Tachycardias -- how dangerous?

[Tigger716]

Hi Doctor,

I understood that, in a healthy heart, tachycardias are benign.  The example of medication-induced tachycardias in a sound heart comes to mind.  But now I read that, even in a healthy heart, tachycardias can trigger serious, potentially life-threatening events.  Is this true?

Thanks.

[Tigger716]

Hi Doctor,

Thank you for both your answer and your question.

Here’s my situation.  I’m a 51-year-old non-drinking, non-smoking male who walks 2+ miles a day and is only mildly overweight.  I’ve been on lithium for 15 years, and I also take Wellbutrin, Celexa, Klonopin, and Risperdal (the last three in very small amounts).  Earlier this year, I was prescribed Synthroid 50 mcg for lithium-induced hypothyroidism.  A few months later, I began experiencing PVCs (diagnosed by EKG) and tachycardias with mild chest pain (self-diagnosed).  I’d never had heart problems until that point, and there aren’t any heart problems in my family.

Now here’s my dilemma.  I hate the somnolence and fatigue of hypothyroidism, and I’d like to continue taking Synthroid.  I’m one of the lucky ones to have crawled out of the bipolar pit, and hypothyroidism is a step backwards.  But if I continue taking it, isn’t there a risk that it can induce serious events even in a healthy heart?

My personal feeling is that, whatever the condition of my heart, the benefits of Synthroid outweigh the costs, at least for me.  If there’s a problem with my heart, there are certainly medications that can be administered side-by-side with Synthroid.  And if there’s no problem with my heart, a few skipped or rapid heartbeats – despite the risk -- is a small price to pay for relief from hypothyroidism.  

I’m having an echo-stress test this week with a cardiologist and then an appointment with my intern"verified."  In the meantime, I value your opinion – your insights are always keen and clearly expressed – and I’d like to hear your view.

Thanks.

[Michael J. McWilliams, M.D.]

But if I continue taking it, isn’t there a risk that it can induce serious events even in a healthy heart?

I agree with what you are saying (especially the part about me being "keen" -- just kidding).  The risk presented by normal heart PVCs is minimal.  You can look at a host of other things that we do -- second hand smoke, not enough exercise, too little sleep, fast food -- that increase our cardiovascular risks but we don't think them the same way.  Life is a serious of risk/benefit decisions.  It sounds like if the low dose synthroid is making you feel better and presents minimal increased risks.  Make sure you talk to your doctor about it, but I agree with your reasoning.

Thanks for posting.

[kitcurious]

I am no expert but have ..well may  have... hypothyroidism( I am HYPERthyroid at the moment ).  I don't think Synthroid, at the correct dose, should cause you tachycardia, but I know little about possible interactions - though there shouldn't be any in theory because the hormone you are taking is one you used to have more of by nature.
I believe, if you have long untreated hypothyroidism, it can actually damage the heart.

[Michael J. McWilliams, M.D.]

Tachycardia induced cardiomyopathies are pretty rare.   I have only seen a few so far. In general this is something that often look for but rarely see.

The classic examples are very, very rare.

Can you provide more information about what exactly you are concerned about?