What should you do if one EKG out of several shows a prolonged QTc interval?

Your cardiologist may then start talking about possible cardiac arrest.

This is scary sh**! And I know this because it happened to me.

I visited the cardiologist for the fourth time (in five years) for a routine checkup. I asked how it was and the doctor casually mentioned that the QT interval was prolonged.

He wanted me to have blood drawn to see if I had an electrolyte deficiency, which he thought might have been from nutritional supplements.

He asked if I had ever fainted. I told him absolutely never (the truth). He explained that a prolonged QT interval could lead to ventricular fibrillation and possibly sudden cardiac death.

“When an EKG is used to diagnose LQTS, one must NEVER use the machine’s calculations alone, but use a manual calculation by an experienced cardiologist with expertise in diagnosing the condition,” explains Teri Dreher, RN, CCRN, an award-winning RN patient advocate and pioneer in the field of private patient advocate.

Dreher, a critical care nurse for 30+ years, is owner/founder of NShore Patient Advocates in Chicago. She is also a former cardiovascular nurse clinician for Wisconsin Heart and Vascular.

At home I looked at the QTc: 488, and at the top of the printout it said: borderline extended QT interval.

An online search revealed that the “borderline” range for women is 440 to 470 (some sources said 440 to 460).

One EKG Shows Borderline Prolonged QT Interval

Online I learned there are two kinds of long QT syndrome: genetic and acquired.

Next day the blood work results came back: The potassium, magnesium and calcium levels were normal!

I immediately arranged to have a repeat EKG later that day and with a different nurse this time.

By the time I had made the appointment, however, my fears had begun to subside; the more I learned about this intriguing condition, the more I realized I couldn’t possibly have the genetic form.

And I certainly didn’t have the acquired. I was on no medications and did not have diabetes, congestive heart failure or low thyroid—conditions that can lead to LQTS.

The EKG next day showed a QTc of 458. I told the nurse that the first nurse had placed an EKG lead near each foot.

She said this could have thrown off the reading. She said, “Ever hear of operator error?”

I asked her to retrieve the QTc readings of the EKGs from my previous three visits with the cardiologist.

All three QTcs were in the high 450s, and none of these printouts flagged these readings.

According to what I had read online, high 450s is in the “borderline” prolonged range for women.

However, there’d been no flagging for the previous three visits to the cardiologist. So according to Kaiser Permanente’s system, high 450s is normal.

The calculation is done by computer, and if it’s high enough, the computer spits out that “borderline extended QT interval” on the EKG paper.

“Machines are fraught with errors, and physicians often misdiagnose also,” says Dreher.

“One study showed that up to three-fourths of cardiologists make errors in measurements.

“Artifact, heart rate abnormalities, T wave and u wave changes will also affect a proper measurement.”

After I got the repeat EKG, my cardiologist sent me the following message:

Hi, like a lot of things in medicine QT intervals vary and we don’t always know why, although I’m glad it’s better.

There are some folks with long QT syndromes who don’t have a long QT on every ecg but the fact that most of yours look good is reassuring.

It’s possible that technical factors could explain the variation. In addition QT is hard to measure and in my experience there is considerable variation between docs regarding measurement – some leads look different than others and in some patients the end of the QT (depending on the slope of the waveform) is not clear cut.

How to Ease Panic if One EKG Shows Prolonged QT Interval

• How old are you? Do you have a lot of living behind you? This counts! Had this occurred to me at, say, age 15, I’d be panicking, because by the time you’re 15…how many times have you ever STRENUOUSLY exercised?

Dreamstime.com, Christopher Nuzzaco

• Sure, by the time I was 15, I had played volleyball and did jogging and bike riding.

But this was nothing compared to the grueling, intense physical exertion that was to come when I was older.

• The more years you have behind you of strenuous, heart pounding exercise, without any incidents of fainting, let alone cardiac arrest…the less likely you have genetic LQTS.

I told myself, “If I’ve had long QT syndrome this entire time since birth…my body has obviously coped very well with it, as I have experienced enough kickass workouts to induce thousands of cardiac arrests if I truly had LQTS!”

• For 35 years I’ve done high intensity interval training, crushing weight workouts, hill dashing, moving furniture, shoveling snow, martial arts, parking lot sprints, sled pushing…all-day hikes…plenty of opportunity to induce the LQTS-driven torsades de pointes!

Torsades de pointes. CardioNetworks/[CC BY-SA 3.0

Adding to my reassurance was the zero fainting episodes in immediate and extended family members, and zero unexplained or sudden deaths in them.

People with genetic long QT syndrome typically have family members with these features.

Long QT Syndrome on just One EKG: Bottom Line

“The bottom line is that there is too much public concern over the significance of abnormal QT measurements as stated on the electrocardiogram,” says Dreher.

“LQTS is a serious condition that should only be diagnosed by an expert, never by a machine, and cause for alarm should be mitigated by cautious healthcare practitioners.

“If the validated QTc is over 480 and verified by proper measurement, then a referral to an expert in LQTS treatment is judicious.”

Do not let that one EKG with the prolonged QTc interval freak you out. It is but one data point that needs to be considered within a bigger context.

Teri Dreher’s 35+ years of experience combines critical care nursing, home based healthcare and cardiovascular clinical nursing.
Lorra Garrick has been covering medical, fitness and cybersecurity topics for many years, having written thousands of articles for print magazines and websites, including as a ghostwriter. She’s also a former ACE-certified personal trainer.  


Top image: Shutterstock/TippaPatt