35 research outputs found
223 Seasonal variation of heart rate variability in hypertensive patients
No full textIntroductionEpidemiologic 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.AimThe study of parameters of HRV during season changes in hypertensive patients and to compare them to healthy subjects.Methods85 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.ResultsWe 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.ConclusionThere 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
173 Study of the circadien variation of the QT dynamics in myocardial infarction
No full textIntroductionThe relation between the QT interval and heart rate is linear. The QT interval/RR interval relationship is generally described as QT dynamics. the linear QT/RR slope is influenced by the autonomic nervous system. In healthy individuals, the slope exhibits circadian variations: it is steeper during the day than during the night.AimThe aim of this study is to evaluate the circadian variation of the QT interval and the QT/RR slope in patients experiencing myocardial infarction.MethodsThis prospective study included 90 patients having myocardial infarction. They underwent 21 days after the acute phase, 24 hours ambulatory ECG (Holter) recording. The following parameters were studied : the QT end interval (QTe), the QT apex interval (QTa) and the slopes of QTe/RR and QTa/RR during diurnal and nocturnal periods.ResultsThere was no significant difference regarding the QTe and the QTa intervals during the day and night. The mean diurnal slope and nocturnal slopes of QTe/RR were similar (0,147±0,073 vs 0,131±0,062, p=NS). The mean diurnal slope and nocturnal slopes of QTa/RR were also comparable (0,123±0,067 vs 0,119±0,065, p=NS).ConclusionThe lack of circadian variation of the QT interval and the linear QT/RR slope in myocardial infarction patients reflects an imbalance in the autonomic nervous system. These results suggest an increase in the nocturnal sympathic tone and may be associated with a higher risk of arrhythmia in this population. Further studies are needed to evaluate the role of the QT/RR slope in risk stratification after myocardial infarction
236 The effects of dipper and non dipper status on heart rate variability and heart rate turbulence in essential hypertension
No full textIntroductionThe relation between the autonomic nervous system and the circadian pattern of blood pressure in hypertensive patients is not well established.AimThe aim of this prospective study is to compare parameters of heart rate variability (HRV) and heart rate turbulence (HRT), non invasive measures reflecting the sympathetic and parasympathetic modulations of heart rate, in dipper and non dipper hypertensive patients.Methods47 hypertensive patients (24 males and 23 females, age = 57±10 years old) underwent 24 hour Holter recording and 24 hour ambulatory blood pressure monitoring (ABPM). Patients whose nocturnal average blood pressure (BP) levels decreased by more than 10% compared to their day time BP levels were considered as dippers, and those whose levels did not decrease as non dippers. Diabetes and ischemic heart disease were exclusion criteria.Results30 patients were dippers and 17 patients were non dippers. Dipper and non dipper patients were comparable regarding age, sex and mean blood pressure. There was no significant difference in average HRV and HRT parameters between both groups (table 1).Table. Comparison of HRV and HRT parametersDippers N = 30Non dippers N = 17PSDNN 5 min (ms)53±547±3NSSDANN 5 min (ms)106±3597±24NSRMSSD (ms)38±3131±13NSLF (ms2)620±146411±134NSHF (ms2)387±133194±32NSTO (%)-0.0244-0.0152NSTS (ms/RIR)7.72±1.977.43±1.36NSIn dipper patients the LF/HF was higher during daytime compared to the night (3.3±0.5 vs 2.05±0.27, p=0.0041) where as no significant difference was noticed in non dipper patients (3.3±0.24 vs 2.7±0.33, p = NS).Conclusionthese results suggest that despite similar global HRV and HRT parameters in dippers and non dippers, non dipper patients have an imbalance of the circadian sympathic-vagal tonus pattern with a high nocturnal sympathic tonus. These data may partially explain the higher incidence of cardiovascular events reported in non dipper patients
243 Assessment of heart rate turbulence in hypertensive patients
