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Questions about Long QT, help please
Hi - I have some questions about long QT syndrome. I've recently had 3 EKGs because of palpitations and a fast heartbeat. I've asked the doctor who did them about long QT and each time he said there was nothing showing I had it. My QT/QTc was 350/418 on the first one I believe, on the second 362/425 and on the third 358/440. Heartbeat was 86, 83 and 91 respectively. The last one is the one that got me worried, because apparently 440 is the limit for normal. I am female by the way and have no family history of the disease. I have fainted twice before, but both times were for known reasons.
In your opinion, should I press my doctor for more tests, or am I in the clear? I'm terrified of Long QT to be honest, any help is appreciated.
In your opinion, should I press my doctor for more tests, or am I in the clear? I'm terrified of Long QT to be honest, any help is appreciated.
I totally understand having anxiety regarding LQT syndrome. My brother and cousin both died of LQT several years ago (when not much was known about the syndrome), then the rest of my extended family had blood tests to see if we held the gene. I have LQTS 1, although apart from having massive panic attacks (which I think is related to worrying about this), I have never actually passed out or had a symptom. Along with this, I now have 3 children who all have extended QT intervals, particularly my 3 year old daughter. We are all on beta blockers. In the last 2 months I have had crippling anxiety regarding this. I worry when I am driving I will pass out while I have my children with me, or that my daughter might and I will have to use the defib on her. It's all real and very scary, but I guess I have to remember that there is always an element of "what if" in all we do, and that is life. My corrected qt interval at my last appointment was 427. Would love some feedback
Hi all, sorry for not posting back. I'm feeling much better about it now, thanks for the help. I realize I was paranoid about it, I have an anxiety disorder though which these days has become health anxiety. I'm working on getting better.
Thanks again.
Thanks again.
Mine was going higher from the flecainide i was on. Also wasn't producing great t wave from the medicine soooooo they took me off of it. Coming off of it was like death... :( feel much better now
OK, I won't correct them with another equation.
I believe the "gold standard" in diagnosing LQTS is a genetic test where they look for mutations in the genes controlling potassium outflow from the cells. As potassium flows out, calcium flows in, and if the potassium channels are too "slow" (look at them as narrow), the cells may be overfilled with calcium, which can trigger arrhythmias. The problem is, those tests are not exact and diagnosing LQTS with 100% certainty is impossible.
A common misunderstanding is that a few EKGs that show prolonged QTc is diagnostic of LQTS or necessarily dangerous. It really isn't. First, the equation may overcorrect, second, you may have a prolonged QT without any genetic dysfunctions. The problem is, however, that a prolonged QT can cause trouble even without genetic LQTS. But if so, we are not talking QT times in the 440-470s. As far as I know, the risk of TdP begin to increase with QT above 500 msec and is substantial if the QT is above 600 msec. But, there is a safety margin, as the QT may prolong in individual settings, say your potassium is low, you take meds that prolong it, anything. And, at night, when we all experience bradycardia, the QT time will prolong some.
It's the uncorrected QT that may cause trouble, not the corrected QT. As mentioned earlier, normal people can develop TdP if we develop total heart block with a heart rate of 20 bpm, for example.
I believe we all have our unique QT shortening in response to an increased heart rate. My QT is fairly "flat", it doesn't decrease so much with increased heart rate and doesn't increase so much with slow heart rate (which will make the QTc decrease with slow heart rate and increase with rapid). We are all different.
I believe the "gold standard" in diagnosing LQTS is a genetic test where they look for mutations in the genes controlling potassium outflow from the cells. As potassium flows out, calcium flows in, and if the potassium channels are too "slow" (look at them as narrow), the cells may be overfilled with calcium, which can trigger arrhythmias. The problem is, those tests are not exact and diagnosing LQTS with 100% certainty is impossible.
A common misunderstanding is that a few EKGs that show prolonged QTc is diagnostic of LQTS or necessarily dangerous. It really isn't. First, the equation may overcorrect, second, you may have a prolonged QT without any genetic dysfunctions. The problem is, however, that a prolonged QT can cause trouble even without genetic LQTS. But if so, we are not talking QT times in the 440-470s. As far as I know, the risk of TdP begin to increase with QT above 500 msec and is substantial if the QT is above 600 msec. But, there is a safety margin, as the QT may prolong in individual settings, say your potassium is low, you take meds that prolong it, anything. And, at night, when we all experience bradycardia, the QT time will prolong some.
