Metrics of High Cofluctuation and Entropy to Describe Control of Cardiac Function in the Stellate Ganglion

Neural control of the heart involves dynamic adaptation of mechanical and electrical indices to meet blood flow demands. The control system receives centrally-derived inputs to coordinate cardiac function on a beat-by-beat basis, producing 'functional' outputs such as the blood pressure waveform. Bilateral stellate ganglia (SG) are responsible for integration of multiple inputs and efferent cardiopulmonary sympathetic neurotransmission. In this work, we investigate network processing of cardiopulmonary transduction by SG neuronal populations in porcine with chronic pacing-induced heart failure and control subjects. We derive novel metrics to describe control of cardiac function by the SG during baseline and stressed states from in vivo extracellular microelectrode recordings. Network-level spatiotemporal dynamic signatures are found by quantifying state changes in coactive neuronal populations (i.e., cofluctuations). Differences in 'neural specificity' of SG network activity to specific phases of the cardiac cycle are studied using entropy estimation. Fundamental differences in information processing and cardiac control are evident in chronic heart failure where the SG exhibits: i) short-lived, high amplitude cofluctuations in baseline states, ii) greater variation in neural specificity to cardiac cycles, iii) limited sympathetic reserve during stressed states, and iv) neural network activity and cardiac control linkage that depends on disease state and cofluctuation magnitude. These findings indicate that spatiotemporal dynamics of stellate ganglion neuronal populations are altered in heart failure, and lay the groundwork for understanding dysfunction neuronal signaling reflective of cardiac sympathoexcitation.

Impact of acute partial-body cryostimulation on cognitive performance, cerebral oxygenation, and cardiac autonomic activity

We assessed the effects of a 3-min partial-body cryostimulation (PBC) exposure—where the whole body is exposed to extreme cold, except the head—on cognitive inhibition performance and the possible implications of parasympathetic cardiac control and cerebral oxygenation. In a randomized controlled counterbalanced cross-over design, eighteen healthy young adults (nine males and nine females) completed a cognitive Stroop task before and after one single session of PBC (3-min exposure at − 150 °C cold air) and a control condition (3 min at room temperature, 20 °C). During the cognitive task, heart rate variability (HRV) and cerebral oxygenation of the prefrontal cortex were measured using heart rate monitoring and near-infrared spectroscopy methods. We also recorded the cerebral oxygenation during the PBC session. Stroop performance after PBC exposure was enhanced (562.0 ± 40.2 ms) compared to pre-PBC (602.0 ± 56.4 ms; P < 0.042) in males only, accompanied by an increase (P < 0.05) in HRV indices of parasympathetic tone, in greater proportion in males compared to females. During PBC, cerebral oxygenation decreased in a similar proportion in males and females but the cerebral extraction (deoxyhemoglobin: ΔHHb) remained higher after exposure in males, only. These data demonstrate that a single PBC session enhances the cognitive inhibition performance on a Stroop task in males, partly mediated by a greater parasympathetic cardiac control and greater cerebral oxygenation. The effects of PBC on cognitive function seem different in females, possibly explained by a different sensitivity to cold stimulation.

Acknowledging Sex Differences in In vivo Experiments: Dilemma

The role of the Autonomic Nervous System (ANS) and its organ-specific functions are largely elucidated. Heart Rate Variability (HRV) analysis is a popular tool for the assessment of autonomic cardiac control. Heart rate and its changes are a sensitive indicator of ANS function, therefore cardiovascular autonomic regulation is considered to be the most reliable indicator of ANS activity and status. HRV refers to beat to beat variation in the heart rate that quantifies the interplay between sympathetic and parasympathetic activity of the ANS. Although patterns of HRV hold considerable promise for clarifying issues in clinical applications,

Abstract P227: Psychosocial Predictors of Physical Capacity in Cardiac Rehabilitation

Introduction: Despite the impressive gains achieved by those who attend cardiac rehabilitation, many patients fail to maintain the gains in physical capacity in the longer term. There are likely psychosocial characteristics that can be leveraged to sustain behavior change. Hypothesis: Patients with higher perceived cardiac control, social support, and exercise self-efficacy, without depression, and those who received motivational interviewing (MI) sessions, adjunctive to cardiac rehabilitation, will have a significantly higher physical capacity. Methods: This is a secondary analysis of the data from a randomized controlled trial of MI as a tool to enhance secondary prevention strategies in cardiovascular disease (MICIS study) conducted at three hospitals in Sydney, Australia who attended 6-week phase II cardiac rehabilitation. Two, 1-hour sessions of a nurse-delivered motivational interview focused on increasing physical capacity was implemented and the participants were followed at 6-weeks and 12-months. The outcome for the study was physical capacity measured by distance walked on the six-minute walk test (6MWT). Multiple imputations were used to handle missing data. Descriptive statistics, t-tests, chi-square tests and linear regression for cluster data were used for data analysis. Results: The mean (SD) age of participants (n=110) at baseline was 60.1 (10.57) years and the majority were male (71.8%). (Table). In the adjusted analysis, motivational interviewing (p =0.57), perceived cardiac control (p=0.30), self-efficacy for exercise (p = 0.06) and level of depressive symptoms were not related to 6MWT. With every unit increase in perceived social support score, there was a decrease in distance walked in 6MWT by 1.30 meters (b = -1.30; p= 0.007). Conclusion: In this sample, psychosocial predictors, except social support, were not likely to influence physical capacity. Investigating barriers and facilitators to sustaining the effects of cardiac rehabilitation are needed.