Borderline Prolonged QT-c

[Mackinsluv]

I have a 10 year old daughter who had a catheter ablation done for SVT 6 months ago she has done really well until a week ago her school caled me and told me she was feeling very dizzy and lightheaded and her heart rate was at 148 this was after gym class so they had her sit with the nurse for a half hour to see if it came down it did come down to about 105 but she was still pretty light headed her pediatrician did not feel it was an SVT episode however I disagreed and followed up with her Cardiologist and he said the same thing. She had an ECG done while there and it says Borderline Prolonged Qt 464 Unconfirmed and the doc said nothing to worry about but I am because after they did the ablation they tried to stimulate an episode and they said it did not go into full episode but that there were 3 spots on her heart that quivered while trying to induce one. This is scary any help is greatly appreciated. There is a lot of heart problems on both sides of the family and my son who is almost recently had a seizure they were not sure they called it a fever seizure although he was not running a fever prior or after having it and there are a lot of family members who have had unexplained seizures and my great grandfather passed away at 45 from massive heart attack and they never knew he had problems till he passed. Thanks

[is_something_wrong]

Just to add something here, calculated QTc is not reliable when the heart rate is high, especially if the cause for the rapid heart rate is not physical activity. My QT time is usually low-normal (370-380 msec) and I've measured as low as 353 (see EKG attached to my profile if interested), but if I get bursts of rapid heart rate during the measuring (earlier I often got panic attacks in the doctor's office) it could be significantly higher. The QTc formula is just an equation and is known to over-correct QT at high heart rates.

If your/her cardiologist told you not to worry, I would trust that.

The "quivering" spots in the heart after ablation (when trying to induce the arrhythmia) are maybe spots firing PACs (I assume, since they ablated an atrial arrhythmia) when they gave adrenaline to provoke the arrhythmia? PACs are common and I guess everyone has quite a few PACs when they get an injection with adrenaline.

When the doctors do an EP study, they examine the heart quite carefully. I think without doubt that a Long QT syndrome would have been seen there. Another argument is, that when her heart rate went up to 300 with SVT, that itself makes long QT syndrome quite unlikely. In order for the heart to beat at 300 bpm, the QT time must necessarily be far below 200 msec, (300 bpm is 5 beats a second, and the QT time represents the systolic phase, where the heart pumps blood, and 1 sec/5 is 0,2 sec, 200 msec.) The heart also need to fill with blood, so the QT time must have been shorter than 200 msec. I don't think someone with LQTS would be able to have a heart rate that high because the potassium channels can't work that fast.

That said, the family history with unexplainable seizures should be investigated, but it sounds her heart already is examined by both cardiologist and electrophysiologist, so I'm not sure what more can be done..

Take care.

[MichelleP_3811]

My lord, I am not a doctor but I find that very odd that they can't classify it even to a small degree.  There is a clear distinction between wolf parkinsons white syndrome and avnrt though wpw is similar to avrt.  If she had Atrial Tachycardia that is something that might be a bit more difficult to diagnose.  But knowing where they ablated should give a general idea of the type it was.  I would ask if they ablated near the AVnode, on the wall for an accessory pathway between the atria and ventricles or if they did a pulmonary vein isolation which is what they sometimes do with Atrial Tachycardias if they can't induce.  You have a right to know what they did.  I would personally request a copy of the ablation report and mapping to see what it says.  But from what I understand WPW is probably not accurate because the beats don't generally go that high, the path is too long for the beat get that fast.  AVNRT does have high heart rates around 250 and maybe with your daughters young age I can see 300.  Adenosine generally works good on this type of tachycardia but I think it doesn't for atrial tachs and afib types so you may be able to rule those out but I am not a doctor so this is all just conjecture.  In the whole scheme of things you really don't need to know what type it was so long as it doesn't come back but it does sound like there was still some activity so personally I would ask for the report and see what it says they ablated.  Then maybe take that to a second cardiologist and see what they have to say.   Anyways, try not to worry too much if your daughter does have more tachycardia.  A fast beat needs to be managed but it isn't something that is going to cause her to drop dead in an instant.  I think my doctor said he only knows of one person ever dieing of SVT so the odds are your daughter will continue to live a long and healthy life.  

