View clinical trials related to Heart Rate Variability.
Filter by:Baroreflex sensitivity is integral to blood pressure regulation, and varies among healthy, normotensive individuals. A reduced compensatory ability of baroreflex buffering in patients with carotid denervation results in blood pressure variability and an elevated blood pressure response to mental stress. Furthermore, 24-hour ambulatory blood pressure variability may also be a significant and independent risk determinant of cardiovascular disease. It remains unknown whether the degree of baroreflex sensitivity and ambulatory blood pressure variability are predictive of the pressor response to sympathoexcitatory stress in healthy humans. In this study the investigators propose a comprehensive evaluation of the relationships among the pressor and forearm vasodilator response to sympathoexcitation, ambulatory blood pressure variability, and baroreflex sensitivity in healthy normotensive subjects. Ultimately this study will provide preliminary data and protocol development for large-scale high resolution phenotyping in population-based trials aimed at determining the functional relevance of candidate gene variation in intermediate physiological traits pertinent to the pathogenesis of hypertension and cardiovascular disease.
Air pollution is a major cause of cardiorespiratory morbidity and mortality. The exact components of air pollution that underlie the cardiovascular effects are not yet known, but combustion-derived particulate matter is suspected to be the major cause. Epidemiological studies have shown that exposure to air pollution causes exacerbation of existing cardiorespiratory conditions leading to increased hospital admissions and death. The investigators have recently conducted a series of controlled exposure studies to urban particulate matter and diesel exhaust in healthy volunteers and patients with coronary heart disease. The investigators found that controlled exposure to dilute diesel exhaust in patients with prior myocardial infarction induced asymptomatic myocardial ischaemia with an increase in electrocardiographic measures of myocardial ischaemia. Whilst important, further questions remain: (i) does air pollution exposure exacerbate ischaemia and reduce exercise tolerance in patients with symptomatic angina pectoris, (ii) do "real world" exposures as encountered in the urban environment of major cities have similar effects, and (iii) can a simple face mask intervention to reduce exposure to particulate air pollution improve health outcomes in patients with coronary heart disease?
Exposure to air pollution is an important risk factor for cardiovascular morbidity and mortality, and is associated with increased blood pressure, reduced heart rate variability, endothelial dysfunction and myocardial ischaemia. The study objectives were to assess the potential cardiovascular benefits of reducing personal particulate air pollution exposure by wearing a facemask in healthy volunteers.
Chronic beta-adrenoceptor blockade is known to improve outcome of high risk patients whereas amelioration of autonomic activity was demonstrated to be a major cause of outcome improvement. Therefore, perioperative beta-adrenoceptor blockade is recommended in patients with Revised Cardiac Risk Index score of three or greater. The investigators hypothesise that preoperative intravenous beta-adrenoceptor blockade for treatment of hypertension and/or tachycardia improves autonomic activity reflected by increase of Total Power of Heart Rate Variability. Material and Methods: After IRB approval 20 patients scheduled for elective cardiac surgery were included into the study. Routine medication was continued throughout the study as recommended by the guidelines. HRV (TP and Low to High Frequency ratio (LF/HF) reflecting sympathetic to parasympathetic balance) was analysed prior to induction of general anesthesia and beta-adrenoceptor blockade in all patients (Baseline). Patients were assigned by their baseline hemodynamics. Patients with hypertension (systolic blood pressure > 140mmHg or diastolic blood pressure > 90mmHg) or tachycardia (heart rate > 80bpm) were assigned to group BETA-BLOCK. In this group metoprolol-boli (2mg) were administered intravenously in stepwise manner until hemodynamic values decreased to normal. Total dosage was recorded. After normalisation of hemodynamics, second HRV analysis was performed (Intervention). Normotensive and normocardic patients were assigned to group CONTROL. No intervention was performed. Statistics: Mann Whitney U test for comparison between groups and between events Baseline and Intervention within group BETA-BLOCK, p<0.05.