Yu.E. TEREGULOV^1,2, L.F. SALYAMOVA¹, N.V. MAKSUMOVA¹, A.F. GIZATULLINA³

¹KSMA – Branch Campus of the FSBEI FPE RMACPE MOH Russia , 36 Butlerov Str., Kazan, Russian Federation, 420012

²Kazan State Medical University, 49 Butlerov Str., Kazan, Russian Federation, 420012

³Center of Sports Training of the Ministry of Youth and Sports of the Republic of Tatarstan, 58 H. Taktash Str., 420107

 Contact:

Teregulov Yu.E. — D. Med. Sc., Associate Professor, Head of the Department of Functional Diagnostics, Associate Professor of the Department of Hospital Therapy, tel. +7-917-264-70-04, e-mail: tereg2@mail.ru

Salyamova L.F. – Assistant Lecturer of the Department of Functional Diagnostics, tel. +7-903-342-34-13, e-mail: lilia.salyamova@mail.ru

Maksumova N.V. ― Assistant Lecturer of the Department of Functional Diagnostics, tel. +7-917-257-80-03, e-mail: nv_maks@mail.ru

Gizatullina A.F. – doctor of functional diagnostics, tel. +7-987-404-29-74, e-mail: bonheur_17@bk.ru

Nowadays sudden cardiac death (SCD) is an urgent problem all over the world. One of the important reasons of SCD is the change in the QT-interval duration, both its elongation and shortening. It is known that the QT interval depends on the heart rate. That is why it is possible to compare the QT intervals, corrected according to certain formulas.

There are many factors that cause syncope in patients with a long QT interval syndrome (LQT). Physical activity is the cause of syncope in almost 50% of cases. A number of authors suggest using a physical exercise test to diagnose LQT and a short QT interval syndrome (SQT) in patients with undetermined values of QTc (341-369 msec and 440-479 msec) [10, 11].

The objective of this study is a comparative analysis of various formulas for calculating the QTc interval during stress test. 47 healthy patients were examined (24 men and 23 women), mean age 47.9 ± 9.7 (M ± σ) years, men — 44 ± 13.2 y.o. and women — 46 ± 8.8 y.o.. All patients passed a stress test (treadmill test).

Regression linear analysis was used to study the dependence of the absolute interval QT and its corrected values (QTc), on the RR interval during stress test.

It is shown that the most exact methods of calculating QTc during stress test were Sagie (100%) and Fridericia (91.5%) formulas. The accuracy of Hodges and Karjalainen formulas was less than 20%. The accuracy of the most popular Bazett method was 44.7%.

Сonclusions:

1. Optimal formulas for counting the corrected QT interval during stress tests are Fridericia (91.5%) and Sagie (100%) formulas, while Bazett, Hodges and Karjalainen formulas are not correct in case of increasing heart rate.
2. The dependence of absolute and corrected QT values on the heart rate does not have gender differences.

Key words: long QT syndrome, short QT syndrome, calculation of corrected QT interval, stress tests, sudden cardiac death.

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