25 Clinical Trials for Various Conditions
Chronic kidney disease (CKD) is associated with a higher risk of cardiovascular disease and death. An overactive sympathetic nervous system in CKD patients is one of the major mechanisms increasing the cardiovascular risks in this patient population. A potential signal driving sympathetic nerve activity (SNA) involves accumulation of the endogenous nitric oxide synthase (NOS) inhibitor asymmetric dimethylarginine (ADMA). ADMA is elevated in CKD and is a strong, independent predictor of future cardiovascular events in these patients. . The goal of this study is to determine whether overcoming the accumulation of endogenous ADMA with acute L-arginine infusion reduces SNA in CKD patients.
This study aims to evaluate the effect of Suvorexant on sympathetic nerve activity and baroreflex function in subject with chronic insomnia. The investigator's central hypothesis is that Suvorexant will reduce sympathetic nerve activity and improve baroreflex function when compared to placebo.
The goal of this study is to evaluate the acute effects of a long-acting bronchodilator on pulmonary function, vascular function and muscle sympathetic nerve activity in individuals with COPD. Individuals will be recruited from previous pulmonary research cohorts at The University of Iowa hospitals and clinics. Individuals that are interested in the study and are deemed eligible to participate will have a total of 3 visits to the laboratory, which includes the screening and consent (visit 1) that will last approximately 1 hour. Visits 2 and 3 are experimental visits and will be more extensive (\~4 hours). Participants will be randomized to receive either a long-acting bronchodilator or a placebo inhaler at the first experimental visit, followed by either the placebo inhaler or the long-acting bronchodilator at the second experimental visit. Assessments of pulmonary function, vascular function (via non-invasive, well-established techniques), and muscle sympathetic nerve activity will be performed at both experimental visits.
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.
Stress (Takotsubo) cardiomyopathy (SC) is a peculiar form of acute, reversible myocardial dysfunction predominantly affecting the apical and mid left ventricular segments. In this institution over the last two to three years the investigators have identified more than a dozen patients with stress cardiomyopathy. The investigators' overarching goal is to characterize these individuals with the hope of identifying risk factors and developing strategies to prevent the occurrence of SC in situations where the likelihood in susceptible individuals may be high.
The purpose of this study is to determine if either hypoglycemia or exercise cause differential responses in muscle and skin sympathetic nerve activity.
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.
The goal of this clinical trial is to investigate the autonomic and vascular function in men and women with Type 1 diabetes. The main questions it aims to answer are: 1. Patients with type 1 diabetes exhibit attenuated vascular function during steady-state exercise 2. Patients with type 1 diabetes have altered autonomic function at rest and during exercise pressor reflex 3. Patients with type 1 diabetes have attenuated muscle sympathetic activity
In light of the ongoing COVID-19 pandemic, wearing a mask has become a universal standard as an attempt to reduce the spread of COVID-19. As of 2020, more than half of all U.S. states have implemented a state wide mandated mask policy. There are many schools of thought regarding the benefits and risks of donning a mask to prevent the spread of COVID-19. There is an unproven theory among some that wearing a mask interferes with our natural respiratory function, causing hypoxia, altered mental status and other various health issues. This dangerous perception has led some to believe wearing a mask is harmful, and encourages against wearing a mask in public. This theory, recently refuted by a study investigating oxygen levels while participants wore masks, performed in 2020 encouraged increased compliance with wearing masks. Another study, preformed by evaluated whether gas exchange abnormalities occurred with the use of surgical masks in subjects with and without lung function impairment. The conclusions of the study showed that regardless of lung function impairment, the presence of surgical masks did not impact gas exchange. Additionally, a more recent study concluded that the presence of a facemask did not have a significant change in physiologic parameters while during exercise. Although there is evidentiary support that facemasks do not negatively affect oxygen status and physiologic capacity, there is not strong evidence examining the relationship between ETCO2 and facemasks. The relationship between ETCO2 and facemasks is one of importance because mild decreases in oxygen have much less dangerous effects compared to the effects of rapid accumulations of carbon dioxide. Increases in end tidal carbon dioxide lead to confusion, acidosis and in severe cases, respiratory distress and failure. A study performed in 1989 showed that hypercapnia has greater increases in blood pressure, minute ventilation and sympathetic nerve activity than hypoxia. In this newly proposed study, healthy volunteers will all wear the same type of three layer surgical mask. Their end tidal carbon dioxide will be measured while at rest without a mask, while resting with a mask and then after walking 100 meters in the mask. While previous studies have focused on changes in oxygen, there is a lack of research dedicated to analyzing end tidal carbon dioxide. This study will hope to show evidence supporting that there is no increase in end tidal carbon dioxide while wearing a mask.
