromagnetic interference. HeartRhythm Case Rep. 2019;5(5):260-261. doi:10.1016/j.hrcr.2019.01.011
7. Fastenrath FP, Kuschyk J, Borggrefe M, Akin I, Rudic B. A shocking experience: inappropriate subcutaneous implantable cardioverter-defibrillator shock at a public swimming pool. EP Europace. 2018;20(12):2020. doi:10.1093/europace/euy209
