I have a few quick questions about Long QT Syndrome:
1.) If you have it can you have multiple gene mutations that are associated with LQT? I know that there are three main ones (LQT1-the exercise induced one, LQT2-the sudden startled induced one, and LQT3- the one that seems to get people while they sleep), but if you have one of them can you also have another?
2.) I've heard that for genetic testing they can find Long QT 80% of the time when it is really there. During that other 20% is that because there are other genes mutations we have yet to identify which cause it, or is it just because the test misses the big three mutations 20% of the time? In short, if you come back negative are you negative for LQT1-2- and 3? Or could it still actually be one of those three?
3.) If you have long QT syndrome would they most likely be able to induce V-tach/V-fib during a EP study, or could it be normal for someone with long qt syndrome to still not produce those arrhtymias during the test?
4.) If you do have LQT2 or LQT3 is it true that they would most likely recommend an ICD for your protection?
5.) Is having a relatively lower QTc interval reading more indicative of a particular LQT gene mutation, or could any severity of LQT have an equal chance of being any of the main gene mutations?
6.) Is it possible in some cases to have a catheter ablation that gets rid of the cause of the LQT, or would the syndrome only be treated with beta blockers and surgical devices (like the ICD) when deemed necessary?
7.) How long would it normally take to get a Long QT genetic test result back?
8.) Is it true that sleep is actually a trigger of dangerous arrythmias with the LQT3 gene, and would this also be true for LQ1 and LQT2 or just the LQT3 gene?
I am not a doctor but am being worked-up for a suspected case of LQTS. I will try and answer your questions based on my research and what I have been told. Since this is a patient-to-patient forum, you might also try posting on the expert forum in which a doctor will answer your questions (but only 2 questions per day are allowed).
1) No, you will have one type only (due to the particular mutation of that gene)
2) The test is very accurate for the major forms of LQTS that have been identified. The 20% "miss" rate is due to genes/combination of genes/environmental factors that have not yet been identified. In these cases clinical findings suggest the person has LQTS but they dont have one of the major (known) mutations of the gene
3) Im not sure.
4) No. It depends on your symptoms and your risk profile. Medications can also be used to treat LQT1-3
5) No. In fact, some people with LQTS have a "normal" QTc and 2% of the population have borderline high QTc intervals.
6) There is a surgery in which certain nerves that can cause the arrhythmia's are cut. I dont believe this is the same as an ablation.
7) My understanding is there are 2 companies in the USA that can test for the mutations. The "standard" turn-around time is 3 weeks or 7 weeks depending on the company
8) Yes, sleep is the trigger for LQT3. I do not know if sleep can also trigger LQT1-2.
Hmmm, I tried to post on the "ask a doctor" forum but I guess it ended back on here in the patient to patient section. This is probably a really dumb question but what did I do wrong? How exactly do you get a question posted on the "ask a doctor" forum?
They only except two new questions a day. It may be that if the quota is exceeded then the Q is posted here (but I would assume there would be a message asking you if you would like to do this - Im not too sure).
Yea, I think that's what happened, because this time it showed that the quota for heart related questions had been reached for the day. Anyways, just curious since you said that you are getting a workup for a suspected case of Long QT, what was your resting EKG QTc time when they decided to pursue this? Mine was 453ms in the absence of any DCM, HCM, or valve problems on my echo. Basically, my cardiologist is telling me that delayed repolarization is common in athletes and mine isn't that high, but I'm not so sure mine is totally attributable to being an athlete, because I have had the symptoms of palpitations and lightheadedness throughout my whole life (although generally mild). I'm going back to see him later this week to talk about an unrelated doubt of high blood pressure that we might need to put me on a beta blocker for, so I'm just wondering your opinion if you think 453 QTc with some moderate, infrequent palpitations is cause enough for concern that I am kind of justified in trying to push to get the epinephrine test done in the office to see if I would need to pursue genetic testing. As someone who might have long qt, do you think I'm right for pushing for this just to be safe, especially considering that I'm a runner, and have had some rare boubts of fluttering tachycardia while running through the years? See, I have a anxiety condition and I'm just trying to figure out if this is just me being a hypochondriac or if it's a valid concern. I'm 21. Thanks for your help.
There are two types of LQTS - genetic and acquired. The genetic form is very rare and other family members would have this too. Typical family history would include unexplained fainting, cardiac events, seizures, unexplained deaths. "if" you have the genetic form of LQTS (LQT1-3) then one of your parents would, one of their parents would, 50% chance that aunts/uncles would have it etc. This is what the genetic test looks for - a mutation in a gene that is inheritable and only present In the genetic form of LQTS. Do you have a family history that might suggest LQTS?
The acquired form is caused by electrolyte imbalances and certain medications. Look up qtdrugs.org for a list of medications that prolong the QTc interval.
Your QTc is borderline high. Mine was 460 ms which had my cardiologist concerned enough that she wanted a repeat EKG in a month. She originally believed mine may have been acquired because I was on a QTc prolonging drug during the first measurement but I was off the medication during the second EKG and my value was still borderline high. I have also had a few episodes of syncope and dizziness after exercise and have no family history on my fathers side so that warranted a stress echo and meeting with a genetic counsellor.
In your case, it would be important to look at family history that might suggest the genetic version of LQTS and also whether there is a chance of acquired LQTS (blood work to look at electrolyte levels, medications you may be on that could prolong the QTc interval) - if this is the case, this condition can be reversed. Depending on those results, a repeat EKG might be needed. If the value is still borderline high then follow up tests may be needed but most likely something like a stress test to start off with. I wouldn't think the epinephrine test would be the first test to consider, especially at this time when there are several less invasive tests that can be run (if deemed necessary).
FYI: there are only two companies in America that run the genetic test and they are very expensive (5-6k) and it is very, very challenging to get insurance companies to pay for this. This is where I am at now, waiting for the insurance company to determine whether they will pay for it (the request has been in the system for almost 3 weeks now).
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