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Graves disease, RAI for thyroid, ECG, thyroxine, cardiac arrest. Do i have I have ectopics change?

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Cardiologist, Interventional
Practicing since : 1996
Answered : 192 Questions
Advice re palpitations/short pr interval :

Hi there,

37 yr old female, and had palpitaitons on and off since graves disease 8 years ago. Had XXXXXXX for thyroid, and been underactive since. Lately had more palpitaitons than normal, had ECG done. Showed short pr interval. No other abnormalites. Cardiologist recommended 24 hr tape and event monitor. 24 hr tape showed supraventricular extrasystoles.Had no symptoms. Im currently wearing an event monitor, had a couple of slight skipped beat feeling, which have been checked and are occasional ectopic beats. Technician says benign. Still wearing event monitor for 2 weeks, to try and catch more concerning palpitations.

I have 2 types of palpitations, missed /skipped beat ones, which last a second, and fluttery one, which last 5-10 seconds.Its this one that scares me. If have already been seen to be ectopic beats Im having, is it likely this other type of palpitation is ectopic beats also? It feels different.

All ECGs done lately show short pr interval, around 104. If event monitor shows only ectopics, and Im told are benign, should I forget about the pr interval? Is it serious? Ive been told that as there are no other abnormalites with heart, short pr means nothing on its own. Does the fact I have ectopics change that?

My palpitations have never changed, always same type feelings. Thyroid has been stable for years, but found out in February that it was really low. Increased my thyroxine dose, then it was too high, so Im back to lower dose. I know in the past my thyroid being out of whack gives me palpitations, whether high or low. So I do think the last few months this has had an affect, and that when stable, palpitations should be better again. I accept ectopics benign, but the short pr worries me.

No other health issues!. Had guillan barre syndrome when 5 years old, and cardiac arrest due to that. Perhaps this is why I worry about my heart a bit more that I might!

I am just looking for reassurance really.

Thank you for your time,

Posted Tue, 22 May 2012 in Heart Failure
Answered by Dr. Raja Sekhar Varma 35 hours later
Thank you for the query.

PR interval refers to the time taken for the electrical impulse to get generated in the sinus node, get conducted throughout the atria and reach the ventricle after passing through the AV node (where there is a small slowing of conduction). The normal time is 120-200ms.

A short PR interval without a XXXXXXX wave usually is a very benign condition due to accelerated conduction (because of high sympathetic drive, less parasympathetic drive, etc). Rarely, it can be due to the presence of atrio-Hisian tracts that bypass the AV node.

In the absence of a documented tachycardia, there is really no need to worry about the short PR interval. However, if a tachycardia has been seen, then you need to undergo a complete Electrophysiological study and further treatment as indicated.

You are absolutely correct in supposing that changes in the thyroid function can result in these palpitations. While benign extra-systoles are common, sometimes these can trigger arrhythmias like atrial fibrillation, AVRT or AVNRT. In that case, again, you need an EP study and ablation treatment. Of course, it goes without saying that you need to control the thyroid status with suitable optimization of the hormone therapy.

If the event monitor does not catch the prolonged palpitations, then you have the option of having an implanted loop recorder which will monitor your heart beats for months together. Or, you can go in for an invasive electro-physiological study.

If you can upload a scanned image of the ECG to this website, I can have a look at it and give you my specific opinion.

At the moment, however, I can reassure you that brief and occasional extra systoles are benign and do not need any specific treatment other than controlling and normalizing your thyroid function.

I hope this answers your query. Feel free to contact me for any further clarifications.
With regards,
Dr Raja Sekhar Varma, MD,DM
Consultant Interventional Cardiologist
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