Talk:QT interval

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There is some confusion in the first paragraph of this article. The phrase "The QT interval is dependent of the heart rate" is confusing. The word "independent" is generally followed by "of" but the word "dependent" is generally followed by the word "on". Unfortunately, I do not have time right now to check this fact to find out which word to change.--Heritagecoinshop 23:32, 24 May 2006 (UTC)

EKG graphic desired

It would be nice to have an EKG graphic showing what part this QT interval is. It would even help give the lay person some idea of what it is (most people have seen EKG graphics already).

Done --WS 10:48, 9 July 2006 (UTC)

QTcF not frequently used?

I'd like to see a citation on this. Not that I don't believe it, but I've definitely seen it used as the measure of choice when other correction methods are available. –Scott182 01:36, 6 June 2007 (UTC)

Abbreviations QTc vs. QTF?

I'm confused by the left-hand side of the two formulas. I thought that it was "QTcB" for the Bazett formula, and "QTcF" for the Fridericia formula. Can somebody more knowledgeable comment or amend? (212.203.114.194 18:12, 12 November 2007 (UTC))

acesibiliti

blakbakground>diagramilegibl:((81.11.207.108 (talk) 17:37, 3 April 2016 (UTC)

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Request citation?

In the formulas, is “QT” measured in seconds or in milliseconds? Also, where the second paragraph of this article says that the QT correction printed by an EKG machine “may not aid in the detection of patients at increased risk of arrhythmia,” why not? I edited the paragraph based on the assumption that the reason this correction may not be useful is there are different formulæ, and if the machine uses the wrong one then it may not be helpful. If my edit was inaccurate or incorrect, then please revert me. 2600:1003:B015:319D:0:50:8948:D601 (talk) 16:35, 8 August 2016 (UTC)

What about antipsychotics affecting QT interval.

It's a well known side effect but not reported in the article. 2A02:587:390C:DE00:D024:12DB:453:5344 (talk) 10:32, 12 May 2020 (UTC)

The Abnormal intervals section due to adverse drug reactions subsection mentions haloperidol, an antipsychotic, and directs the reader to a more complete discussion at the Drug-induced QT prolongation page. PeaBrainC (talk) 16:42, 12 May 2020 (UTC)

The second sentence bothers me, multiple problems

Currently, the second sentence in the lede section says this:

"[the QT interval] approximates to the time taken from when the cardiac ventricles start to contract to when they finish relaxing"

The verb "relaxing" is especially problematic, because as an electrical measurement (as opposed to the metrics available during echocardiography, which can measure end diastolic volume), the QT interval reflects the flow of ions, and it doesn't differentiate between sodium, potassium, and chloride ions. Chloride ions most closely correlate with myocardial contraction and relaxation, but the outward flow of potassium ions (and decreased or near-zero inward flow of sodium) is probably mostly what generates the T wave.

The myocardium is arguably more relaxed (larger ventricular volume, longer muscle fibers) even later in the cycle, after the end of the T wave.

The QT interval more closely shows when the ventricles finish repolarizing, not when they are relaxed. But I am reluctant to modify the lede section significantly to talk about action potentials.

Repolarization is clinically important because cardiomyocytes that have not yet repolarized are very likely still in the refractory period, although the status of sodium channels as well as the membrane potential determine whether the muscle is excitable or refractory.

It is the electrical properties of the heart, such whether it is refractory and conduction velocity, that determine whether reentry can occur within the ventricles, leading to ventricular tachycardia, generally TdP in the case of long QT intervals.

QT interval has everything to do with action potentials and I am tempted to overhaul the lede section, saying that the T wave shows the ventricles "relaxing" is basically a red herring, myocardial relaxation relates more to heart failure and not ventricular tachycardia.209.94.144.13 (talk) 03:10, 22 May 2021 (UTC)