Heart and thyroid

[kriskaydan]

.Hi there, I posted a few months back about a problem with an ECG result(in heart forums).  Basically, an ECG back in Dec showed was normal apart from a 'short pr interval'.  I have since had a 24 hr tape and waiting on an event monitor.  24 hr tape showed no abnormality, some supraventricular ectopics(which i never felt), but was told thats normal.  I have had palpitations on and off for years, but usually only related to stress/hormonal times in month, alcohol.  They were a bit more frequent towards end of last year, hence the ECG.

Anyway, cardiologist has seen results, and ruled out any serious causes of short pr interval(I was terrifeid it was WPW at first, but he sees no sign of that).  He is doing investigations to see what could be causing palpitations.

Then 3 weeks ago, after routine bloods at GP, was told my thyroid was low, TSH 28, T4 10.  Ive taken 100mcg thyroxine for 7 years since RAI treatment for graves disease.  Always been stable.  So have now upped my dose to 150mcg.

After all that history(sorry!), what Im wondering is could my thyroid have caused ECG changes, short pr interval?  I know that whether Ive been hypothyroid or hyperthyroid in past, I get palpitations, different heart rates... and Ive read that low thyroid can cause problems with hearts conduction system.  My GP thinks is going to send me for another ECG when thyroid levels normal again.

Thanks for any help,

H .

[goolarra]

I have WPW, which was controlled without heart meds all my life until I started thyroid meds.  In retrospect, however, I think it was being hypo, rather than the meds themselves that exacerbated my condition.  Since being euthyroid and on a stable dose for a few years, tachycardia episodes have been the best they've ever been since I was about 8 years old.

Both thyroid imbalance and thyroid meds can bring up heart issues that you never knew you had and may never have again once euthyroid.  Do you have palpitations or tachycardia (many people use the terms interchangeably) or both?

One caution:  That's a big increase.  Thyroid meds increases are usually made in 25 mcg intervals at most.  Labs should be run after 4-5 weeks and levels and symptoms re-evaluated to see if further increase is necessary.  This is especially important when heart issues are involved.

I don't think your thyroid caused the short PR interval.  It's most likely that was there already and the thyroid issues just brought it out.  As I said, there's a very good possibility that once your thyroid levels are stabilized again, your heart issues will be, too.  Another ECG with normal thyroid levels sounds like a good idea.    

[Red_Star]

Hyperthyroidism is one of the listed cause of a short PR interval.  If hypothyroidism does affect the PR interval, this will show up as a prolonged PR interval.