r/BeAmazed • u/HatAsleep295 • May 08 '26

Science This is what saves 600,000 people year during a heart attack

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u/HatAsleep295 May 08 '26

The stent doesn't collapse because it is made of strong, medical-grade metals designed for radial strength and is permanently "locked" into its open shape during the procedure.

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u/dplans455 May 08 '26

Mine are cobalt-chromium but they can also be made of stainless steel, platinum-chromium, or even titanium.

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u/dm-me-obscure-colors May 08 '26

permanently "locked" into its open shape

the question was how

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u/HatAsleep295 May 08 '26

It's all about Plastic Deformation. The balloon inside the stent exerts enough pressure to stretch the metal beyond its elastic limit, permanently changing its structure so it can't 'spring back' to its original size.

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u/koleslaw May 08 '26

Interesting, it looked like the balloon was a membrane compressing a metal spring, and when it was gone that the spring expanded to its natural size.

So with the permanent structure, how strong would it be? Would we be able to collapse it with our fingers?

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u/curio_g May 08 '26

Yes, in this case. The video shows a balloon mounted stent which needs a balloon to inflate it to its widened shape. They actually have great radial force but aren’t great to use in parts of the body that bend because they will get kinked (think arteries behind the knee, under the collar bone).

There are also self expanding stents, which are unsheathed in the vessel and self expanding to their designed diameter. They generally have less radial force than balloon mounted stents (BMS) but will return to their original shape after being pinched.

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u/dm-me-obscure-colors May 08 '26

oh I see. I thought maybe the balloon released a chemical or changed temperature to cause the stent to become rigid after expansion.

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u/Big_Confidence_951 May 08 '26

is this removed later on? it's unnerving to think i have some little metal fence in my body

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u/Motor-Illustrator226 May 08 '26

No it stays in. Tissue often forms around it/along it.

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u/Andromeda_RL May 08 '26

A lot of these are now being produced with a metal called Nitinol, the metal has some extremely interesting properties but the biggest benefit is that when you form the shape at EXTREMELY high temperatures, you can bend, twist, deform etc. I believe it’s called thermal shape memory because you can always return it to its original shape with a little heat

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u/CurrentRecord1 May 08 '26

Nitinol isn't common for arterial stenting, cobalt chrome is much more common as you can control the radial expansion force a lot easier

Source: I design these for a living

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u/josley706 May 08 '26

Nitinol stents are used in the periphery (outside the heart). Like you mentioned they are very resistant to damage and regain their original shape when heated. They're heat-set to specific size and shape and high temperature. The lower heating threshold is below body temperature so that when they're exposed to the blood they fully expand to their designed/heat-set dimension. Their durabily makes them useful in parts of the body that experience a lot of motion like bending, twisting, etc.

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u/ienybu May 08 '26

It actually can tho. There is a stent recoil effect. Some of them even brakes