This study has two phases: Phase 1 is to examine blood pressure, microvascular function, and sympathetic nerve activity in mid-life adult binge drinkers vs. alcohol abstainers/moderate drinkers. Phase 2 is to examine the effect of 8-week aerobic exercise training on blood pressure, microvascular function, and sympathetic nerve activity in mid-life adult binge drinkers
E-cigarettes are marketed as an alternative to smoking for those who want to decrease the health risks of tobacco. Tobacco cigarettes increase heart rate (HR) and arterial pressure, while reducing muscle sympathetic nerve activity (MSNA) through sympathetic baroreflex inhibition. The acute effects of e-cigarettes on arterial pressure and MSNA have not been reported: our purpose was to clarify this issue. Using a randomized crossover design, participants inhaled on a JUUL containing nicotine (59 mg/ml) and a similar placebo e-cigarette (0 mg/ml).
Brain blood flow regulation and autonomic dysfunction will be measured in Veterans with and without Gulf War Illness who served in the Gulf War between 1990 and 1992.
Brain blood flow, blood pressure, and neurovascular control mechanisms will be measured in middle-aged adults before and after a brief intervention period. The intervention will consist of changing the time in which the participant consumes food each day.
Rosacea is a common skin disorder which causes facial redness and inflammation in about 16 million Americans, from an unknown cause. Many triggers of rosacea symptoms are stressors that affect the sympathetic ("fight or flight") portion of the nervous system, and a recent pilot study suggests there is sympathetic dysfunction in rosacea. This project will benefit patients, clinicians, and basic scientists by increasing our understanding of sympathetic nervous system involvement in rosacea symptoms in order to develop improved treatments for patients with rosacea.
Traditional medical treatments are often based on research done exclusively in males, and recent research efforts in the physiology community have highlighted critical sex differences in disease presentation and progression. For example, the relative risk of fatal heart disease is 50% greater in obese, diabetic women as compared to their male counterparts, and women appear to respond differently to lifestyle interventions such as exercise compared with men. Chronic passive heat exposure (hot tub use) provides alternative or supplemental therapeutic potential for improving cardiovascular and metabolic health in obese women. In addition, passive heat exposure may offer specific cellular protection from stresses like a lack of blood flow (ischemia), which is the primary cause of fatal coronary heart disease. This study is investigating the possible cardiovascular and metabolic health benefits of chronic passive heat exposure, and whether regular hot tub use (3-4 days per week for 8-10 weeks) may reduce obese womens' cardiometabolic risk. The investigators are examining cardiovascular health through blood pressure, blood vessel stiffness, sympathetic ('fight or flight') activity, and responsiveness to stresses like increased or decreased blood flow. The investigators are also examining metabolic health through an oral glucose tolerance test and a subcutaneous fat biopsy. The goal of this research is to develop a therapy targeted toward the specific health needs and complications of obese women, in an effort to improve cardiovascular and metabolic health and provide therapeutic alternatives in this high-risk population.
The overall goal of this proposed study is to evaluate the underlying mechanisms of neural control of blood flow in the lower extremities in humans with restless leg syndrome (RLS). At least 15% of the general public suffers from RLS and many more may go undiagnosed. This unfortunate disorder leads primarily to a disturbing sensation within the patient's lower extremities that requires movement for relief (1, 2). The central hypothesis of our study is that physiological changes in lower limb blood flow as a result of thoracolumbar epidural Spinal Cord Stimulation (SCS) lead to the relief of RLS.
Heart failure with preserved ejection fraction (HFpEF) is the fastest growing form of heart failure with a high morbidity and mortality rate, and is associated with severe exercise intolerance. The mechanisms responsible for the reduced exercise tolerance remain poorly understood. The investigators propose a novel paradigm shift, focusing on peripheral limitations to exercise. In particular, the investigators will test the hypothesis that muscle sympathetic nerve activity (MSNA) is elevated in older HFpEF patients compared to healthy controls, and is associated with reduced exercise tolerance. The investigators will also test whether 16-weeks of exercise training will lower MSNA compared to attention control, and correlate with improved exercise tolerance in older HFpEF patients.
Randomized controlled trial of electronic cigarettes with nicotine, without nicotine, nicotine inhaler, and sham-control on endothelial function, oxidative stress and sympathetic nerve activity
Patients with high aldosterone hormone have higher blood glucose than normal people. This study is being done to understand how aldosterone hormone affects the nerve activity that controls blood flow in the muscles and blood glucose. The information may be helpful in selecting blood pressure medications which can improve not only blood pressure but also improve blood sugar.
The goals of this proposal are to determine the effects of hypoglycemia on the autonomic nervous system.
The purpose of this study is to determine if Nebivolol a) attenuates the angiotensin II (Ang II)-induced increase in oxidative stress, thereby attenuating Ang II-induced vasoconstriction; and b) attenuates sympathetic mediated vasoconstriction during exercise, thereby reducing functional skeletal muscle ischemia in hypertensive patients.
People with heart failure often have weakness in their leg muscles. This study will determine whether the leg weakness is due to very high adrenaline levels and whether the medication clonidine can improve leg weakness.
The purpose of this study is to improve the scientific understanding of the cardiovascular actions of cocaine, in particular the ability of cocaine to increase blood pressure.