Diagram of traditional pacemaker and wire placements
One of the more common questions a patient has when using electrotherapy devices is whether it will interfere with their implanted demand cardiac pacemaker. The question is very reasonable due to the way a demand heart pacemaker works.
How A Demand Cardiac Pacemaker Works:
A heart demand pacemaker is an implanted device that uses a battery powered stimulator, connected to wires, and the wires are strategically placed to stimulate heart muscles. The pacemaker itself is also what is called a "biofeedback" type device because the pacemaker actually is monitoring the continuing electrical output of the heart muscles as they contract. The pacemaker detects the electrical charges emitted by the heart muscles when they pump, contract to move the blood.
If the demand pacemaker fails to discern electrical activity over a pre set time period then it is assumed the heart has stopped and an electrical stimulus is emitted by the battery, down the wires to the heart nerves to stimulate the heart to restart pumping blood. Many patients who have the pacemakers installed testify to feeling the surge of electrical energy at times to stimulate their heart. It is a life saving device.
The Danger Of A Tens Machine With A Demand Pacemaker:
The issue one has with electrical devices, such as tens units ( transcutaneous electrical nerve stimulators), is the tens unit is constantly emitting electrical messages/signals and those signals may interfere with the pacemaker sensing the lack of electrical stimulus by the heart muscles themselves. The tens unit electrical discharge will be going on and on so the pacemaker assumes those same electrical currents are coming from the heart and therefore does not stimulate the heart muscles and the patient dies.
The general rule is to not apply tens type electrodes in the chest area simply as a safeguard that effect will not happen. The tens machines, and many other devices customarily say "do not use if wearing a pacemaker". Now not all pacemakers are "demand" type however the vast preponderance are. The truth though is most tens units and many portable electrical devices simply do not have the electrical energy to penetrate and interfere with what the pacemaker is monitoring. Most tens devices hardly penetrate the skin, much less deep within body tissues and cavities.
Generally speaking if the electrodes are placed away from the chest area then most medical doctors do not worry about electrical interference and failure of the pacemaker to stimulate.
More Powerful Clinical Electrical Devices
Today we have portable devices that are used for the same reasons a tens unit is used and most of these devices are demonstrably better for the condition related than tens. One such electrotherapy device is the portable interferential device, Infrex Plus, the patient takes home for self treatment. Unlike a tens unit which goes off and on at most 150 times per second, the interferential device goes off and on 8,150 times per second. The output is significantly greater and the depth of penetration is also. Clinical interferential devices have been used since 1953 with patients and there has been no reported interferences with demand pacemakers I'm aware of. The essence of interferential is to have a high "rate" ( off and on) as this allows better penetration of the electrical charges to the actual areas where electrical energy is needed. The physics of this higher rate dictates the efficacy is derived from the ability to deliver electrical currents deeper into the tissues and toward the targets within the body.
The benefit of the interferential machine is the treatment time is measured in minutes so a patient can self treat for 20 - 60 minutes and that may be all that is necessary for 24 hours. Over time, and ability to self treat to prevent pain etc. , the use of an interferential device is not needed since the condition improves and fewer treatments are needed. This is contrasted to a tens machine which is worn continuously, sometimes 24 hours per day, and there is constant electrical energy versus the 20 - 60 minute time periods of interferential therapy. The constant output of a tens unit is considerably greater time than an interferential unit which provides carryover pain relief.
As with all medical devices one should follow the directions given. Always inform the treating physician if you have a demand type cardiac pacemaker before beginning treatments so you can be monitored. The benefits of short daily interferential sessions, once found successful in the clinic, may be warranted with a take home device, even when one wears a demand cardiac pacemaker. This is especially true if pain is being experienced in the legs, low back, scitica, neck, shoulders, feet and other areas away from the chest.