It's the uncorrected QT that may cause trouble, not the corrected QT. As mentioned earlier, normal people can develop TdP if we develop total heart block with a heart rate of 20 bpm, for example.
I believe we all have our unique QT shortening in response to an increased heart rate. My QT is fairly "flat", it doesn't decrease so much with increased heart rate and doesn't increase so much with slow heart rate (which will make the QTc decrease with slow heart rate and increase with rapid). We are all different.
wow thanks for doing that; interesting to see the corrected QT's isn't it? more numbers and a different result? I stay confused enough as it is... a different formula may really confuse me...
I'm interested in knowing how they really dx someone with LQTS because it was mentioned to me about my symptoms and numbers...(I gave up awhile ago; too sick and tired to fight anymore)
so when do we question our dr's and make sure they're not missing something like this and when to be worried about what a machine prints out? how do we put our minds at ease...
I'm interested in knowing how they really dx someone with LQTS because it was mentioned to me about my symptoms and numbers...(I gave up awhile ago; too sick and tired to fight anymore)
so when do we question our dr's and make sure they're not missing something like this and when to be worried about what a machine prints out? how do we put our minds at ease...
Hi, I hope you are feeling better :)
I just wanted to say, some of your QT variance is caused by different equations used by different EKG machines to calculate corrected QT.
To sum up (I copy your results and correct them with standard "bazett's formula":
Pre-Ablation
QT/QTC 380/350 HR 51 (Bazett used)
QT/QTC 434/411 HR 54 (Bazett used)
QT/QTC 420/417 HR 58 (Bazett QTc 413 msec)
QT/QTC 430/430 HR 60 (Heart rate 60, no correction needed)
QT/QTC 402/426 HR 74 (Bazett QTc 446 msec)
QT/QTC 384/437 HR 78 (Bazett used)
QT/QTC 404/439 HR 80 (Bazett QTc 466 msec)
QT/QTC 398/473 HR 85 (Bazett used)
Post-Ablation and ICD implant
QT/QTC 410/418 HR 65 (Bazett QTc 427 msec)
QT/QTC 420/436 HR 65 (Bazett used)
QT/QTC 361/411 HR 92 (Bazett QTc 447 msec)
So - there is a lot of debate which formula is the correct one to use. One formula can provide the Long QT diagnosis where another will not at all. If you want, I can correct all your numbers with the Fredericia formula, which will provide completely different results).
Take care!
I just wanted to say, some of your QT variance is caused by different equations used by different EKG machines to calculate corrected QT.
To sum up (I copy your results and correct them with standard "bazett's formula":
Pre-Ablation
QT/QTC 380/350 HR 51 (Bazett used)
QT/QTC 434/411 HR 54 (Bazett used)
QT/QTC 420/417 HR 58 (Bazett QTc 413 msec)
QT/QTC 430/430 HR 60 (Heart rate 60, no correction needed)
QT/QTC 402/426 HR 74 (Bazett QTc 446 msec)
QT/QTC 384/437 HR 78 (Bazett used)
QT/QTC 404/439 HR 80 (Bazett QTc 466 msec)
QT/QTC 398/473 HR 85 (Bazett used)
Post-Ablation and ICD implant
QT/QTC 410/418 HR 65 (Bazett QTc 427 msec)
QT/QTC 420/436 HR 65 (Bazett used)
QT/QTC 361/411 HR 92 (Bazett QTc 447 msec)
So - there is a lot of debate which formula is the correct one to use. One formula can provide the Long QT diagnosis where another will not at all. If you want, I can correct all your numbers with the Fredericia formula, which will provide completely different results).
