Calculate the corrected QT Interval using our free online QTC Calculator
QT interval is a measure of the time taken for the heart muscle to depolarize and then repolarize, representing electrical systole. It is a significant parameter in electrocardiography (ECG) studies. However, the QT interval can vary with heart rate, and therefore it is often corrected (QTc) to facilitate comparison between patients with different heart rates. This tutorial explores the Corrected QT Interval, its formula, and the fascinating facts surrounding it.
|QT Interval, QT
|Heart Rate, HR
|Corrected QT (QTc)
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The QT interval was first described by a British physiologist, Augustus D. Waller, in 1887 using a capillary electrometer. The term "QT" comes from the letters used to denote the start of the Q wave and the end of the T wave on an ECG. An abnormally long or short QT interval can predispose an individual to arrhythmias, a potentially life-threatening condition. Therefore, the correct interpretation of the QT interval holds significant clinical value.
The most commonly used formula to calculate the QTc is Bazett's formula:
Where QTc is the corrected QT interval, QT is the measured QT interval, and RR is the interval from the onset of one QRS complex to the onset of the next QRS complex, typically measured in seconds. RR interval is related to the heart rate and is often approximated by taking the inverse of the heart rate.
Beyond cardiology, the QT interval and its correct interpretation have relevance in fields such as pharmacology and genetics. In pharmacology, certain medications can cause QT prolongation, a potential side effect that requires careful monitoring. In genetics, specific genetic mutations can lead to Long QT Syndrome, a condition characterized by prolonged QT intervals and a risk of sudden death.
For instance, consider an ECG where the measured QT interval is 400 milliseconds, and the heart rate is 60 beats per minute. To find the QTc using Bazett's formula:
This value falls within the normal range for QTc (up to 440 ms for males and 460 ms for females).
Augustus D. Waller is credited with the first description of the QT interval, but it was Henry Cuthbert Bazett who devised the most popular formula for QT correction that is still in use today. Their contributions have been pivotal in understanding cardiac physiology and pathology, and continue to inform clinical practice, enhancing patient safety and care.
The Corrected QT Interval, its calculations, and implications are a cornerstone of modern cardiac electrophysiology, enabling clinicians to assess and manage cardiac arrhythmias effectively.
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Please note that the Corrected Qt Interval Calculator is provided for your personal use and designed to provide information and information relating to the calculations only. The Corrected Qt Interval Calculator should not be used for you to self-diagnose conditions, self-medicate or alter any existing medication that you are currently prescribed by your Doctor. If the Corrected Qt Interval Calculator produces a calculation which causes you concern, please consult your Doctor for support, advice and further information.