Long QT question

Hi,
   My 13 year old daughter was tagged on two seperate machines as being borderline Long QT.  Both of them were looked at by two different cardiologists, and were deemed as normal.  Her pediatric cardiologist said she was at 420 mm's, which is normal.  She did provide me with a list of drugs to be avoided, only because I was interested.  My daugther was prescribed Azithromycin on Monday due to bronchitis, and this drug is on this list, as a number 2, which says that it may prolong the QT interval.  She is a runner in cross country, and is practicing for a meet on Friday, which means she will be pushing herself to the limit this week physically, do you think it is safe for her to be running in this way, while she is on this particular drug?  Her cardiologist has assured me that she dosen't think that my daughter has, or is predisposed to Long QT, I only worry about being on a drug such as this, while she is running so hard, being that she was tagged on two machines, and this is still in the back of my mind.  Also, when a drug says that it may prolong the QT interval, does this mean it's a temporary thing, or can it be permanent?  I wouldn't want to give her a drug that had such an effect, even on a normal heart, since a couple weeks ago we were so worried about her having that very thing!  Thank you so much, Val

[Michael J. McWilliams, M.D.]

Hi Val,

She is a runner in cross country, and is practicing for a meet on Friday, which means she will be pushing herself to the limit this week physically, do you think it is safe for her to be running in this way, while she is on this particular drug?

I can't make any EKG based decisions without seeing the EKG (I know you know that).  If you are not comfortable with the opinions of two cardiologists,  you may want to ask for a consult from a pediatric electrophsyiologist (cardiologist that specializes in heart rhythm disorders).  As a parent, if you are going to worry about this, get another opinion for your peace of mind.

Azithromycin is consider a low risk QT prolonging drugs -- some references say that it does not prolong QT interval.

EKG machines over call long QTs -- it is difficult to measure.  When I am the EKG reader for the hospital, I am often crossing out prolonged QT.

If your cardiologist has assured it that the QT is not prolonged, that is pretty strong and they must be pretty certain.

Also, when a drug says that it may prolong the QT interval, does this mean it's a temporary thing, or can it be permanent?

The drugs that prolong QT in people at risk only do so when the medication is in the body.  It is not permanent.

I hope this helps.  Thanks for posting.

[valger59]

Yes, it does help, thank you~~but I was wondering if generally speaking, it is considered ok to run at the level that a cross country runner does, with this particular drug in their system.  I feel pretty comfortable that two cardiologists have seen her EKG's, and both of them declared it as 'normal', and the first one was also an electrophysyiologist, according to the second pediatric cardiologist, that we visited.  We didn't see the first one, he just looked at her EKG, which was done at the doctors office.  Now that I am aware of the drugs that can prolong the QT interval, I worry that she shouldn't be running with this drug in her system.  Even if it does prolong the interval, should it still be safe to run in an otherwise healthy heart?  I also worry that 420 mm's is on the high end of normal, since I have read different things in different places.  Her cardiologist said it was normal, but online I read where 423 was on the high end of normal, and then in another place I read where 420 is completely normal in females.  Thank you very much, Val

[Michael J. McWilliams, M.D.]

If I had a patient with a normal QT on their EKG and no family history or personal history suggestive of long QT syndrome,  I would have no problem allowing them to run with azithromycin.  Azithromycin is not considered a higher risk QT prolonger and if it was, it only affects people with with a tendency toward long QTs.

I hope this helps.

[stevie_wonder]

Hi,
Long QT Syndrome diagnosis is not an exact science. If someone doesn't have an extraordinary prolonged QT interval (without drug influence, electrolyte imbalances, or other medical reasons for a prolonged QT interval) on their resting ECG, diagnosis is simply based on family history, other ECG abnormalities involving T waves, symptoms (fainting, near-fainting, arrythmias, cardiac arrest). There is a point system that many doctors used and will order genetic testing if necessary. But even genetic testing is only 60-70% accurate as only that many genes have been identified. There is a large overlap of QT intervals with LQTS and the normal population from 410-460.  Doctors use holter monitors to see how the QT interval changes throughout the day and at different heart rates. Exercise stress testing can be useful in alot of cases too. There are also drug challenge tests where doctors give patients certain medications to see how the QT interval reacts. I would really think it is safe to say that your daughter does not have LQTS mainly because of lack of symptomatic family members.
Keep your daughter hydrated for a couple of hours before the race, and as the doctor said, this medication is only weakly associated with prolonging the QT interval.
Take care,
Stevie

[valger59]

Wow~~
   You guys have been beyond helpful, thank you so much!  I basically just wanted to say thanks and let you know what a difference you have made in taking the time to help me with this!  She ran today, and felt fine, so that is good news!  Thank you again so much!  Thanks for letting me know about keeping hydrated, I'll make sure to make a special effort to do that!  Thanks, Val