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Essential equipment: Angioplasty balloons
Purpose of equipment
These are mostly used to dilate blood vessels but can be equally useful for strictures in other systems.
Description
Although there is a huge variety of different angioplasty balloons, they all boil down to a straight catheter with an inflatable balloon at the distal end. All angioplasty balloons have a channel for a guidewire and a separate channel to allow balloon inflation/deflation.
There are two principal constructions:
Over the wire balloons
Most workhorse peripheral angioplasty balloons are constructed like this; the guidewire runs the whole length of the catheter from the hub to the tip ( Fig. 18.1 ).
Monorail – rapid exchange
The wire only runs through the distal 15–20 cm of the catheter. Hence, the catheter shaft is only the inflate/deflate channel ( Fig. 18.2 ). Monorail systems allow the use of shorter guidewires and catheter exchanges are much simpler and quicker. In addition, monorail systems tend to have a lower profile.
Modern angioplasty balloons are designed to minimize the balloon profile and therefore the size of the access sheath required. They will dilate the majority of lesions but every now and then, you will come across a resistant stenosis. The choice is then usually either a high-pressure balloon or a cutting angioplasty balloon. High-pressure balloons are made of a thicker material to sustain higher inflation pressures and often need a larger sheath.
A cutting angioplasty balloon is simply an angioplasty balloon with small razor blades/‘angiotomes’ incorporated into the balloon. These make shallow cuts into the fibrous tissue which is preventing the lesion from dilating. In general, cutting balloons have a much higher profile and are much more expensive than conventional balloons.
Measurements
There are seven measurements which you need to know. They are all usually on the front of the balloon packet.
Catheter dimensions
Catheter size (French, Fr)
This describes the sheath size recommended for the balloon.
Alarm
You may be able to squeeze a pristine balloon through a smaller sheath but removing it once it has been used is a different matter.
Catheter length (cm)
This is usually the tip to hub measurement but beware, the construction of some balloons will specify a working length and a total length. The working length is the value which determines whether your balloon is long enough to reach the target. The total length to the distal hub is the value which determines whether your guidewire is long enough to allow the balloon to be introduced and removed. There is usually a diagram showing the relevant lengths on the packaging.
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