Manel Ben Halima

247: Study of heart rate variability in high level athletes depending on the type of sport

Introduction There is a growing body of evidence suggesting that changes that affect the cardiovascular system during the practice of a high performance sport depends on the predominance of dynamic or static components that characterize each sport. Modifications of the autonomic nervous system (ANS) may explain these changes. There are non invasive tools that can study the ANS such as heart rate variability (HRV) assessed by Holter recording. Aim The purpose of this study is to compare the ANS in a group of elite athletes depending on the class of sports as classified by the 36th Bethesda Conference (dynamic versus static sports). Methods This study included sixty eight asymptomatic athletes who received a 24 Holter recording during their sports career. We analyzed HRV parameters exploring the sympathic nervous system (SDANN 24, SDNN, SDNN5) and the parasympathic nervous system (RMSSD and PNN50 Sports activities have been classified into two groups according to the predominance of the static component or dynamic and with reference to the classification of the 36th Bethesda Conference. Results Our population was composed of 68 athletes. Twenty one athletes practiced static sports and 47 dynamic sports. Both groups were comparable regarding age and sex. Static sport 21 Dynamic sport 47 p SDNN 24 (ms) 176.5±36.5 142±60 NS SDANN (ms) 148±32 99±41 NS SDNN5 (ms) 83±23.5 69.5±15.5 NS RMSSD (ms) 52.5±24 47±15 NS PNN50 24.5±16.5 23.5±10.5 NS Conclusion There was no significant difference in sympathetic and parasympathetic tone among elite athletes in a sport dominated by static component compared to those practicing the sports dominated by the dynamic component.

201: Are QT intervals correlated to apnea-hypopnea index in obstructive sleep apnea?

Introduction Several studies proved that obstructive sleep apnea (OSA) is associated with cardio-vascular diseases such as cardiac arrhythmia. QT duration and dispersion reflect the heterogeinity of ventricular repolarization and are considered as precursors of ventricular arrhythmia Aim The aim of this study is to assess the relation between the severity of OSA parameters as apnea hypopnea index and QT intervals. Methods Forty patients (18 men and 22 women) who were diagnosed with OSA by overnight polysomnography were included in this prospective study. The mean age was 56±10 years old. They were all in sinus rhythm. Before initiating continuous positive airway pressure therapy, we calculated on a 12 lead ECG : QT duration (QTend) corrected to Bazett formula and QT dispersion (QT end max -QT end min). Results Twenty four patients had severe OSA (AHI >30), 4 had moderate OSA (AHI between 15 and 30) and 12 had a mild OSA (AHI between 5 and 15). There was a significant positive correlation between QT dispersion and AHI (r=0.48, p=0.001) Conclusion The severity of OSA seems to be correlated with ventricular repolarization heterogeinity These results suggest that the higher is the AHI the higher is the risk of ventricular arrhythmia occurence. Further studies are needed to validate these results.

203: Correlation between P wave variables and apnea-hypopnea index in obstructive sleep apnea

Introduction Obstructive sleep apnea (OSA) is associated with several cardio-vascular abnormalities as atrial fibrillation (AF). AF occurrence in OSA increases the risk of stroke which worsens the prognosis of these patients. P wave dispersion (Pd) and maximal P wave duration (P max) are simple electrocardiographic parameters which reflect atrial conduction abnormalities and have been reported to be predictors of atrial fibrillation Aim the aim of this study is to determine the correlation between apnea-hypopnea index (AHI) and P wave dispersion and maximal P wave duration. Methods Forty patients (18 men and 22 women) who were diagnosed with OSA by overnight polysomnography were included in this prospective study. The mean age was 56±10 years old. They were all in sinus rhythm. Before initiating continuous positive airway pressure therapy, we evaluated on a 12 lead ECG P wave duration and P wave dispersion (P max - P min). Results Twenty four patients had severe OSA (AHI >30), 4 had moderate OSA (AHI between 15 and 30) and 12 had a mild OSA (AHI between 5 and 15). Mean P max duration was 119±21 ms. P wave dispersion was 93±6 ms. There was a significant positive correlation between P max and AHI (r= 0.45, p=0.001) and between P wave dispersion and AHI (r=0.42, p=0.001) Conclusion The severity of OSA seems to be correlated with the importance of atrial conduction abnormalities. These results suggest the higher is the AHI the higher is the risk of AF occurrence in OSA. Further studies are needed to validate these results.

223 Seasonal variation of heart rate variability in hypertensive patients

Introduction Epidemiologic data suggest that season changes could explain the occurrence of cardiovascular complications particularly during winter. Autonomic nervous system has been implicated in the increase of this risk. Heart rate varibility (HRV) is a non invasive tool exploring sympathic and parasympathic systems. Aim The study of parameters of HRV during season changes in hypertensive patients and to compare them to healthy subjects. Methods 85 hypertensive patients underwent 24 holter recording during one year; from March 2006 to March 2007. The patients underwent recordings during the four seasons: spring, summer, autumn and winter. We studied changes in HRV in the temporal domain and the spectral domain during seasonal changes. Seasonal variation of HRV were also studied in 40 healthy controls and compared to those of hypertensive patients. Results W e noticed a decrease in the sympathic tone in hypertensive patients during warm and hot seasons (spring and summer) and a relative increase in the sympathic tone during cold seasons. There was also a trend toward an increase in the sympathic tone during cold seasons in healthy subjects. There were no significant changes concerning HRV parameters exploring the parasympathic during the whole year in hypertensive patients and healthy controls. Conclusion There is a seasonal variation in autonomic nervous system modulation. These variations are more accentuated in hypertensive patients with an increase in the sympathic tone during cold seasons. These variations could be deleterious on cardiovascular system and could explain the increases in cardiovascular events during winter in hypertensive patients.