10 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
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
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
L’ouverture de l’orifice interne du col prédit mieux l’issue de la maturation cervicale que le score de Bishop chez les nullipares à 41 semaines d’aménorrhée
No full text
274 Assessment of the effect of antihypertension treatment on heart rate variability in hypertensive patients
No full text
Lean knowledge life cycle framework to support lean product development
No full textThis research thesis presents the development of a novel Lean Knowledge Life Cycle (LeanKLC) framework to support the transformation into a Lean Product Development (LeanPD) knowledge environment. The LeanKLC framework introduces a baseline model to understand the three dimensions of knowledge management in product development as well as its contextualisation with acclaimed LeanPD process models. The LeanKLC framework comprises 23 tasks, each accomplished in one of the seven key stages, these being: knowledge identification, previous knowledge capture, knowledge representation, knowledge sharing, knowledge integration, knowledge use and provision and dynamic knowledge capture.
The rigorous research methodology employed to develop the LeanKLC framework entailed extensive data collection starting with a literature review to highlight the gap in the current body of knowledge. Additionally, industrial field research provides empirical evidence on the current industrial perspectives and challenges in managing product development knowledge. This research was part of a European FP7 project entitled Lean Product and Process Development (LeanPPD), which provided the opportunity to involve industrial collaborators in action research to support practical aspects during the LeanKLC framework development.
The synthesis with the current LeanPD paradigm is accomplished by demonstrating the LeanKLC stages in two distinct streams related to the development of A3 thinking for problem solving and the development of trade-off curves to facilitate set based design at the conceptual stage. The novel LeanKLC is validated in two case studies providing the industry with detailed insights on real product development applications. In particular this research highlights that the LeanPD knowledge environment is a wide subject area that has not yet been thoroughly understood and that industry engagement in empirical research is vital in order to realise any form of LeanPD transformation
