Acquired LQT

My son just had an appointment with an EP cardiologist - we waited for this appt for almost 4 months. My son seems to be totally on the mend now, but we kept this appt as a follow up to make sure all was okay.  My son was experiencing lightheadedness and near syncope, especially during exercise - also extreme fatigue.  He had tunnel vision and white outs of vision.  We originally saw neurologists as they thought this was migraine related - a migraine specialist sent us to cardiology as he was slightly to moderately orthostatic.  The cardiologist we first saw said it was dehydration - cleared him for all sports.  Then he had near syncope during basketball so they ran more tests - echocardiogram, carotid ultrasound, holter monitor and stress test.  The stress test caused his bp to be really elevated - could not get a reading for 5 mins at the end, finally read it at 240/60.  The stress test EKG showed QTc of 461.  Everyone, including the EP cardiologist we just saw, tells us that his heart is perfect.  This new EP said there are lots of false positives of elevated QTcs during stress tests.  One cardiologist and a neurologist think this is an autonomic nervous system disorder. The new EP thinks it is depression - that even his migraines he had before all of this were not migraines, but were depression.  The depression reared its ugly head during all this, not before.  So we have no answers only contradictions.

My thoughts - the migraines were treated by many drugs.  He used to get many migraines, especially during or after strenuous exercise, so the neurologist were trying to get them under control.  My son took numerous doses of varied triptans - Axert was the last one he tried. These symptoms started right after that - blurred vision, tunnel vision, lightheadedness, near syncope.  I think the medication triggered acquired LQTS and that the more time he has been off these drugs, this has now gone away.  No one will agree with me or really even investigate this - maybe as we could blame some of them for insisting he take more and more of this drug, when it was what was causing these issues - ??  Anyway, my son was taking doxycycline at the same time and from my research, this may have caused the axert to be more concentrated in how his body was exposed to the drug.  

He is now taking prozac for the depression, seeing a counselor, and getting better. He is back to sports with no problems.  No migraines either - when he used to get them 5-4 x per month. Perhaps the prozac is keeping them at bay.  No lightheadedness, no near syncope, no vision problems - just recovering from missing 8 months of his life. No real answers, but we all are realizing that they might never be uncovered and the important thing is to move on.  

So - could this all have been from acquired LQTS?  Could this be from depression that had no symptoms?  Could this be some form of an autonomic nervous system problem?  We will take the recovery as it comes, enjoying having our son back, allowing him to participate in sports, and allow him to move on with his life!


This discussion is related to Borderline Long qt.

[is_something_wrong]

Well, I'm no expert, but I thought a QTc of 461 ms at max heart rate during stress test were perfect. The problem is; the formula for calculating QT (Bazett's formula, I will assume this was the formula they used) is overcorrecting at high heart rates and undercorrecting at low ones.

Assuming his heart rate was 200 bpm (300 msec) at peak exercise:

QTc 461 at rate 200 = uncorrected QT 252 msec. I didn't know that QT could narrow so much in the setting of prolonged QT, but again, I'm not an expert.

To compare, I followed my mom's stress test recently, and she had a QTc of 491 msec at heart rate 180 (she has a high max heart rate for age). She never had a syncope and she doesn't have LQT. Her resting QTc is 404 msec.

I have a resting QTc of approx 380 msec. Once I had a panic attack during a resting EKG, and my QTc were 459 msec. I don't know what my QT were during the stress test, I didn't care to ask the doctor (ignorance is bliss..).

You should express your concerns to the doctor, but this may very well be a mathematical problem, not a cardiac problem.

[lucy189]

Thanks for the reply and info - you seem to be far more of an expert than I am!   The stress EKG was labeled as abnormal and listed a prolonged QT interval. There were some t-wave irregularities.  There was accompanying lightheadedness and tunnel vision during this test.His max hr during the test was 185.  His bp was around 190/60 until he stopped - then the techs could not read if for over 5 mins and then finally could and it was 240/60.  Most of his resting EKGs showed a QTc of above 400 - 402, 420, 435.  I have no idea what it was at this last appt with the EP - he did not share this info with us.  I have complete confidence that what this EP said is correct - that my son is now fine. I just wish we knew what "it" was that made him so ill from October - April.