A cortical potential reflecting cardiac function

Emotional trauma and psychological stress can precipitate cardiac arrhythmia and sudden death through arrhythmogenic effects of efferent sympathetic drive. Patients with preexisting heart disease are particularly at risk. Moreover, generation of proarrhythmic activity patterns within cerebral autonomic centers may be amplified by afferent feedback from a dysfunctional myocardium. An electrocortical potential reflecting afferent cardiac information has been described, reflecting individual differences in interoceptive sensitivity (awareness of one's own heartbeats). To inform our understanding of mechanisms underlying arrhythmogenesis, we extended this approach, identifying electrocortical potentials corresponding to the cortical expression of afferent information about the integrity of myocardial function during stress. We measured changes in cardiac response simultaneously with electroencephalography in patients with established ventricular dysfunction. Experimentally induced mental stress enhanced cardiovascular indices of sympathetic activity (systolic blood pressure, heart rate, ventricular ejection fraction, and skin conductance) across all patients. However, the functional response of the myocardium varied; some patients increased, whereas others decreased, cardiac output during stress. Across patients, heartbeat-evoked potential amplitude at left temporal and lateral frontal electrode locations correlated with stress-induced changes in cardiac output, consistent with an afferent cortical representation of myocardial function during stress. Moreover, the amplitude of the heartbeat-evoked potential in the left temporal region reflected the proarrhythmic status of the heart (inhomogeneity of left ventricular repolarization). These observations delineate a cortical representation of cardiac function predictive of proarrhythmic abnormalities in cardiac repolarization. Our findings highlight the dynamic interaction of heart and brain in stress-induced cardiovascular morbidity

Multicenter trial of the proficiency of smart quantitative sensation tests

Introduction : We assessed proficiency (accuracy and intra‐ and intertest reproducibility) of smart quantitative sensation tests (smart QSTs) in subjects without and with diabetic sensorimotor polyneuropathy (DSPN). Methods : Technologists from 3 medical centers using different but identical QSTs independently assessed 6 modalities of sensation of the foot (or leg) twice in patients without ( n  = 6) and with ( n  = 6) DSPN using smart computer assisted QSTs. Results : Low rates of test abnormalities were observed in health and high rates in DSPN. Very high intraclass correlations were obtained between continuous measures of QSTs and neuropathy signs, symptoms, or nerve conductions (NCs). No significant intra‐ or intertest differences were observed. Conclusions : These results provide proof of concept that smart QSTs provide accurate assessment of sensation loss without intra‐ or intertest differences useful for multicenter trials. Smart technology makes possible efficient testing of body surface area sensation loss in symmetric length‐dependent sensorimotor polyneuropathies. Muscle Nerve 49 : 645–653, 2014Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106991/1/mus23982.pd

Система дистанційної освіти та її захист

BACKGROUND: It is currently unknown whether early immunomodulatory treatment in relapsing-remitting MS (RRMS) can delay the transition to secondary progression (SP). OBJECTIVE: To compare the time interval from onset to SP in patients with RRMS between a contemporary cohort, treated with first generation disease modifying drugs (DMDs), and a historical control cohort. METHODS: We included a cohort of contemporary RRMS patients treated with DMDs, obtained from the Swedish National MS Registry (disease onset between 1995-2004, n = 730) and a historical population-based incidence cohort (onset 1950-64, n = 186). We retrospectively analyzed the difference in time to SP, termed the "period effect" within a 12-year survival analysis, using Kaplan-Meier and Cox regression analysis. RESULTS: We found that the "period" affected the entire severity spectrum. After adjusting for onset features, which were weaker in the contemporary material, as well as the therapy initiation time, the DMD-treated patients still exhibited a longer time to SP than the controls (hazard ratios: men, 0.32; women, 0.53). CONCLUSION: Our results showed there was a longer time to SP in the contemporary subjects given DMD. Our analyses suggested that this effect was not solely driven by the inclusion of benign cases, and it was at least partly due to the long-term immunomodulating therapy given

The effect of stimulation technique on sympathetic skin responses in healthy subjects

The aim of this study was to collect normative data for sympathetic skin responses (SSR) elicited by electrical stimulus of the ipsilateral and contralateral peripheral nerves, and by magnetic stimulus of cervical cord. SSRs were measured at the mid-palm of both hands following electrical stimulation of the left median nerve at the wrist and magnetic stimulation at the neck in 40 healthy adult volunteers (mean age 52.2 ± 12.2 years, 19 males). The onset latency, peak latency, amplitude and area were estimated in “P” type responses (i.e., waveforms with a larger positive, compared to negative, component). SSR onset and peak latency were prolonged when the electrical stimulus was applied at the contralateral side (i.e., the SSR recorded in the right palm P < 0.001). The onset latency was similar on both sides during cervical magnetic stimulation. However, peak latency was faster on the left side (P < 0.03). Comparison of electrical and magnetic stimulation revealed that both the onset and peak latency were shorter with magnetic stimulation (P < 0.001). The latency of a SSR varies depending on what type of stimulation is used and where the stimulus is applied. Electrically generated SSRs have a longer delay and the delay is prolonged at the contralateral side. These factors should be taken into account when interpreting SSR data