[Mackinsluv]

Wow, thanks for the quick response and when they said it quivered it was fluttering as if trying to go into an episode but it did not. My daughter does have high cholesterol and I monitor every meds she takes which right now are an Albuterol Inhaler only which she only started needing after the ablation she has wheezed ever since she got it done. Her SVT caused her heart to get up to 300 and usually she had to have Adenosine given to correct it which is why we did the ablation because they were occurring more frequently like that. I did ask him what type of SVT she had and was told that in children there is not different types that they break down under other names when they are older, but basically they were just sub- categories and they are all just SVT...confusing... I also think I am going to get a second opinion on her cardiologist I just don't feel as if he answers my questions and he even told me I did not need to make an appointment with him he just wanted me to e-mail him questions and then does not answer them all. Frustrating to say the least when it's your kids and you're worried. Thanks so much for the response!!!

[MichelleP_3811]

I am not a doctor so I can't diagnose your daughter but I will clarify that SVT and Heart Attack arise for different reasons.  A heart attack is generally caused by some sort of heart disease, most likely clogged arteries, something your daughter most likely need not worry about at this point.  Now if your great grandfather actually died of Cardiac Arrest as opposed to a Heart Attack he may have died of Ventricular Fibrillation but again this generally arises due to some sort of heart disease so I doubt your daughter is at risk in that regard either.  It is likely your daughter had a run of the mill SVT.  SVT in someone as young as your daughter is likely from a congenital cause.  There are extra fibers in her heart that can conduct electricity from which the eletrical signal can get caught in a loop and cause a fast beat.  I had AVNRT which is one of the most common of svts and is characterized by an extra fiber leading into the AVnode.  There are other types as well and only her doctor can tell you which type it was.  But generally the condition is not dangerous in an otherwise healthy heart.  Over time with repeat or prolonged episodes a person may run the risk of developing congestive heart failure but we are talking years of repeat episodes and still the issues not likely arising until one reaches their sixties if at all.  My type of svt would cause a beat of 230bpm.  This is a beat fast enough to warrent attention but I was told by my cardiologist that beats as low as 150 really aren't that much of a concern at all.  Obviously one would want to find out the cause and work to correct it but just to ease your mind that the beat rate isn't anything to get overly scared over.  The human heart is a very resilient muscle that can take a lot and find ways to work around any issues so no need to overly worry.  

As for what happened with your daughter no one can likely say for sure.  It is possible she got a bit dehydrated and caused the fast beat and light headedness.   It is also possible her heart is healing itself of the ablation.  There is a higher reoccurance rate in young people than in older people due to the fact that young people's hearts are still maturing.  If this is the case generally a second ablation would seal the deal so to speak.  But it doesn't sound like the cardiolgist thinks this is what is happening so I would say keep an eye on her and have her let you know if any more symptoms come up but in general it is likely she just overworked herself.

As for the long QT if the doctor wasn't concened about it then try not to worry.  Is your daugher on any allergy meds?  These types of meds can actually prolong one's QT segment so if you are concerned about it have her avoid allergy and cold medicines.  Finally I am not sure what they mean by quivering.  I know when I had my ablation they albated the accessory pathway and were not able to induce an episode but they also made sure to ablate any dual physiology meaing any spot in the heart that seemed to be conducting even if it wasn't causing tachycardia.  From what I have read it isn't necessary to fully eliminate any dual physiology to cure a person of svt so maybe your daughters' doctor saw fit not to bother.  That said, I am not sure that is what they were talking about so maybe you want to get the doctor to clarify what they meant by the quivering and if it is something that needs to be monitored because it could progress into something else.  But the doctor who gave you this information is really the best person to talk to on the issue though I would be interested to hear what they meant by quivering.

As for seziures, I don't think that is indicative of a heart condition though I think dysautonomia may cause seziures and fast heart rates and fainting. If you are interested in learning more then research the disorder but it is more of a disorder of the brain than it is an issue with the heart.  Though it is very likely your daughter was deyhdrated or had other electrolyte imbalances that caused her heart rate to raise and not go down.  To be certain all is well in that area take her to her GP and get a full blood panel done.  But try not to worry too much.  I am sure your daughter is just fine.  Take care and keep us posted on how she is doing.