Fig. 1. Assessment of the 24-hr QT dynamics in healthy male aged 22 using the modern Holter monitoring system. QT/RR slope (QTо) = 0.199

Fig. 2. Ventricular tachyarrhythmia that occurs at 05:44 am, ventricular fibrillation and sudden death that occur at 05:56 am in female patient aged 77 with ischemic cardiomyopathy and ejection fraction of 38%. No option for assessment of QT dynamics was installed in the system

Fig. 3. Nocturnal heart rate trend with sudden death occurring at 05:56 am (see Fig. 1) during the period of the increased heart rate variability that corresponds to REM sleep phase according to conventional somnography [8, 13] in the 77-year old female patient with ischemic cardiomyopathy

Fig. 4. QT hyperadaptation in male patient with type 3 long QT syndrome. QT/RR slope (QTо) = 0.369 (normal range: 0.13–0.24)