Take care!
like IST my QT/QTc has been pretty varied; I have many 400-473 and I have classic symptoms of LQTS - I believe I scored a 6 or 7 with symptoms but the dr's said I didn't have it after looking at all my tests together...I think mine is caused by my cardiomyopathy
It is interesting to see others numbers from others ekg's; here's some of mine just to compare
Pre-Ablation
QT/QTC 380/350 HR 51
QT/QTC 434/411 HR 54
QT/QTC 420/417 HR 58
QT/QTC 430/430 HR 60
QT/QTC 402/426 HR 74
QT/QTC 384/437 HR 78
QT/QTC 404/439 HR 80
QT/QTC 398/473 HR 85
Post-Ablation and ICD implant
QT/QTC 410/418 HR 65
QT/QTC 420/436 HR 65
QT/QTC 361/411 HR 92
there are quite a few meds that can cause QT to be prolonged; are you taking any meds? sorry if I missed it...it's early and not fully awake.
diarrhea and vomiting can a loss of potassium which can cause it to happen also...have you had a full electrolyte panel; thyroid; sodium etc done to make sure those are on par?
btw; what's the cause of your fainting? if you have a fainting disorder it may be the reason since fainting could be in the neurological disorders; def keep in contact with your dr and ask about it
It is interesting to see others numbers from others ekg's; here's some of mine just to compare
Pre-Ablation
QT/QTC 380/350 HR 51
QT/QTC 434/411 HR 54
QT/QTC 420/417 HR 58
QT/QTC 430/430 HR 60
QT/QTC 402/426 HR 74
QT/QTC 384/437 HR 78
QT/QTC 404/439 HR 80
QT/QTC 398/473 HR 85
Post-Ablation and ICD implant
QT/QTC 410/418 HR 65
QT/QTC 420/436 HR 65
QT/QTC 361/411 HR 92
there are quite a few meds that can cause QT to be prolonged; are you taking any meds? sorry if I missed it...it's early and not fully awake.
diarrhea and vomiting can a loss of potassium which can cause it to happen also...have you had a full electrolyte panel; thyroid; sodium etc done to make sure those are on par?
btw; what's the cause of your fainting? if you have a fainting disorder it may be the reason since fainting could be in the neurological disorders; def keep in contact with your dr and ask about it
My most recent ekg showed a qt interval in the mid 400's or so, and my EP said under 500 was okay. He had a little instrument in his pocket and measured the length of the wave on the ekg print out. He is apparently watching it while I am on the Norpace anti-arrythmic drug.
First, the tables you've found for upper limit of normal QT are all based on the Bazett's formula for correcting QT interval. You can calculate it yourself or use online calculators, there are lots of them. But my point is, at high heart rates, the formula tends to over-estimate QT. You need to remember, this is just a mathematical approach, the formula doesn't say what your real QT time is.
I can refer some of my EKG results:
QT 330, QTc 358 HR 71
QT 354, QTc 393 HR 74
QT 370, QTc 400 HR 70
QT 334, QTc 398 HR 85
QT 309, QTc 453 HR 129 (panic attack)
QT 319, QTc 432 HR 110 (3 minutes later)
QT 342, QTc 419 HR 90 (10 minutes later)
As you can see from the last three results, as my HR decreased, my uncorrected QT increased (as it should do) but my corrected QT time dropped. This is also a sign that the formula is over-correcting.
I can refer some of my EKG results:
QT 330, QTc 358 HR 71
QT 354, QTc 393 HR 74
QT 370, QTc 400 HR 70
QT 334, QTc 398 HR 85
QT 309, QTc 453 HR 129 (panic attack)
QT 319, QTc 432 HR 110 (3 minutes later)
QT 342, QTc 419 HR 90 (10 minutes later)
As you can see from the last three results, as my HR decreased, my uncorrected QT increased (as it should do) but my corrected QT time dropped. This is also a sign that the formula is over-correcting.
2 Comments
This was a wonderful explanation. I feel much better myself after reading this. My corrected QT 436, but I was at the hospital due to a panic attack. The did state that I have lower bundle branch blockage, but my QT is usually 403-408.
