What type of devices should a person with a pacemaker be cautious about? Cardiology Basics

What type of devices should a person with a pacemaker be cautious about? Cardiology Basics

Artificial pacemakers are cardiac implantable electronic devices (CIED) which give tiny electrical signals to the heart when the heart’s own pacemaker is not functioning well. Sinus node is the natural pacemaker of the heart, located in the upper part of right atrium near the orifice of superior vena cava.

Pacemakers may also be used when the impulses from the sinus node are not conducted well to the ventricles in complete atrioventricular block. Pacing for bradycardia can be with single chamber or dual chamber pacemakers, depending on the indication for pacing. Dual chamber pacemakers are AV sequential pacemakers which pace the atrium first and then the ventricle after a short programmable AV delay. Single chamber pacemaker can pace either the atrium or the ventricle, usually the right atrium or right ventricle.

Being an electronic device, which functions on an in build battery, pacemaker function can be interfered by strong electrical and magnetic signals in the vicinity. This is known as electromagnetic interference of pacemakers. Moreover, modern pacemakers communicate with the equipment used for programming them using radio waves. This communication can also be interfered with by strong electromagnetic fields.

The pacemaker has built in circuitry and a metallic shielding to reduce such interference. Still if the electromagnetic field is very strong, interference with function or communication can still occur.

In the earlier era, the most likely causes were electrical equipment and devices like speakers which have magnets within which used to be important sources of electromagnetic interference. Magnets can activate the reed switch in a pacemaker and shift the pacemaker to asynchronous pacing mode.

But now, probably the most common electromagnetic equipment which we use is a mobile phone. While using a mobile phone, keep it as far away from pacemaker site as possible, at least 15 cm, typically in the opposite ear. If pacemaker pulse generator has been implanted below the left clavicle, use the mobile phone in the right ear.

Of course, a person with a pacemaker should keep away from mobile towers as the signal strength there is very much higher than that from a phone. But this is not usually a problem as the towers are usually located high up.

Other important electromagnetic devices are metal detectors at airports and theft detectors at malls. An identity card will be needed at airports to avoid metal detectors.

In the hospital, there are several devices which can generate electromagnetic waves like surgical cautery, defibrillators, radiation therapy, dental instruments, nerve and muscle stimulators, which need special precautions. Using bipolar cautery and using cautery in intermittent short pulses can reduce the interference. Pacemaker can be programmed to operate continuously prior to the procedure. Reprogramming is done after the surgery. Another important precaution is to keep the indifferent electrode of the cautery as away from the pacing circuit as possible.

Most important equipment to be thought of in the hospital is an MRI scanner. With older generation pacemakers, MRI was prohibited. But with newer MRI conditional pacemakers, MRI scan if urgently needed, can be done with special precautions. MRI conditional pacemakers use special components and software to ensure safety in MR environment. They can automatically switch to MRI mode on reaching the MR console. Alternatively they can be programmed to that mode using a programming device prior to entry into the MR console.