The main concern is electromagnetic interference (EMI) from electrocautery (especially monopolar), evoked potential monitors, nerve stimulator, external defibrillation, radiofrequency ablation, and extracorporeal shockwave lithotripsy. EMI can be interpreted as intrinsic cardiac signal. This can lead to inappropriate inhibition leading to pathologic bradycardia, or oversensing leading to pathologic tachycardia.
Electrocautery current can potentially pass through pacer leads to the pulse generator, interfering with the sensing and generation of pacer signal. It can also potentially cause damage to the endocardial tissue. According to the 2011 ASA practice advisory, the cautery tool and the return pad should be positioned in such a way to avoid passage of current through the pacer leads or the generator. It also recommends short intermittent and irregular bursts at the lowest possible energy. The use of bipolar rather monopolar cautery is thought to be safer in such patients.
There is a concern for R on T phenomenon, especially during lithotripsy. According to the 2011 ASA practice advisory, the atrial pacing should be disabled prior to the procedure.
Radiofrequency ablation when in proximity to the pacer leads can cause a significant drop in the resistance; therefore, the advisory recommends avoidance of direct contact between ablation catheter and pacer leads or the pulse generator.
Electroconvulsive therapy (ECT) can lead to transient electrocardiographic changes, such as increased P-wave amplitude, altered QRS shape, T-wave and ST abnormalities. Thus the advisory recommends comprehensive interrogation of the pacer/AICD prior and after ECT, with ICD function disabled for shock therapy. It is recommended that the care team make preparation for treatment of ventricular dysrhythmias caused by the hemodynamic changes of ECT. Patient may require a temporary pacing system during the shock therapy, or have the pacer/AICD programmed to asynchronous mode to avoid myopotential inhibition.
During emergency defibrillation or cardioversion, the current can flow through the pulse generator and lead system. Therefore, the advisory recommends positioning the defibrillation or cardioversion pads or paddles as far away as possible from the pulse generator.
References
- Apfelbaum, JL et al. Practice Advisory for the Perioperative Management of Patients with Cardiac Implantable Electronic Devices: Pacemakers and Implantable Cardioverter-Defibrillators: An Updated Report by the American Society of Anesthesiologists Task Force on Perioperative Management of Patients with Cardiac Implantable Electronic Devices. Anesthesiology Issue: Volume 114(2), February 2011, pp 247-261 Link
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