This was a wonderful explanation. I feel much better myself after reading this. My corrected QT 436, but I was at the hospital due to a panic attack. The did state that I have lower bundle branch blockage, but my QT is usually 403-408.
p.s might i ad the week before starting flecainide i had ekg too and numbers were much lower QT369 QCT392 wonder why such the increase?
my last ekg was on 10/29/12 and my numbers were QT438 QCT437 and im sooo scared too. my resting heartbeat was 65bpm. also i had been on flecainide for 4 days at the time of the ekg test. i have a stress test next week and wonder what its going to be then. i havent had my heart rate up by excersise in over 10 years unless the afib or anxiety causes it to race. im scared what its going to do on the stress test tredmill?? and wonder what my numbers will be for my QT & QCT? i dont want any vfib or any v-anything tacy to start up uhggg
Thanks a lot, that helped put my mind at rest. Concerning my last result, through my googling I found that at heart rate 90 which I had, the uncorrected QT should be 360 or less...mine was 358 but isn't that pushing it a bit? I realize I'm a hypochondriac but I just can't shake this feeling that something might be wrong.
I wouldn't worry about this at all.
Your QT time seems normal (by the way, the upper limit of normal is higher in females than males). You can't completely trust the corrected QT interval, if your heart rate is on the high side. My QTc also increase when the heart rate is higher, at 60 bpm I'm usually at 360-370 msec or so, but at 120-130 bpm it can go higher than 440 msec. It's a fairly known fact that Bazett's formula can overcorrect QT at high heart rates. I remember when my mom had a stress test done, baseline QTc was 410 msec, but at 180 bpm, her QTc was 495 msec and her cardiologist wasn't concerned at all.
Yes, sinus arrhythmia can affect the corrected QT interval (making it falsely higher), as it's the longest registered QT interval in a single complex that is corrected with the "total" heart rate.
It's the uncorrected QT time that counts, regarding arrhythmias. The correction is just done to estimate what your QT time would have been if your heart rate was 60 bpm. That's why people with extreme bradycardia (in the setting of severe hypothermia, total heart blocks, etc) may develop torsades de pointes even without LQTS.
LQTS also usually causes other T wave changes (biphasic or notched T wave, as what seems to be the U wave actually is a double T wave). If you are in doubt or afraid, let a cardiologist interpret your EKG. In the meantime I wouldn't worry.
Your QT time seems normal (by the way, the upper limit of normal is higher in females than males). You can't completely trust the corrected QT interval, if your heart rate is on the high side. My QTc also increase when the heart rate is higher, at 60 bpm I'm usually at 360-370 msec or so, but at 120-130 bpm it can go higher than 440 msec. It's a fairly known fact that Bazett's formula can overcorrect QT at high heart rates. I remember when my mom had a stress test done, baseline QTc was 410 msec, but at 180 bpm, her QTc was 495 msec and her cardiologist wasn't concerned at all.
Yes, sinus arrhythmia can affect the corrected QT interval (making it falsely higher), as it's the longest registered QT interval in a single complex that is corrected with the "total" heart rate.
It's the uncorrected QT time that counts, regarding arrhythmias. The correction is just done to estimate what your QT time would have been if your heart rate was 60 bpm. That's why people with extreme bradycardia (in the setting of severe hypothermia, total heart blocks, etc) may develop torsades de pointes even without LQTS.
LQTS also usually causes other T wave changes (biphasic or notched T wave, as what seems to be the U wave actually is a double T wave). If you are in doubt or afraid, let a cardiologist interpret your EKG. In the meantime I wouldn't worry.
Hi, I have read quite a few posts on this site regarding people who are aware of prolonged QT syndrome but most likely don't have the problem. After reading yours today I thought I would like to say a few things to allay your fears.
I am a victim of few kinds of arrhythmias; I have VT, junctional ectopic tachycardia and also Long QT. I have suffered one episode of extremely fast heart beat called Torsades de Pointes.(TdP) quite similar to VF a couple of years ago. This latter type is a result of prolonged QT. I have had many years of long QT shown on ECG whereby my EP was concerned about but didn't act till it was more prolonged and obvious. LQTS is hard to diagnose and seems to be seen in females more than men. But there are usually a family or hereditary trend.
My QTc (corrected QT measured at fast HR) was usually 530ms to 660ms. The shortest was usually 485 and up.
Most drs wouldn't be too concerned with borderline readings cos at some time or other we do get slightly longer measurements. They are not too bothered if it's not seen on every ECG taken.
