Creating Features to Improve Functionality in Medical Devices
If you are not in the medical device industry, you may be surprised to learn that the term electrodes does not just refer to the ones Metal Cutting Corporation makes for resistance spot welding and die sinker EDM.
In fact, medical electrodes are crucial components of cardiac pacing, cardiac defibrillation, and neurostimulation systems. And these electrodes, which are typically made from MP35N®, often depend on precision CNC Swiss-style machining for important features.
Components of Devices Using Medical Electrodes
In general, medical electrodes are designed to come into contact with body tissue and deliver an electrical signal to the treatment area via a catheter or similar device. These signal delivery systems — whether for pacing, defibrillation, or neurostimulation — have three main components:
- The pulse generator, which creates the electrical signal
- The lead, which is made from series of wires, coils, or cables, and carries the signal to the electrode
- The electrode, which is usually assembled towards the end of the lead and delivers the signal to the tissue
Most electrodes are in the form of rings cut from tubing. The tubing is made from an implant grade material such as MP35N, which is often used for its electrical properties as well as its other characteristics. (See more below.)
As an abrasive cutoff company, Metal Cutting is often called upon to cut tubing that is used for the purposes of ring electrodes in these medical devices. But sometimes that tubing needs something more — namely, features that require another of our capabilities, precision CNC Swiss machining.
Swiss Machined Features for Medical Electrodes
From the lead to the proximal distal end and along the length, these medical devices can have tubular components that are machined. In addition, the electrodes themselves can be machined to produce:
- Features that allow the electrodes to attach to the catheter
- Shaped surfaces to accomplish the necessary signal delivery task
- Other features that are unique to a particular device’s design and manufacturer
A Swiss-style lathe can yield machined tubular parts that have features like chamfers at the end, different diameters such as tapers at the end, and cross-holes. At the distal end, there can also be a tubular part, a machined solid part, or a coiled part over a machined part, all designed to optimize the delivery of the signal to the tissue that is being treated.
For example, one common electrode is what is referred to as a tip coil — essentially, a lead that has a coiled corkscrew tip at the end so that the electrode can attach to the tissue. Swiss machining allows for this type of coil or other barbed tip that can be pressed or screwed into tissue and resists being pulled out.
Applications for Medical Electrodes
The main applications for medical electrodes made from MP35N are:
- Pacemakers, which send an electrical pulse to keep the heart beating at the proper rate
- Implantable cardioverter defibrillators (ICDs), which shock the heart tissue to “reset” it and correct the heart rate
- Neurostimulation devices, which deliver a signal to nerves, usually for purposes of pain management
How are pacing and defibrillation systems used?
Pacemakers and ICDs are both small devices that are implanted under the skin. The devices contain a tiny computer to track the heart rate and rhythm, determining when and how to correct heart rate problems known as arrhythmias:
- Bradycardia, which is when the heart beats too slowly — less than 60 beats per minute
- Tachycardia, when the heart beats too quickly — more than 100 beats per minute
- Tachy-brady syndrome, when the heart rate is irregular and fluctuates between too fast and too slow — a condition often seen in people diagnosed with atrial fibrillation
There are some small differences between pacing and defibrillation systems. When a pacemaker senses that the heartbeat is out of rhythm, the device sends out electrical pulses to speed up or slow down and steady the heart rate.
When an ICD detects that the heart is beating far too fast or too erratically, the device sends out a shock to get the heart back into rhythm. However, some ICDs also function as pacemakers, sending out a signal when the heart rate is too slow.
When are pacemakers and ICDs needed?
Pacing systems might be needed when other treatments have not worked or with beta blockers or other heart medications that can slow down the heart rate. A pacemaker might also be needed in patients who have had a cardiac ablation procedure.
This is where tiny areas of heart tissue are cauterized to stop the heart’s natural pacemaker, the atrioventricular (AV) node, from sending out abnormal electrical impulses. However, the procedure can sometimes damage the AV node, requiring a pacemaker for heart regulation.
(Ablation can be performed on other tissue and, interestingly, also uses medical electrodes. However, ablation procedures are minimally invasive and do not involve an implantable device.)
Defibrillation systems might be needed in patients where the heart’s lower chambers (ventricles) are abnormal. Additionally, a patient who has had a heart attack or experienced cardiac arrest might need an ICD.
How are neurostimulation systems used?
Neurostimulation works to block pain by altering pain signals as they travel to the brain. The devices use a medical electrode to deliver electrical (usually, electromagnetic) stimulation to nerves in areas such as the spinal cord or brain.
In addition to providing relief for people suffering from severe and chronic pain, neurostimulation can be used to treat conditions such as epilepsy, Parkinson’s disease, depression, and migraine. Studies also show great potential in the use of stimulation of the vagus nerve to relieve hypertension.
While neurostimulation is sometimes used after other treatments have failed, there is growing move to make it a first (or at least early) line of defense in some conditions — for example, in place of prescription opioids for the treatment of pain.
Advantages of MP35N for Swiss Machined Electrodes
Medical device manufacturers generally choose implant-grade materials that meet American Society for Testing and Materials (ASTM) or ISO specifications.
For medical electrodes, MP35N is an implant-grade ASTM-specified alloy that is the material of choice due to its combination of properties including:
- High strength
- Corrosion resistance
- Electrical resistance
- Thermal conductivity
Typically work-hardened and comparable to 304 grade stainless steel in its tensile strength, MP35N provides the characteristics needed for both effective production in the hands of a skilled Swiss machine shop and a high-quality medical electrode in the end product.
Is precision CNC Swiss-style machining a good choice for your medical devices or other applications? Download our free guide Swiss Machine FAQs to learn more about it.