For accurate measurement of QT interval measurement, the relationship between QT and the R–R
intervals should be reproduciblerepeatable, particularly in cases with. This aissue is important when theheart rate of < 50 bpm and >120 bpm. Moreover, Accurate measurement of the QT interval is also

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important in athletes and children who have a significant beat-to-beat variability of the R–R interval may
need . In such cases, prolonged and numerous recordings for accuracymay be necessary. The
longestLongest QT interval is generally observed in the right precordial leads.

Long QT syndrome (LQTS) is a congenital disorder characterized by, which shows a protracted QTinterval on the electrocardiogramECG. This condition predisposes patients to the development of Thiscondition influences ventricular tachyarrhythmiatachyarrhythmias to develop in people, which may lead tosyncope, cardiac arrest, or sudden cardiac death. AdditionallyIn LQTS, QT prolongation can lead topolymorphic ventricular tachycardia, which is also referred to as torsade de pointes, which in. Thiscondition itself may result inlead to ventricular fibrillation and sudden cardiac death.

Considerably, torsadeTorsade de pointes is widely thought to be triggered by calcium channel
reactivation, a delayed sodium current reactivation, or a diminished outward potassium current that resultsin early afterdepolarization (EAD). This leads to enhanced transmural dispersion of repolarization (TDR)

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defined at its first use in the text and the abbreviatedform is consistently used thereafter.

and is usually associated with a prolonged QT interval. TDR serves as a functional reentry background tomaintain torsade de pointes. TDR It provides a reentry background for reentry and increases the risk
likelihood of EAD, the trigger for torsade de pointes, by extending the extension of the time window for
calcium channels to remain open. Any additional further condition that acceleratesing the reactivation of
calcium channels reactivation (e.g., increased sympathetic tone), increases the risk of EAD.

Prolonged recovery from excitation increases the probability chance of dispersion of refractorinessdispersion, when some parts of the myocardium are refractory to subsequent depolarization. From aAll material in this document is the intellectual property of Crimson Interactive Pvt. Ltd. The use of information and content inthis document in whole or in part is forbidden unless express permission has been given in writing by Crimson Interactive Pvt.
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physiological viewpoint, dispersion occurs with repolarization betweenof the three layers of the heart, andthe repolarization phase tends to be prolonged in the myocardium. This is the reasonTherefore, why the T
wave is usually wide and the interval from the peak of the T -wave to its end (Tp-e) represents thetransmural dispersion of repolarization (TDR). In long QT syndrome (LQTS), TDR increases and createsa functional background for transmural reentry.

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Ltd.

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