Pacemakers, defibrillators and Mohs: the five facts your surgeon actually needs

The intake form asks whether you have a pacemaker. You tick yes. That is usually where the conversation ends until the day of the procedure, when someone in the surgical suite realizes that nobody knows whether the device is a pacemaker or a defibrillator, whether you are dependent on it, or who to call, and a case that should have taken four hours acquires a phone tree.

This is one of the few situations in dermatologic surgery where a patient can materially improve the safety and the smoothness of their own procedure with about twenty minutes of preparation, and where nobody tells them what to prepare.

The original element in this piece is a disclosure card built from the five specific facts a Mohs team needs about an implanted cardiac device, stating where each one is found, what each one changes about the procedure, and the two of the five that are worth confirming with your cardiology office rather than reading off a card. Guidance on electrosurgery near cardiac devices exists in abundance for clinicians. None of it is addressed to the person who owns the device, which is why the information usually arrives late, incomplete and secondhand.

What the actual risk is. Nearly every Mohs case involves electrosurgery, the handheld unit used to seal small bleeding vessels between stages and during the repair. It works by delivering high frequency current into tissue. An implanted cardiac device is a sensing machine, and current in nearby tissue can be misread as cardiac electrical activity. The two consequences that matter are that a pacemaker may be inhibited, meaning it withholds a beat it should have delivered, or that a defibrillator may interpret the interference as a dangerous rhythm and deliver a shock to a patient who does not need one.

The reassuring part is what the field's own data shows. Surveys of cutaneous surgeons' experience with electrosurgery in patients with pacemakers and defibrillators found reported complications to be rare, and the underlying work on dermatologic electrosurgery in device patients has generally supported that with sensible precautions these cases proceed uneventfully. More recent bench work looking specifically at hyfrecation and interference with implantable cardiac devices has helped refine which settings and configurations actually generate detectable interference. The risk is small. It is not zero, and the difference between small and zero is preparation.

Fact one, device type. Pacemaker or implantable cardioverter defibrillator, and if it is a defibrillator, whether it also paces. These are different devices with different failure modes and the precautions differ. It is written on the identification card you were issued at implant, and it is the single most important line on that card. Bring the card.

Fact two, manufacturer and model. Also on the card. This matters because if the team decides to have the device interrogated or reprogrammed around the procedure, the representative who does that is manufacturer specific, and knowing the brand at the time of booking rather than on the morning is the difference between an arranged visit and a scramble.

Fact three, whether you are pacing dependent. This is the one that most changes the plan, and it is the one patients almost never know. Pacing dependent means your own underlying rhythm is inadequate and the device is producing most or all of your heartbeats. A brief inhibition in a non dependent patient is a non event. In a dependent patient it is not. This is not on the card. Call your cardiology office and ask them the question in exactly those words: am I pacing dependent.

Fact four, when the device was last interrogated, and its battery status. Also from cardiology. A device checked six weeks ago with a healthy battery is a very different proposition from one that has not been interrogated in two years. If the team wants a check before the procedure, knowing this early gives everyone time to arrange it.

Fact five, the location of the generator. The metal box, usually under the skin below one collarbone. This matters because the practical precautions all revolve around distance and current path. A Mohs case on the lower leg is a different situation from one on the temple or the ear on the same side as the device. You can feel where it is. Say which side.

What changes with each answer. A defibrillator in a patient having work on the head or neck is the combination most likely to prompt a plan involving either temporary deactivation of shock therapies with monitoring, or a magnet on standby, or a manufacturer representative in the building. Pacing dependence usually prompts asymmetric caution about how the electrosurgical unit is used and where the return path lies. A device on the same side as the surgical site tightens all of the above. Many teams will simply favor short controlled bursts, alternative hemostasis where practical, and careful positioning of any grounding pad so that current never crosses the chest. None of this is dramatic and most of it is invisible to you, which is exactly why it needs to be arranged before rather than during.

How to deliver it. Write the five facts on one card or one phone note, and hand it over at the visit where the procedure is booked rather than on the day. That timing is the entire value of the exercise. A team that learns on Tuesday that you have a defibrillator and are pacing dependent can arrange whatever it needs before Friday. A team that learns it on Friday morning either delays you or proceeds with less information than it would have liked. It belongs alongside the rest of preparing for your procedure and it fits naturally into the questions worth bringing to the consultation.

One thing not to do. Do not stop any cardiac medication in anticipation of the procedure unless the prescriber tells you to. This gets tangled up with the separate and much more common question of what to hold, and the default in dermatologic surgery for medically necessary drugs is to keep them running. Whatever the device conversation concludes, it is not a reason to alter medication on your own initiative.

What the studies do not tell you. The published evidence here consists of surveys, bench experiments and case reports. There is no randomized trial of electrosurgery in device patients, because there could not ethically be one, which means every recommendation in this area is built from mechanism and accumulated experience rather than from controlled comparison. The reported complication rate is low, but reported is doing real work in that sentence, since a brief inhibited beat under drapes is not something anybody would necessarily notice or record. The honest summary is that this is a low probability, high consequence interaction, and preparation is cheap.

Five facts, one card, handed over at booking. It is the least glamorous contribution a patient can make to their own procedure and one of the few that measurably helps.