VZL 2007, 76(3):83-88

Regression Equations for Electrocardiographic QT Interval of Children and Adults

Štefan Kujaník
Ústav fyziológie Lekárskej fakulty Univerzity P. J. Šafárika v Košiciach, Slovenská republika

Jedným z ukazovateľov elektrickej stability srdca je aj trvanie intervalu QT (elektrickej systoly). Závisí na srdcovej frekvencii, pri tachykardii sa skracuje, pri bradykardii predlžuje. Jeho hranice na EKG však nie sú veľmi presne definované, najmä koniec vlny T. Pre trvanie QT sú dôležité hlavne komorové bunky typu M, ktoré majú veľmi dlhé akčné potenciály. Bol navrhnutý veľký počet regresných rovníc pre interval QT, lineárnych aj nelineárnych. Trvanie QT aj matematický vzorec regresnej rovnice závisí od niekoľkých faktorov - srdcová frekvencia (RR), pohlavie, vek, telesná námaha, ochorenia, lieky. Trvanie QT u zdravých žien je pri rovnakej frekvencii srdca asi o 10-20 ms dlhšie ako u zdravých mužov, u starších ľudí je dlhší ako u mladších. Príčinou pohlavného rozdielu je spomalená repolarizácia komorových buniek u žien. Mnohé kardiovaskulárne, mozgové, iné ochorenia a niektoré lieky môžu predlžovať interval QT. Zmena závislosti trvania intervalu QT od srdcovej frekvencie znamená zmenu aktivity autonómneho nervového systému. Vzťah intervalov QT a RR je značne individuálny a špecifický pre každého človeka.

Keywords: Elektrokardiografia; QT interval; Srdcová frekvencia; RR interval; Regresné rovnice

One of the parametres of the electrical heart stability is also the QT interval (electrical systole) duration. It depends on the heart rate, during tachycardia it is being shortened during bradycardia it is being prolonged. However, its limits on the ECG are not very exactly defined, especially the end of T wave. For QT interval duration the ventricular cells of type M are mainly important and they have the very long action potentials. Plenty of equations were proposed, linear or nonlinear. QT duration and the mathematic formula of regression equation depend on several factors - gender, age, exercise, diseases, pharmacological agents. QT duration in healthy women at the same heart rate is approximately by 10-20 ms longer than in healthy men, in elderly persons is longer than in younger ones. The slowed repolarization of ventricular cells in women is the cause of the difference. Many cardiovascular, cerebral, other diseases and some drugs are able to prolong QT interval. Change of the dependence of QT duration on the heart rate means a change of autonomic nervous system activity. Relation between QT and RR intervals is highly individual and specific in every person.

Keywords: Electrocardiography; QT interval; Heart rate; RR interval; Regression equations

Received: December 14, 2006; Published: September 1, 2007  Show citation

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Kujaník, Š. (2007). Regression Equations for Electrocardiographic QT Interval of Children and Adults. Vojenské Zdravotnické Listy, 76(3), 83-88
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