Qtc Calculator

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How QTc Calculator Works?

The online QTc interval calculator will be able to correct the QT interval for the heart rate of your patient.


What's the meaning of normal QTc?

QTc intervals are typically 350–450 milliseconds in men and 360–460 milliseconds in women. It is the difference between the shortest and longest QT intervals on a normal ECG that is known as QTc.

When should the Fridericia formula be used?

Cancer patients who are exposed to potentially QT-prolonging cancer therapy should use the Fridericia or Framingham formula for the measurement of QTc, which better reflects a real corrected QT interval.

What's the distinction between QT and QTc?

For the most part, QT intervals are normalized for pulse rate so that QTc is equal to QT if the pulse rate is 60 beats per minute, resulting in 1 second of RR interval for the patient.

What is the QT syndrome?

Because the QT interval shortening implies the heart has less time to recharge and rest between beats, this disease can induce arrhythmia, which is a disruption in the heart's normal rhythm. However, there is no underlying anatomical abnormality of the heart.

What happens if the QT is significantly higher than normal?

Arrhythmias include the long QT syndrome, which is a rare but potentially dangerous disorder in which the heart's electrical activity is interrupted. The QT interval is prolonged in some people but they don't have a significant arrhythmia, whereas, in others, the heart beats faster for no apparent reason, resulting in a lack of oxygenation to the brain, which causes fainting.

Beginners Guide of QTC

The QTc calculator allows you to do a correction of the QT interval for your patient's heart rate using the information provided in the calculator. Bazett formula and other equations will be used to determine QTc in the following section (e.g., Fridericia, Framingham). The hazards of QT prolongation are discussed, as well as which QT-prolonging medications should be avoided when treating individuals with an abnormally long QT interval.
It is important to keep in mind that this QTc correction calculator is not a substitute for a consultation with a medical professional. Make an appointment with your doctor if you're concerned about the results you received.

What is QT Interval?

Interval QT represents the heart's electrical function on an electrocardiogram (ECG). Beginning with the depolarization of the ventricles, the QRS complex progresses to the end of the T wave (the repolarization of ventricles).
Cardiologists frequently check the QT interval because it is associated with ventricular arrhythmias such as torsades de pointes and increases the risk of sudden cardiac death. The more rapid your heartbeats are, the shorter your QT interval will get. As a result, an adjustment to the QT interval for heart rate is necessary. It's possible to use a Bazett formula for it.

Bazett Formula

An article published in the Heart Journal in 1920 by physiologist Henry Cuthbert Bazett, titled "An Analysis of the Time-Relations of Electrocardiograms," contains the most widely used equation for QT interval adjustment. Using the following steps, we can arrive at Bazett's formula:
QTc = QT / √RR,
QTc = QT (corrected)
QT = QT interval length
RR = RR (duration)
However, despite its widespread use, Bazett's formula has some drawbacks. For example, it is notorious for overcorrecting at high heart rates while undercorrecting at low heart rates.
There have been a number of alternative equations put forth, including:

You may wish to examine any medication to see whether it has an effect on the QTc interval.

There are a number of medications that can cause an increase in the QT interval as a side effect. A variety of medications, including antiarrhythmics such as amiodarone and sotalol, antibiotics such as quinolones (levofloxacin) and macrolides (erythromycin), psychiatric and antihistamines medications, can cause it.
A risk-benefit analysis should be undertaken before adding a QT-prolonging medication to a patient's treatment plan, especially when other risk factors are present.

Abnormal QT Intervals Causes

During the late depolarization phase, prolonged QTc increases the risk of premature action. This raises the chance of catastrophic ventricular fibrillation, as well as ventricular arrhythmias. Women and the elderly are more likely to have high blood pressure or heart rate, small stature, and longer QTc.
ECG abnormalities known as Torsades de Pointes are also related to extended QTc values, which can degenerate into ventricular fibrillation, which has a greater fatality rate. Genetic causes of prolonged QT intervals are not the only ones that might lead to this problem.

1. Genetic Reasons

Variations in the NOS1AP gene are linked to QTc length. A long QT syndrome can result in an abnormally long QT interval, while a short QT syndrome can result in an abnormally short QT interval. With the sensory hearing loss in Jervell and Lange-Nielsen syndrome, a lengthy QTc interval is also present.

2. Mortality Predictor

An electrocardiogram can be used to spot persons at increased risk of dying because it is noninvasive and painless. Overall, there was no indication that a longer QTc interval was linked to an increased risk of mortality from a cardiovascular illness in the general population. On the other hand, multiple studies indicated that abnormalities in the QT interval were associated with a higher risk of death in sick populations.

3. Adverse Drug Reactions

The QT interval can be extended as a result of medication interactions. The QT interval can be lengthened by a number of drugs, including ziprasidone, methadone, haloperidol, vemurafenib, and sertindole. Pharmaceutical QT prolongation is achieved by medications like sotalol and amiodarone (used as antiarrhythmics).
Second-generation antihistamines such as astemizole have the same effect. Furthermore, the QTc measurement is longer when blood alcohol contents are high. Taking selective serotonin reuptake inhibitors plus thiazide medications may cause an increase in the QT interval. After azithromycin was recently shown to be connected to an increase in cardiovascular death, there is little question that macrolide antibiotics stretch the QT interval.

4. Psychiatric Disorders

QT prolongation can be caused by hypothyroidism, a condition in which the thyroid gland is underactive. Acute hypocalcemia can cause cardiac dysrhythmia by lengthening the QT interval. Hypercalcemia has been linked to a shortened QT interval.

5. Rheumatoid Arthritis

There are many different types of inflammatory arthritis, but rheumatoid arthritis is the most common. Rheumatoid arthritis has been linked to an increased risk of cardiovascular disease mortality. QTc intervals of less than 424 milliseconds (ms) were shown to have the lowest mortality rates in a study by Panoulas and colleagues in 2014.
When the C-reactive protein level was recalculated, the connection was broken. An elevated QTc period and arrhythmias were linked to a greater death rate by the researchers. Exactly how C-reactive protein and the QTc interval are connected remains a mystery.

6. Diabetic type 1

Diabetics with type 1 diabetes have a higher mortality risk than those in the general population. A QTc interval abnormality (> 440 ms) is found in nearly half of patients with type 1 diabetes. Diabetes with a prolonged QTc interval has been linked to 29% of deaths. To put this in perspective, the QTc interval has a mortality rate of 19%. QTc prolongation caused by antihypertensive medications has not been associated with an increased risk of death.


An online QTc calculator can be utilized to adjust the QT interval for the patient's heart rate. QTc can be calculated using Bazett's formula and other equations in the following paragraphs. Long QT or QTc intervals indicate improper myocardial effects. Congenital and acquired QT prolongation are the most common types of QT prolongation. A genetic condition known as congenital QT prolongation increases the risk of sudden death in children and young adults. Hemorrhagic shock, electrolyte abnormalities, cardiac valve ablation, or medicine can all cause QTc prolongation.