creators_name: Beata, Sredniawa creators_name: Agata, Musialik-Lydka creators_name: Piotr, Jarski creators_name: Anna, Sliwinska creators_name: Zbigniew, Kalarus editors_name: Singh, Balbir editors_name: Lokhandwala, Yash editors_name: Francis, Johnson editors_name: Gupta, Anup type: journalp datestamp: 2005-07-13 lastmod: 2011-03-11 08:56:07 metadata_visibility: show title: Methods of Assessment and Clinical Relevance of QT Dynamics ispublished: pub subjects: ipej full_text_status: public keywords: QT interval; ventricular repolarisation; QT dynamics; arrhythmic risk; QT interval prolongation abstract: The dependence on heart rate of the QT interval has been investigated for many years and several mathematical formulae have been proposed to describe the QT interval/heart rate (or QT interval/RR interval) relationship. While the most popular is Bazett’s formula, it overcorrects the QT interval at high heart rates and under-corrects it at slow heart rates. This formulae and many others similar ones, do not accurately describe the natural behaviour of the QT interval. The QT interval/RR interval relationship is generally described as QT dynamics. In recent years, several methods of its assessment have been proposed, the most popular of which is linear regression. An increased steepness of the linear QT/RR slope correlates with the risk of arrhythmic death following myocardial infarction. It has also been demonstrated that the QT interval adapts to heart rate changes with a delay (QT hysteresis) and that QT dynamics parameters vary over time. New methods of QT dynamics assessment that take into account these phenomena have been proposed. Using these methods, changes in QT dynamics have been observed in patients with advanced heart failure, and during morning hours in patients with ischemic heart disease and history of cardiac arrest. 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