One thing the EP will watch out for is family history of sudden death. (I have 2 brothers who passed on suddenly one at infancy and other one early 50s).
Then your ECG tracings would show tell tale signs of U waves. This is a rather important sign, cos when I had my deadly tachycardia the TdP few years back, the U wave was prominent other than just the QTc measurement.
Your dr may also take your blood test to see how your potassium level is like.
Frankly drs usually don't jump up at a QTc of 440 to 470. They probably will sit up when they see 500msec and above several timesin a row on ECGs.
So, I hope it helps you somewhat to relax a little....but if you feel your fast heart rate is accompanied by dizziness, do go see your cardiologist soon. They maybe not the sinister sort cos there are many types of arrhythmias...but it's always good to check to allay your fears and set your mind at ease?
I have an ICD implanted for many years and taking beta blocker as well as arrhythmia meds to prevent untoward attacks. But I know I am always looking over my shoulder to make sure I won't have "rude shocks"!!
If you feel you want some assurance feel free to contact me.? I hope you feel better soon...good luck. God bless.
I am a victim of few kinds of arrhythmias; I have VT, junctional ectopic tachycardia and also Long QT. I have suffered one episode of extremely fast heart beat called Torsades de Pointes.(TdP) quite similar to VF a couple of years ago. This latter type is a result of prolonged QT. I have had many years of long QT shown on ECG whereby my EP was concerned about but didn't act till it was more prolonged and obvious. LQTS is hard to diagnose and seems to be seen in females more than men. But there are usually a family or hereditary trend.
My QTc (corrected QT measured at fast HR) was usually 530ms to 660ms. The shortest was usually 485 and up.
Most drs wouldn't be too concerned with borderline readings cos at some time or other we do get slightly longer measurements. They are not too bothered if it's not seen on every ECG taken.
One thing the EP will watch out for is family history of sudden death. (I have 2 brothers who passed on suddenly one at infancy and other one early 50s).
Then your ECG tracings would show tell tale signs of U waves. This is a rather important sign, cos when I had my deadly tachycardia the TdP few years back, the U wave was prominent other than just the QTc measurement.
Your dr may also take your blood test to see how your potassium level is like.
Frankly drs usually don't jump up at a QTc of 440 to 470. They probably will sit up when they see 500msec and above several timesin a row on ECGs.
So, I hope it helps you somewhat to relax a little....but if you feel your fast heart rate is accompanied by dizziness, do go see your cardiologist soon. They maybe not the sinister sort cos there are many types of arrhythmias...but it's always good to check to allay your fears and set your mind at ease?
I have an ICD implanted for many years and taking beta blocker as well as arrhythmia meds to prevent untoward attacks. But I know I am always looking over my shoulder to make sure I won't have "rude shocks"!!
If you feel you want some assurance feel free to contact me.? I hope you feel better soon...good luck. God bless.
Also forgot to mention I have sinus arrhythmia...could that affect the accuracy of the QT measurement?
Thanks, that helped a bit. I always had an anxiety problem and that was my doctor's diagnosis for my problems, but reading about long QT has scared me. Any other answers welcome.
Hi TP92,
Heres the little I know about a long QT interval:
Yes the upper limit is in the mid 400s
It is caused by a few things but the two I remember are certain prescription medications and neurologic problems
It is not common
Most times Ive seen people have an issue with this, the QT interval is much higher than the low end of the abnormal range. For example a QT number in the upper 400s to low 500s
If it were me, I wouldnt be worried at all, especially since you asked your questions at your visit.
Maybe another forum friend can offer more info... but I do know I wouldnt worry. Hope this helps :)
Heres the little I know about a long QT interval:
Yes the upper limit is in the mid 400s
It is caused by a few things but the two I remember are certain prescription medications and neurologic problems
It is not common
Most times Ive seen people have an issue with this, the QT interval is much higher than the low end of the abnormal range. For example a QT number in the upper 400s to low 500s
If it were me, I wouldnt be worried at all, especially since you asked your questions at your visit.
Maybe another forum friend can offer more info... but I do know I wouldnt worry. Hope this helps :)
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