View clinical trials related to Sympathetic Nerve Activity.
Filter by:The purpose of this study is to examine the hypothesize that 4 weeks of sympathetic nerve activity (SNA) inhibition (oral clonidine) will cause a significant reduction in circulating blood concentrations and endothelial cell expression of inflammatory markers (e.g., TNF-α, IL-6). Our study is a prospective study using a randomized, double-blinded design to test 4 weeks of SNA blockade (oral clonidine) compared with a BP-lowering control condition (diuretic, hydrochlorothiazide) or a placebo.
The investigators seek to understand how reflexes from the breathing muscles influence blood pressure during exercise. Furthermore, the investigators are determining if increasing breathing muscle strength (via inspiratory muscle training) influences the respiratory muscle contribution to blood pressure during exercise.
Since the invention of electrocardiogram (ECG), ECG has been an important part of clinical practice. A primary reason for the popularity of the ECG is that it is non-invasive and can be performed in any patient by placing electrodes on the skin. The present methods of ECG recording focus on detecting electrical signals from the heart. the investigators propose that with high frequency sampling and high pass filtering, the investigators can also record SNA from the skin. The somata of the subcutaneous sympathetic nerves on the skin are located at the ipsilateral cervical and stellate ganglia. Because the left stellate ganglion nerve activity (SGNA) is known to trigger cardiac arrhythmias, including AF, VF and VF, It is possible that skin SNA can also be used for arrhythmia prediction. the investigators tested that hypothesis in our preclinical studies (supported by R01 HL71140) using canine models. The results showed that subcutaneous nerve activity (SCNA) recorded with implanted electrodes can be used to estimate stellate ganglion nerve activity(SGNA) in normal dogs and in a canine model of ventricular arrhythmia and sudden death. the investigators also showed that SCNA is more accurate than heart rate variability in estimating cardiac sympathetic tone in ambulatory dogs with myocardial infarction.Therefore, SKNA and SCNA may be useful in estimating cardiac sympathetic tone. In addition to studying the autonomic mechanisms of cardiac arrhythmia, these new methods may have broad application in studying both cardiac and non-cardiac diseases. For example, sympathetic tone is important in the pathogenesis of heart failure, atherosclerosis, peripheral neuropathies, epilepsy, vasovagal syncope, renal failure, hypertension and many others diseases. Direct SKNA and SCNA recording may provide new approaches to study the mechanisms of these common diseases. SKNA recording may also have immediate clinical applications by assisting in the diagnosis and treatment of hyperhidrosis (sweaty palms), paralysis, stroke, diabetes, and neuromuscular diseases. It may be used to assist biofeedback monitoring performed by neurologists to control neuropsychiatric disorders. Because of these potential clinical and commercial applications, the investigators propose that this research project is significant. b. Innovation - Using conventional electrodes on the skin to record SNA. The neuECG utilizes the conventional skin electrodes that are widely used in health care facilities. Skin SNA had been recorded using microneurography techniques, and had been estimated using cutaneous blood flow (vasodilator responses) skin temperature, skin conductance and sweat release. However, microneurography cannot be used in ambulatory patients. The other methods are not direct measurements of SNA. neuECG is the first method that can directly and non-invasively measure the SNA from the skin. - Automated real-time signal processing. the investigators will develop signal processing software to automatically eliminate noise, such as that generated by muscle contraction, electrical appliances, body motion, respiration, and radiofrequency signals. The remaining signals are then processed to separately display in real time to provide health care providers a new method to instantly estimate sympathetic tone. The ECG signals are used for automated arrhythmia detection while the SNA signals are available for risk stratification. This approach allows us to improve and broaden the clinical application of Einthoven's original invention by simultaneous detecting ECG and SNA from the skin. - SKNA patterns as new biomarkers. the investigators have identified unique SKNA patterns that precede the onset of human AF. If proven correct by Specific Aim 3, this new biomarker can help physicians to estimate the arrhythmia risk and to predict the efficacy of catheter ablation for AF.
Activation of the sympathetic nervous system is associated with increased risk of ventricular arrhythmias and sudden cardiac death (SCD). Development of simple, noninvasive, reliable tools to measure sympathetic outflow in human subjects is therefore highly desirable. Microneurography is the current gold standard measurement technique, whereby multiunit postganglionic sympathetic nerve activity is recorded with tungsten ultrafine microelectrodes inserted selectively into nerve fascicles of the peroneal nerve. Though this technique is considered extremely safe, and has been used successfully for decades in human translational physiology experiments, it has not been adopted for routine clinical assessment due to the requirement for sophisticated equipment and specific technical training and skills. Alternatively, many have adopted heart rate variability as a simple, noninvasive technique for assessing sympathetic nerve activity. However, heart rate variability does not directly measure sympathetic nerve activity, and there is much debate in the literature as to the exact source of sympathetic nerve traffic. For example, many believe it is an accurate reflection of cardiac sympathetic nerve activity, but does not accurately reflect changes in muscle or skin sympathetic nerve activity. To address these limitations, the investigators have developed a simple, noninvasive technique to measure sympathetic nerve activity using surface electrodes. Despite its great promise, this new approach has not yet been directly validated. The purpose of this study is therefore to validate this new technique (refered to as EKG-NA) against the current gold standard measurement technique, microneurography.
Recent evidences suggest that obstructive sleep apnea (OSA) can contribute to cardiovascular disease even in the absence of hypertension. However, there are few data regarding the impact of OSA on the sympathetic system in apparently normotensive patients with OSA as well as the impact of treatment with continuous positive airway pressure in different sites of activation (heart, peripheral nerves and circulating catecholamines)