Have you ever had to tell the lab manager or physician that due to a cable being “dead in the water” … the case must cancel?
How can such an inexpensive piece of equipment cause such havoc? If handled properly, it doesn’t have to.
A fiber-optic cable is used for so many things in electrophysiology. It is a vital connection for the 3D mapping system and components as well as the recording system.
What is a fiber-optic cable?
It is an assembly similar to an electric cable, but containing one or more optical cables that are used to carry light. The optical fiber elements are typically individually coated with plastic layers and contained in a protective tube.
At one end of the system is a transmitter. This is the place of origin for information coming on to fiber-optic lines. The transmitter accepts coded electronic pulse information coming from copper wire. It then processes and translates that information into equivalently coded light pulses. A light-emitting diode (LED) or an injection-laser diode (ILD) can be used for generating the light pulses. Using a lens, the light pulses are funneled into the fiber-optic medium where they travel down the cable.
Think of a fiber cable in terms of very long cardboard roll (from the inside roll of paper towel) that is coated with a mirror on the inside. If you shine a flashlight in one end you can see light come out at the far end – even if it’s been bent around a corner.
Light pulses move easily down the fiber-optic line because of a principle known as total internal reflection. This principle of total internal reflection states that when the angle of incidence exceeds a critical value, light cannot get out of the glass; instead, the light bounces back in. When this principle is applied to the construction of the fiber-optic strand, it is possible to transmit information down fiber lines in the form of light pulses.
Fiber optic cables are particularly delicate, they can be cracked from too much tension during cable pulling or despooling. More frequently, a fracture is seen in the EP lab due to improper care. In the ideal setting, cables will be run through conduits in the floor or ceiling/boom; however, not all labs are set up permanently. In a mobile EP lab setting, cables are continually connected and disconnect. Each of these connections put all the cables at risk of failure due to wear and tear. Cables that are laid on the floor are often stepped on, tripped over, tangled in other equipment, or even run over by equipment and carts… no wonder they fail. When putting away for storage, if they are wound too tightly or pulled, this may lead to failure as well.
Sadly, this image is not from a google search, but what I saw in a lab when I was troubleshooting why they were unable to see any input on the monitors. I think we all know what the issue was, luckily they had an additional cable that we were able to swap out.
With these concerns with fragility – why do we use fiber-optic cables?
• SPEED: Fiber optic networks operate at high speeds
• BANDWIDTH: large carrying capacity
• DISTANCE: Signals can be transmitted further without needing to be “refreshed” or strengthened.
• RESISTANCE: Greater resistance to electromagnetic noise such as radios, motors, or other nearby cables.
• MAINTENANCE: Fiber optic cables cost much less to maintain.
In EP we often see gray and orange fiber-optic cables and they are usually duplex cables or two lines. Without getting into the weeds about the difference between the gray SD cables and the orange LC, know that the orange cables typically transmit to the display monitors such as from the mapping system to the screen input for the physician to view as well as from the live and review displays from the recording system. In the following image, the orange LC connector utilizes a latch as opposed to the SC (gray cable) locking tab. Having half the footprint of the SC connector gives it huge popularity in datacoms and other high-density patch applications, as its combination of small size and latch feature make it ideal for densely populated racks/panels.
The gray SC cables are typically used for data in the EP lab, such as from the recording system amplifier to CPU, the 3D mapping system amplifier to the CPU, and various other components of the 3D mapping system.
We all know how important it is to eliminate noise in the EP lab, so taking care of your cables is a good start.
Until next time,
April Felton
This week’s EP question:
What diagnostic EP electrode configuration increases mapping resolution?
- Irrigated Electrodes
- Smaller Electrodes
- Larger Electrodes
- Deflectable tips
Answer
Smaller Electrodes
Electrodes have become progressively smaller and more closely spaced in effort to reduce the sampled tissue size and increase the mapping resolution (the tissue area represented by each bipolar EGM). Notice the difference in the example below of a signal acquired with a diagnostic catheter vs. an 8mm ablation catheter. The signal from the ablation catheter appears stretched and low amplitude making it difficult to observe small fractionated electrograms.
