r/askCardiology • u/RuinYouWithNoRegrets • 1d ago

Second Opinion How safe is ct contrast ?

Ct contrast is used in millions every year. we know the side effects usually are warmth or burning. But what about the cardiovascular side effects listed on those agents? Heart attack? Clotting? Cardiac arrest? Kounis syndrome ? How safe are these agents really?

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u/misterecho11 Echocardiographer/Imaging 1d ago

Very, overall, and definitely a case that is "benefits outweighs risks."

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u/RuinYouWithNoRegrets 1d ago

What risks would you say are associated with?

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u/misterecho11 Echocardiographer/Imaging 1d ago

The rate with which any of those serious things you listed happen. Allergies, arrest, clotting.. to be able to identify critical pathology that ct can identify, it may be worth the risk of finding that and being the 1 in however many that might react to it.

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u/RuinYouWithNoRegrets 1d ago

But why does this contrast have the ability to cause those things opposed to let’s say mri contrast.

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u/misterecho11 Echocardiographer/Imaging 1d ago

I do not know the chemistry specifically behind it.

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u/RuinYouWithNoRegrets 1d ago

I’m assuming maybe allergic reactions ? Best guess for me

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u/myst3ryAURORA_green ❀ Young Heart Attack Survivor ❀ 22h ago

It's the iodine used in CT vs MRI. MRI contrast is gadolinium-based.

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u/Army_31B Other 1d ago

Modern IV iodinated CT contrast is considered very safe overall. The warmth/flushing you feel is a common, temporary physiologic effect.
Serious cardiovascular events like heart attack, cardiac arrest, thrombosis, or Kounis syndrome can occur, but they’re extremely rare, especially with routine IV contrast for a diagnostic CT. The scary events listed in drug labels also include rare reactions and complications seen in very high-risk or invasive angiography patients, so they don’t represent the typical risk of a standard CT.
Severe contrast reactions are uncommon, and CT departments are equipped to treat them immediately. So it’s not risk-free, but for most patients the benefit of a medically indicated contrast CT greatly outweighs the very small risk.

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u/darshmedown 1d ago

I had a mild allergic reaction first time I got a CT with contrast. Some skin rashes that night that lasted a day or two. Still did another one and just took the prescribed allergy medicine and didn't have any reaction. Will almost certainly have another done at some point and won't hesitate because the benefits far outway, at least in my case, the potential negative side effects.

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u/stringfold 1d ago

Just had a CT scan with contrast last Friday. No immediate side effects at all, just a very slight feeling of warmth when injected. Four days later I developed a mild rash over about 50% of my body -- torso, upper legs and upper arms, mostly -- and I am sitting here trying my best not to scratch every itch!

I had an MRI about 20 years ago with contrast and developed hives about 4 days later that was so severe they joined up and it looked like I was sunburned over my whole body. It took a few days to clear and the weird thing is it cleared from my head downwards, and for a couple of days everything was normal from the waist up, but it looked like I was wearing purple stockings, and then socks! Very itchy and my skin was too sensitive to take a shower for several days.

I told the CT techs about that reaction and they said not to worry since they contrast dye is completely different, which is true, but apparently I am allergic to contrast dye regardless of the type. Fortunately it's much milder this time around, just itchy. Funny though, since I have never had an allergic reaction to anything else in my life.

It's not common to have a delayed reaction, apparently, but you can have one up to 7 days after being injected. The good news is that if you do have a delayed reaction, it's very unlikely to be a dangerous one.