Long QTc interval on ECG

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I’ve been flying for 25+ years with both military and FAA physical exams, to include a bunch of ECGs, the most recent one of which was in June. I had an urgent care visit about a week and a half ago where they did an ECG that showed a prolonged QTc interval. A follow up today at my family medicine physician showed the same, so now I’m self-grounding and have a cardiologist appointment in a couple of weeks. Just wondering if anybody here has dealt with something similar.
 
My June (normal) ECG showed QT of 409 ms and QTc of 442 ms.

My abnormal urgent care visit showed QT of 407, but due to a sky-high heart rate (I was very nervous about the reason I was in urgent care in the first place) and using the Bazett calculation, QTc was 529. A Framingham calculation would have shown about a 469 QTc, but my doc seemed kind of dismissive about that.
 
Just to throw it out there there, I can think of couple things have changed since my previous normal ECG:

In October I started simvastatin. I don’t think there’s a documented connection, but it is a change.

I’ve been diagnosed as subclinical hypothyroid before - in the past couple of months I’ve been cold when nobody else in my family is. I don’t have a current TSH number, but I’m wondering if that’s gone out to lunch. My doc told me that hyperthyroidism is connected with QT, but I see in multiple online sources including Mayo that hypothyroid has a QT prolongation connection.

I’ve been intermittent fasting since August. The good news is I’ve kept off about 10 pounds easily, but I’ve recently seen a single study linking fasting and lower blood sugar with a longer QT interval.

Just wanted to throw those out there and see if anything rings true to anyone else. I’ll definitely have my list of anything I can think of when I see the specialist.
 
Well above 500 the risk is torsades de pointes.
I'd start with: Are you doing any "health or workout" supplements?
If so, LOSE THEM ALL and after 2 weeks get another EKG.

B
 
Besides simvastatin, I was taking green tea extract, pomegranate extract, beet root extract and a multivitamin. Except for the simvastatin, I’ve now stopped those.

Any thoughts on the QT/QTc accuracy of an Apple Watch Ultra? I’m using the ECG+ app and in a controlled, calm situation my QTc bounces around the 410-440 range. I know it’s a single lead and a consumer product, but any opinion on accuracy?
 
Things to consider

1-You didn't mention if you drink alcohol. sometimes alcohol use can cause mag depletion and prolong the QT. If you drink, even socially, then quit the alcohol for the time being and push the fruits and veggies, especially high potassium and magnesium ones. There is a weak association with low TSH/Hashimoto's thyroiditis and lower levels of body magnesium, but whether this is clinically relevant is open for a lot of debate.

2-I'm assuming they did an electrolyte panel and mag, but you didn't explicitly say. You should have this checked if not already checked. Oh and try not to get anxious and tachycardia for your ekg with the cardiologist.;) I'm joking, but I'm not. Those calculators have varying levels of inaccuracy with very high heart rates. The closer you can get to a relatively normal resting rate in the 60's, the more accurate it will be.

3-the machine read of the QT/QTC interval can be incorrect. machine and manual interpretation of QT interval

Basically, do what Doc Bruce said and stop all supplements. Stop any alcohol as well. Push the potassium and magnesium rich fruits and vegetables. If you didn't get labs, get them from your cardiologist. Make sure you're nice and mellow, ie. you have a nice slow heart rate when you see him/her.

Hopefully the cardiologist's interpretation of the Qt will be normal or minimally elevated...

If after all this, your Qtc is over 500ms, well, that is interesting. (And, as I used to tell my patients, "you never want the doctor to say something is interesting about your medical history." You want to be boring to the doc...).

Still, I'm willing to bet that, if your labs are normal, you don't drink, your diet has lots of dietary mag and potassium, and your heart rate is reasonable, then you won't be interesting to the cardiologist...

Good luck
 
PS, there is some data that the Apple Watch can measure Qt's with reasonable accuracy, but it wouldn't be considered the gold standard. So it's reassuring that your Apple Watch Qtc look good, but you're still just stuck getting everything sorted out...
 
Mark,

Thanks for the info. My last electrolyte check was done in August. My sodium and potassium were at the low end of normal, but I’d just been running beforehand. Unfortunately I don’t have more current data, but I’m literally eating an avocado as I type this. I’ve had no alcohol and no caffeine since this mess started, but have previously drank in moderation and often had more than my fair share of coffee.

I finally got the numbers from my follow up ECG that was a couple of days ago. Again, I was very nervous (I’m an awful white coat patient) so my HR went from 75 in the car to over 100 on the ECG table. The QT itself wasn’t awful and the QTc with the Bazett formula was still elevated but about 480. If they had used the Frederica, Hodges, Framingham, or Rautaharju formulas the QTc would have been less than 450.

When I look at the trends from the Apple Watch, the overall arc seems to show the QTc and HR averaging down on both since I started looking at this just before Christmas. I don’t know if that’s me getting calmer with the app or eliminating supplements or something else entirely is having an effect.

I hope to be the calmest, most boring patient I can be at the cardio.
 
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