No full textIntroductionHeart rate turbulence (HRT) has been currently believed to represent a non invasive method of measurement of the baroreflex-sensitivity. Studies suggested that it may reflect vagal robustness in antagonizing the effects of sympathic activity.Most studies exploring HRT have been dealt in ischemic and heart failure patients. To date, only few studies investigated these parameters in patients with hypertension.Aimthe aim of this study is to compare HRT parameters, derived from Holter recordings, in hypertensive patients and healthy controls.MethodsIn this prospective studies, 85 patients with essential hypertension (45 females and 40 males, age 60±12 years old) and 40 healthy controls matched to age and gender underwent Holter recordings with analysis of HRT parameters: turbulence onset (TO) and turbulence slope (TS). Heart rate variability parameters reflecting sympathic (SDNN, SDANN, LF) and parasympathic activity (RMSSD, HF) were also studied. Patients with diabetes, ischemic heart disease and atrial fibrillation were excluded.Resultsthere was no significant difference regarding HRT parameters as well as RMSSD and HF between hypertensive patients and healthy controls. SDNN, SDANN and LF were significantly lower in hypertensive patients (table 1). This difference persisted after multivariate analysis.Table. Comparison between HRT and HRV parameters in hypertensive patients and healthy controlsHypertensive patients (n=85)Healthy controls (n=40)pTO-0.0196-0.0120NSTS8,669,68NSSDNN117±33141±450.001SDANN101±29125±42<0.0001RMSSD37±2244±20NSLF564±53830±600.02HF301±34436±40NSConclusionHRT parameters are similar in essential hypertensive patients and healthy controls. Other Holter derived parameters exploring the parasympathic tone were also comparable suggesting that the vagal tone is preserved in essential hypertension. This latter is associated with a significant higher sympathetic activity. Further studies are needed to determine the pathophysiologic significance and the prognostic value of this loss of modulation of the autonomic nervous system and whether it could have therapeutic implications
212 Study of the effect of mode of pacing on ventricular repolarization in heart failure patients
No full textBackgroundCardiac resynchronization therapy (CRT) is a well established treatment in selected patients with heart failure. The non physiological ventricular activation sequence has been implicated in the occurrence of sudden death after CRT. There is conflicting date concerning the effect of different pacing modes on ventricular repolarization in heart failure patients.PurposeAssessing the effects of biventicular (Bi V), left ventricular (LV) epicardial pacing and right ventricular endocardial pacing (RV) on QT intervals (QT end, QT apex, JT) and transmural dispersion of repolarization (TDR) in patients with heart failure having CRT.Methods20 patients (15 men and 5 women, age = 63.4±11 years) with NYHA III-IV heart failure due to left ventricular systolic dysfunction and cardiac dyssynchrony received CRT. We measured QT end intervals, JT intervals and TDR according to recommended methods on a 12 lead ECG recorded at baseline and after implant. After implant, ECG was recorded with temporary right ventricular pacing, temporary left ventricular pacing and then the final pacing mode : simultaneous biventricular pacing.ResultsThere was no significant difference between QT end interval, JT interval and TDR at baseline and after implant with different pacing modes.ConclusionIn our study, we noticed no effect of pacing modes on repolarization in patients with heart failure. The high incidence of sudden death observed in CRT may be explained by competitvity of modes of death rather than induced abnormal repolarization
175 Is high sensitive C reactive protein related to clinical and echocardiographic risk of thrombo-embolism in patients with atrial fibrillation?
No full text247: Study of heart rate variability in high level athletes depending on the type of sport
No full textIntroductionThere 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.AimThe 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).MethodsThis 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 PNN50Sports 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.ResultsOur 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 21Dynamic sport 47pSDNN 24 (ms)176.5±36.5142±60NSSDANN (ms)148±3299±41NSSDNN5 (ms)83±23.569.5±15.5NSRMSSD (ms)52.5±2447±15NSPNN5024.5±16.523.5±10.5NSConclusionThere 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