Methods of investigation for cardiac autonomic dysfunction in human research studies

This consensus document provides evidence‐based guidelines regarding the evaluation of diabetic cardiovascular autonomic neuropathy (CAN) for human research studies; the guidelines are the result of the work of the CAN Subcommittee of the Toronto Diabetic Neuropathy Expert Group. The subcommittee critically reviewed the limitations and strengths of the available diagnostic approaches for CAN and the need for developing new tests for autonomic function. It was concluded that the most sensitive and specific approaches currently available to evaluate CAN in clinical research are: (1) heart rate variability, (2) baroreflex sensitivity, (3) muscle sympathetic nerve activity, (4) plasma catecholamines, and (5) heart sympathetic imaging. It was also recommended that efforts should be undertaken to develop new non‐invasive and safe CAN tests to be used in clinical research, with higher sensitivity and specificity, for studying the pathophysiology of CAN and evaluating new therapeutic approaches. Copyright © 2011 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/86917/1/1224_ftp.pd

Periprandial changes of the sympathetic–parasympathetic balance related to perceived satiety in humans

Food intake regulation involves various central and peripheral mechanisms. In this study the relevance of physiological responses reflecting the autonomic nervous system were evaluated in relation to perceived satiety. Subjects were exposed to a lunch-induced hunger-satiety shift, while profiling diverse sensory, physiological, and biochemical characteristics at 15 min intervals. Sensory ratings comprised questionnaires with visual analogues scales about their feeling of satiety, desire to eat, fullness, and hunger. Physiological characteristics included heart rate, heart rate variability, and blood pressure, while biochemical markers such as cortisol levels and α-amylase activity were monitored in saliva. The four sensory ratings correlated with heart rate and salivary α-amylase suggesting a higher sympathetic tone during satiety. Furthermore, heart rate variability was associated with age and waist-to-hip ratio and cortisol levels negatively correlated with body mass index. Finally, neither chewing nor swallowing contributed to a heart rate increase at food consumption, but orosensory stimulation, as tested with modified sham feeding, caused a partial increase of heart rate. In conclusion, after meal ingestion critical physiological alterations reveal a elevated sympathetic tone, which is a potential measure of satiety

Muscle Sympathetic Nerve Activity Is Related to a Surrogate Marker of Endothelial Function in Healthy Individuals

BACKGROUND: Evidence from animal studies indicates the importance of an interaction between the sympathetic nervous system and the endothelium for cardiovascular regulation. However the interaction between these two systems remains largely unexplored in humans. The aim of this study was to investigate whether directly recorded sympathetic vasoconstrictor outflow is related to a surrogate marker of endothelial function in healthy individuals. METHODS AND RESULTS: In 10 healthy normotensive subjects (3 f/7 m), (age 37+/-11 yrs), (BMI 24+/-3 kg/m(2)) direct recordings of sympathetic action potentials to the muscle vascular bed (MSNA) were performed and endothelial function estimated with the Reactive Hyperaemia- Peripheral Arterial Tonometry (RH-PAT) technique. Blood samples were taken and time spent on leisure-time physical activities was estimated. In all subjects the rate between resting flow and the maximum flow, the Reactive Hyperemic index (RH-PAT index), was within the normal range (1.9-3.3) and MSNA was as expected for age and gender (13-44 burst/minute). RH-PAT index was inversely related to MSNA (r = -0.8, p = 0.005). RH-PAT index and MSNA were reciprocally related to time (h/week) spent on physical activity (p = 0.005 and p = 0.006 respectively) and platelet concentration (PLT) (p = 0.02 and p = 0.004 respectively). CONCLUSIONS: Our results show that sympathetic nerve activity is related to a surrogate marker of endothelial function in healthy normotensive individuals, indicating that sympathetic outflow may be modulated by changes in endothelial function. In this study time spent on physical activity is identified as a predictor of sympathetic nerve activity and endothelial function in a group of healthy individuals. The results are of importance in understanding mechanisms underlying sympathetic activation in conditions associated with endothelial dysfunction and emphasise the importance of a daily exercise routine for maintenance of cardiovascular health

Weighted needle pinprick sensory thresholds: a simple test of sensory function in diabetic peripheral neuropathy

A simple device is described, consisting of 12 weighted 23 gauge disposable needles (0.2 to 5.2 g), for testing sensation in busy diabetic clinics. The pinprick sensory threshold (PPT) is the lightest weighted needle which consistently elicits a sharp sensation. The subjects were 48 healthy controls (hospital staff), 44 diabetic patients without neuropathic symptoms, and 35 diabetic patients with chronic painful neuropathy. In the controls, the mean PPT from the right hand and foot obtained on two test occasions a week apart did not differ significantly. In diabetic patients without symptomatic neuropathy, the mean PPT in the right hand and right foot were significantly higher than in the controls. The diabetic patients with painful neuropathy had clearly increased mean PPT in the right hand and foot compared with controls. Marstock thermal limen in diabetic patients with painful neuropathy correlated significantly with PPT determinations. PPT and thermal thresholds probably give comparable information on small fibre dysfunction in diabetic patients with symptomatic neuropathy. Compared with thermal threshold determinations however, the weighted needle apparatus is inexpensive, simple, and rapid to use