QT interval duration at a stable heart rate of 60 bpm is a new assessment parameter for Holter monitoring

The relevance of the study is due to the limitations in the calculation and evaluation of the corrected QT interval (QTc) in patients with Holter monitoring (Holter ECG).

Aim: to formulate an algorithm for determining the duration of the QT interval at a stable heart rate of 60 beats per minute during Holter monitoring, and to determine its advantages and limitations.

Material and research methods. The study included 90 patients, the average age of which was 54,48±14,8 (M±σ) years, including 42 men and 48 women, who underwent Holter ECG for 24 hours.

Research results. The developed method for measuring QT60 consists of the fact that during post-processing of daily Holter ECG data, a stable heart rhythm with a heart rate of 60±3 beats per minute is found, at the end of a 10-second period of which the QT value is measured, which is the QT60 interval. The closest in value to QT60 was the Sagie method (p=0.386), while the Bazett and Fridericia formulas showed reliable differences from QT60. The average values of QTc scatter during the entire registration period, calculated by the Sagie formula (QTсS), are statistically significantly less than the scatter of values by Bazett and Fridericia, which shows the best stability of QTсS to changes in heart rate.

Conclusion. 1. The proposed QT60 parameter is free from the disadvantages associated with the use of various calculation formulas and does not require the use of automatic analysis, which leads to significant errors, especially when the patient has various rhythm disturbances, and we propose using the QT60 value as an additional parameter for assessing the QT interval in clinical practice. 2. If it is not possible to find a stable heart rhythm with a heart rate of 60 beats per minute during Holter ECG, we recommend evaluating the average daily QTc value calculated using the Sagie formula.

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