How important should the risk of qt prolongation be?

[cfsJapan]

I suffer from ADHD and CFS, but both are cured completely when I take tricyclic antidepressants (especially Nortriptyline).

However, the problem is that when I take them continuously, even at 5mg to 10mg, my QTc extends to 0.450 to 0.500 (my Qtc without Nortriptyline is about 0.410).

I also have tachycardia and my resting heart rate is 90 to 120 (strangely, my heart rate is lower after exercise than when I'm resting).

When I used Nortriptyline for 10 days in a row, I experienced symptoms similar to a heart attack (a strong feeling of pressure on the lower left side of my heart, a dull pain, a feeling I'd never felt before), and was taken to the hospital by ambulance, but they said there was nothing wrong with my heart. (It seems they treated it as a panic attack.)

You might say, "Then just don't take tricyclic antidepressants," but I can't function socially at all without Nortriptyline. Because of that, I was bedridden and shut-in for almost seven years.

You might be thinking, "Ask your doctor about that," but my doctor thinks there's no problem as long as it's not over 0.500. I think this is a little too optimistic.

I'm thinking of taking potassium and magnesium to prevent Qt prolongation, although it may only be a small help.

To sum up,

①At what level should Qt prolongation be taken seriously? Is 0.450-0.500 a clinically acceptable value?

②Are there any measures I can take to prevent Qt prolongation and sudden death that comes with it? (Like taking potassium)

I have a question about this score. Thank you for reading this far.

 

[bad1080]

from what i understand (which is very basic) the mechanisms of the heartbeat are quite delicate and the q time is an indicator for a correctly executed heartbeat. if the q time gets too long the heart does one thing before the other -in the incorrect order- which is a problem in a finely tuned and vital organ. this could be what you describe as "symptoms similar to a heart attack".
the tachycardia could be a way for the heart to deal with this prolongation but that's pure speculation on my part.

 

[katabasis]

I've heard a lot of doctors say that QT prolongation is not an especially serious phenomenon if <500 ms and with no other risk factors for sudden cardiac death. A cursory look at the literature shows that QT prolongation in general only has a relative risk of 2-3 in causing SCD (i.e. it's 2-3x more likely than for people who don't have QT prolongation). But unless you're elderly, the baseline rate of SCD is pretty low - it's only 0.3% over a 20 year period from ages 25-44 in the USA, according to this study. Personally, I'd be okay with increasing my odds of SCD from 0.3% to 1% in the next 20 years if it meant I could take a medication which would significantly improve my CFS.

Of course, it's important to look at your particular situation as well. Do you have any other risk factors for SCD? Diabetes, cardiovascular disease, etc.? Arguably, if you're deconditioned due to the CFS that might come into play. But then again, your QT prolongation is <500 so the relative risk is probably lower than the usual 2-3. There's no way to absolutely avoid risk, so I wouldn't get hung up if you do your own assessment and come to a similar conclusion about your level of risk. Just be sure not to take any other drugs that prolong QT interval, as they may have an unexpected multiplicative effect.

 

[bad1080]

Personally, I'd be okay with increasing my odds of SCD from 0.3% to 1% in the next 20 years

that is under the assumption the effects from the tricyclic antidepressants aren't cumulative. assuming they are would be the reasonable thing imo which is why they take you off them once the prolongation gets out of hand.
the amount of health anxiety tachycardia gave me would make this approach not worth it to me personally (and i had no heart attack-like symptoms).