Was my adverse drug reaction due to my Borderline or Prolonged QT interval?
Posted , 5 users are following.
Drug Induced Long QT Syndrome (LQTS)
Long QT Syndrome ( LQTS) is a congenital electrical impairment of the heart, affecting about in one in 3000 people, which may present itself in up to 13 variants each having its own signature of morbidity (i.e. the way in which those with LQTS will probably die). It may not be observable in any mechanical investigations of the heart and a diagnosis can only be verified by genetic analysis with familial consent.
However, there are implications for people who may not be diagnosed as having LQTS but who have Borderline or Prolonged QT intervals, putting them at greater risk of cardiac events from certain classes of drugs that actually prolong their QT interval and mimic the effects of having LQTS. This is called Drug Induced Long QT Syndrome.
Since 2005, the FDA and European regulators have required that nearly all new drugs should be evaluated in what is called a Thorough QT (TQT) study to determine the drug’s influence on cardiac arrhythmias that can possibly lead to a fatal outcome.
Here is a table of QT intervals based on a heart rate of 60 beats per minute (QTc) in the absence of: drugs, electrolyte imbalance, ischemia and diurnal influences:
Male (HR=60 bps) Female (HR=60 bps)
Short QT 330 to 360 ms 340 to 370 ms
Normal QT 360 to 430 ms 370 to 450 ms
Borderline QT 430 to 450 ms 450 to 470 ms
Prolonged QT 450 to 500 ms 470 to 510 ms
Long QT Syndrome 390 to 600+ ms 400 to 600+ ms
This is an extended table based on European regulatory guidelines for QTc prolongation.
In view of these TQT drug evaluations, ways of improving the accuracy and interpretation of ECG waveforms with respect to manual reading and/or automated methods are in progress to minimise the occurrence of adverse drug reactions.
The question now arises as to the safety of drugs that pre-date the TQT evaluation requirements of 2005.
Any Comments?
0 likes, 8 replies
lyn1951 Bob37393
Posted
My husband has a very long QT interval, it is caused by a Left Branch Bundle Blockage, the local GP said it was nothing to worry about.
I wasn't happy about his opinion, something told me it was more than than, so demanded to see a cardiologist, GP said we were wasting our time.
I insisted.
About 10 days later saw a private cardio specialist, echocardiogram preformed, and that diagnosed what was really wrong.
Husband had dialated cardiomyopathy, cause unknown.
How did i know something was wrong, didn't occur to me until months later, my Dad had dialated cardiomyopathy his entire life, not diagnosed until he was in his late 60's, Dr's shocked at just how well he was, and that he had served in Egypt during WW2, they assume with the problem, he had rheumatic fever at 18 years of age, and they seemed to think that is where his problems orginated.
Back to husband, has since developed Right Branch Bundle Blockage, and has had pacemaker and defib installed about 2 weeks ago.
One thing they did mention was his tablets causing the problem, so took him off all his medication, he only got worse heartbeat dropped to 23 beats a minute, and internal hospital emergency flying team called to him twice over 24 hours.
After pacemaker installed, his health improved immiedately, and pain in his left arm vanished, the pain he had for months, and it had been dismissed as rotator cuff, muscle strain, x-rays, cat scans, all came back as clear.
I do think the pain may have been coming from his heart but very unusual, no other pain anywhere.
Bob37393 lyn1951
Posted
Your account illustrates how people can happily live with undiagnosed conditions yet be treated with medications for something else.
We should be concerned about the co-administation of medications where the undesirable effects of an earlier one are treated with another.
This may be OK until withdrawal from drugs is necessary, the consequences of which cannot be predicted by doctors.
I withdrew from polypharmacy against my doctor's advice and survived - I feel much better for it.
I should not have believed my GP when I felt healthy and fit yet I was deemed to have an illness that needed treatment.
lyn1951 Bob37393
Posted
I have made a point of if you want to give me and or my husband tablets you had also better give me the printout on said drugs that i will take home and study, pick apart and question.
One new tablet I was given by rheumo specialist seemed to be causing me blood pressure problems, really dangerously high.
GP denied it was a problem, I ended up arguing with GP about it, that it seemed to much of a coincidence that my BP had only gone so high since this new tablet had been introduced.
I then questioned chemist who prescribed, and he said there may be an issue as I had never had BP problems previous, and he was aware of that, I had never previously been prescribed BP tablets.
In the end rang the drug Co listed on the side of the bottle, and started asking questions, I explained what had been happening, that my BP was crazy high, and asked could it be the tablets.
Their reply was to ask me who my Dr GP was, I told them, about 30 minutes later got and abrupt phone call from GP telling me not to take any more of those arthiritis tablets, maybe they were causing the BP problem.
Would have loved to have been a fly on the wall when GP got that phone call, I was right in my opinion that it was the new tablets.
Educating myself in fact saved my life, or so I have since been told, I am a group of very rare reaction to that particular arthrits drug about 2% of patients, and not a happy outcome.
Same with my husband, I have been able to have his tablets adjusted so they are better for him, presented my opinion to specialist and he agreed with me, what really gets in my craw is he should have picked up on the change of tablets, not me, with no medical training, but pedantic research skills.
Also some other tablets that work for him, the specialist has been tring in the local heart hospital, just by chance found to work very well.
mac58 Bob37393
Posted
i have just been diagnosed with LQTS and I am not sure if it was always there, or drug-induced. I do know that various drugs I was taking have been stopped.
babs25 mac58
Posted
mac58 babs25
Posted
It was just a routine ECG at the doctor's surgery. she hasn't referred me on to a cardiologist - just stopped some of my medications.
babs25 mac58
Posted
Bob37393 mac58
Posted
There is however no defined QT interval at which a Long QT syndrome can be diagnosable.
Things are further complicated by the fact that many drugs are known to elongate QT so if you have an existing longer QT than average a drug may well put you at higher risk of developing heart rhythm problems.
It would be useful if you could establish your QT intervals when on one particular drug and then later after withdrawal under the supervision of a medical professional.
Note however that whilst modern drugs should be screened for QT elongation that is not the case for older drugs that predated the screening deadline.