A. Musialik-Lydka

Circadian and Sex-Dependent QT Dynamics

The dynamic QT relationship between the QT and RR intervals in normal individuals, including sex differences, has not been well examined. The aim of this Holter monitor‐based study was to assess circadian and sex‐related variations in QT dynamics in healthy subjects. The study population consisted of 50 healthy volunteers (mean age = 32 ± 6 years, 25 men), in whom 24‐hour digital Holter monitoring and QT interactive, beat‐by‐beat analyses were performed. The mean lengths of QT and RR intervals were measured from the 24‐hour recordings. In order to assess QT dynamics, QT/RR linear regression was performed, and the slope was calculated over 24 hour and for day and night periods, and both genders separately. In the whole population, the mean QT interval was 356.5 ± 19.2 ms and RR interval was 785.9 ± 80.7 ms. The mean value of the slope over 24 hour was 0.17 ± 0.03, though significantly steeper during the day (0.13 ± 0.03) than at night (0.09 ± 0.03, P < 0.001). The analysis of QT/RR dynamics over 24 hour revealed a significantly steeper slope in women (0.18 ± 0.03) than in men (0.16 ± 0.03, P = 0.006), as well as during daytime (0.14 ± 0.03 vs 0.12 ± 0.03, P = 0.04). Circadian variations and sex differences were observed in QT dynamics. The latter may explain the greater susceptibility of women to torsades de pointes during treatment with drugs that prolong repolarization.

Sleep apnoea as a predictor of mid- and long-term outcome in patients undergoing cardiac resynchronization therapy

AIMS To assess the impact of baseline apnoea-hypopnoea index (AHI) on mid-term outcome and its change after 6 months of cardiac resynchronization therapy (CRT) on remote outcome. METHODS AND RESULTS In 71 patients with CRT devices, Holter-derived AHI was assessed before and 6 months after the procedure. Baseline AHI >20 was considered abnormal. After 6 months of CRT, a 50% decrease of baseline AHI was considered significant and stratified patients into AHI dippers and non-dippers, except those who preserved normal AHI. Prognostic value of baseline AHI and its change were assessed in relation to mortality and major cardiac events (MACE). More patients with an abnormal AHI died during 6 months follow-up (P = 0.02), especially due to sudden cardiac death. MACE-rate was insignificantly higher in abnormal AHI patients. Significantly higher mortality (P = 0.001), especially due to heart failure progression and higher MACE-rate (P < 0.001) during further observation were observed in AHI non-dippers. In multivariate analysis, the absence of AHI reduction was an independent predictor of mortality [hazard ratio (HR) 6.56, P = 0.015)] and MACE (HR 6.05, P = 0.002). CONCLUSIONS Abnormal baseline AHI identifies patients prone to death during mid-term observation. Lack of AHI reduction after 6 months of CRT is an independent risk factor of death and MACE during further follow-up.

The significance of heart rate turbulence in predicting major cardiovascular events in patients after myocardial infarction treated invasively.

Introduction: The role of heart rate turbulence (HRT) related to baroreflex sensitivity in predicting mortality after myocardial infarction (MI) has been confirmed by several investigators. However, the significance of HRT in predicting major adverse cardiovascular events (MACE) following acute MI is unknown.

Effects of cardiac resynchronization therapy on heart rate turbulence.

Background: Cardiac resynchronization therapy (CRT) improves the clinical status of patients with heart failure (HF), though its effects on heart rate turbulence (HRT) are unknown.

QT dynamics and the risk of sudden arrhythmic cardiac death in ischemic heart disease.

The relationship between altered QT dynamics and the risk of sudden arrhythmic death has not been established so far. This article describes the behavior of QT dynamics assessed in a patient with ischemic heart disease after two documented cardiac arrests due to sustained ventricular arrhythmia. (PACE 2004; 27[Pt. I]:827–828)

CRT34: HEART RATE VARIABILITY BEHAVIOUR DURING CARDIAC RESYNCHRONIZATION THERAPY

The influence of cardiac resynchronization therapy (CRT) on heart rate variability (HRV) and therefore on autonomic nervous system in the heart has been discussed recently. Purpose of the study to assess the behaviour of HRV parameters in patients (pts) with chronic heart failure (CHF) treated with CRT therapy in three months follow-up. Methods The study group consisted of 17 pts (3F,14M, aged 53±9 years) with CHF at NYHA class III, EF<35% and significant systolic dyssynchrony of the left ventricle in whom BIV pacemakers InSyncIII (Medtronic) were implanted. HRV “time domain” parameters were calculated based on 24-hour digital Holter monitoring which was performed: before the procedure (I), 3-4(II) days after, 1(III), and 3(IV) months after BIV implantation. View this table: Conclusions The decrease of HRV immediately after BIV implantation and the tendency of HRV improvement during CRT therapy in three months follow-up are observed. CRT therapy may improve the autonomic tone in the heart.

CRT14: SLEEP APNEA IN PATIENTS TREATED WITH CARDIAC RESYNCHRONIZATION THERAPY

Purpose of the study to assess the SDB in pts with advanced chronic heart failure (CHF) treated with CRT in 3 months follow-up. Methods: The study group consisted of 17 pts (3F, 14M, aged 53±9 years) with CHF at NYHA class III, EF 5 and≤15) or Apneic (Est.AHI >15). The Est.AHI as well as the percentage of pts qualified for Normal, Borderline or Apneic class from baseline recordings and after 3 months follow-up were calculated. Results Mean value of the Est.AHI before BIV implantation was 7,5±4,6 (range: 23,3-0) and decreased significantly in 3 months follow-up having then the value of 4,6±5,5 (range: 13,0-0); p=0,003. After 3 months follow-up the total and significant reduction of Apneic class and the tendency to increase of Borderline class were observed. View this table: Conclusions In pts treated with CRT therapy in three months follow-up the improvement of sleep apnea parameters is observed. CRT therapy may have beneficial influence on sleep disordered breathing.