Estimation of spectral parameters of residual ECG signal during atrial fibrillation using autoregressive models

The application of AutoRegressive (AR) models to extract spectral parameters from residual ECG (rECG) signals is exploited. In particular, a new method based on AR spectra is employed to estimate the dominant atrial cycle length (DACL) on ECG obtained from patients undergoing episodes of atrial fibrillation (AF). The traditional FFT-based spectral approach will be compared with the new method. Potentialities and possible superior performances of AR spectra are documented and discussed

Influence of blood glucose on heart rate and cardiac autonomic function. The DESIR study.

International audienceOBJECTIVES:   To evaluate in a general population, the relationships between dysglycaemia, insulin resistance and metabolic variables, and heart rate, heart rate recovery and heart rate variability. METHODS:   Four hundred and forty-seven participants in the Data from an Epidemiological Study on the Insulin Resistance syndrome (DESIR) study were classified according to glycaemic status over the preceding 9 years. All were free of self-reported cardiac antecedents and were not taking drugs which alter heart rate. During five consecutive periods: rest, deep breathing, recovery, rest and lying to standing, heart rate and heart rate varability were evaluated and compared by ANCOVA and trend tests across glycaemic classes. Spearman correlation coefficients quantified the relations between cardio-metabolic risk factors, heart rate and heart rate varability. RESULTS:   Heart rate differed between glycaemic groups, except during deep breathing. Between rest and deep-breathing periods, patients with diabetes had a lower increase in heart rate than others (P(trend) < 0.01); between deep breathing and recovery, the heart rate of patients with diabetes continued to increase, for others, heart rate decreased (P(trend) < 0.009). Heart rate was correlated with capillary glucose and triglycerides during the five test periods. Heart rate variability differed according to glycaemic status, especially during the recovery period. After age, sex and BMI adjustment, heart rate variability was correlated with triglycerides at two test periods. Change in heart rate between recovery and deep breathing was negatively correlated with heart rate variability at rest, (r=-0.113, P < 0.05): lower resting heart rate variability was associated with heart rate acceleration. CONCLUSIONS:   Heart rate, but not heart rate variability, was associated with glycaemic status and capillary glucose. After deep breathing, heart rate recovery was altered in patients with known diabetes and was associated with reduced heart rate variability. Being overweight was a major correlate of heart rate variability

Estimation of spectral parameters of residual ECG signal during atrial fibrillation using autoregressive models

The application of AutoRegressive (AR) models to extract spectral parameters from residual ECG (rECG) signals is exploited. In particular, a new method based on AR spectra is employed to estimate the dominant atrial cycle length (DACL) on ECG obtained from patients undergoing episodes of atrial fibrillation (AF). The traditional FFT-based spectral approach will be compared with the new method. Potentialities and possible superior performances of AR spectra are documented and discussed

Different circadian behavior of the apex and the end of the T wave

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Cardiac effects of chronic oral beta-blockade: Lack of agreement between heart rate and QT interval changes.

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Ventricular repolarisation and holter monitoring: role of sympathetic blockade on the physiology of the QT/RR ratio

Circadian variations of the QT interval and its heart rate dependency have been established. However, the respective roles of the sympathetic and parasympathetic nervous systems in their regulation are still undetermined. Eighteen healthy volunteers (average age 39 +/- 7 years, 10 men) were recruited and selected randomly to receive either placebo or atenolol (100 mg/day). The treatments were crossed after 7 days. The rate dependency of the QT was assessed by day and by night by 24 hour Holter ECG monitoring. The effects of atenolol on the rate dependency of the QT interval depend on the time of day. During the daytime, the QT rate dependency was reduced by atenolol (0.180 (0.162: 0.198) versus 0.216 (0.195: 0.236) with placebo, p< 0.01) whereas during the night, the QT rate dependency was the same in both groups. Therefore, the betablocker is associated with an inversion of the daily modulation of the QT fate dependency. The daytime rate-dependency of the QT interval in decreased with betablocker therapy. This result suggests a direct or indirect influence of the sympathetic nervous system on the rate dependency of ventricular repolarisation

[Congenital long QT syndrome].

International audienceCircadian variations of the QT interval and its heart rate dependency have been established. However, the respective roles of the sympathetic and parasympathetic nervous systems in their regulation are still undetermined. Eighteen healthy volunteers (average age 39 +/- 7 years, 10 men) were recruited and selected randomly to receive either placebo or atenolol (100 mg/day). The treatments were crossed after 7 days. The rate dependency of the QT was assessed by day and by night by 24 hour Holter ECG monitoring. The effects of atenolol on the rate dependency of the QT interval depend on the time of day. During the daytime, the QT rate dependency was reduced by atenolol (0.180 (0.162:0.198) versus 0.216 (0.195:0.236) with placebo, p < 0.01) whereas during the night, the QT rate dependency was the same in both groups. Therefore, the betablocker is associated with an inversion of the daily modulation of the QT rate dependency. The daytime rate-dependency of the QT interval in decreased with betablocker therapy. This result suggests a direct or indirect influence of the sympathetic nervous system on the rate dependency of ventricular repolarisation

[Dynamics of ventricular repolarisation].

International audienceThe clinical value of assessing the QT interval is obvious as it is a marker of ventricular depolarisation and repolarisation and it allows identification of clinical situations carrying a high risk of ventricular fibrillation and sudden death. Until the last few years, analysis of ventricular repolarisation was based on analysis of conventional surface electrocardiography. Technical difficulties explain the limits of our knowledge of the dynamics of ventricular repolarisation. This situation is beginning to change rapidly by computerised analysis of Holter monitoring, opening up a particularly complex and important field of research. The duration of the QT interval depends on different factors, especially changes in electrolyte balance, effects of certain drugs, and changes in heart rate and autonomic nervous system tone. The difficulty resides in selecting the pertinent data in order to study separately the effects of heart rate and those of the autonomic nervous system. The initial results show that this analysis provides important information for diagnosis and probably prognosis, on the status of the myocardium and the action of the autonomous nervous system. They require confirmation and validation on larger series of patients with different pathological conditions

[Dynamics of ventricular repolarisation].

International audienceThe clinical value of assessing the QT interval is obvious as it is a marker of ventricular depolarisation and repolarisation and it allows identification of clinical situations carrying a high risk of ventricular fibrillation and sudden death. Until the last few years, analysis of ventricular repolarisation was based on analysis of conventional surface electrocardiography. Technical difficulties explain the limits of our knowledge of the dynamics of ventricular repolarisation. This situation is beginning to change rapidly by computerised analysis of Holter monitoring, opening up a particularly complex and important field of research. The duration of the QT interval depends on different factors, especially changes in electrolyte balance, effects of certain drugs, and changes in heart rate and autonomic nervous system tone. The difficulty resides in selecting the pertinent data in order to study separately the effects of heart rate and those of the autonomic nervous system. The initial results show that this analysis provides important information for diagnosis and probably prognosis, on the status of the myocardium and the action of the autonomous nervous system. They require confirmation and validation on larger series of patients with different pathological conditions