Neck Chamber Technique Revisited: Low-Noise Device Delivering Negative and Positive Pressure and Enabling Concomitant Carotid Artery Imaging With Ultrasonography

Computational modelling of cardiac control following myocardial infarction using an in silico patient cohort

Loss of cardiac physiological function following myocardial infarction (MI) is accompanied by neural adaptations in the baroreflex that are compensatory in the short term, but then become associated with long-term disease progression. One marker of these adaptations is decreased baroreflex sensitivity, a strong predictor of post-MI mortality. The relative contributions of cardiac remodelling and neural adaptation in the sensory, central brainstem and peripheral ganglionic loci to baroreflex sensitivity changes remain underexplored. We used a computational model-based approach that accounts for the short-term dynamics of closed-loop human cardiac control to integrate disparate experimental studies on neural adaptation following MI into a unified quantitative framework. We developed an ensemble of 59 distinct model parameterizations that account for the clinically observed heterogeneity of cardiac control in healthy individuals. We simulated an in silico cohort of 35,400 patients with MI, corresponding to six scenarios of one or more loci of neural adaptation coupled with cardiac remodelling. We evaluated the range of MI-induced shifts in arterial pressure, heart rate and baroreflex curve responses. Our results show that adaptation in any single neural locus coupled with cardiac remodelling is sufficient to account for the MI-induced haemodynamic and autonomic changes observed experimentally. Of the adaptation pathways, we found that individuals with central or peripheral vagal efferent adaptation and preserved baroreceptor gain could maintain high baroreflex sensitivity after ischaemic injury. These results suggest that there are a multitude of adaptive pathways for tuning the baroreflex circuit to shift cardiac control physiology, potentially explaining patient heterogeneity post-MI. KEY POINTS: Baroreflex sensitivity is a strong indicator of post-myocardial ischaemia survival and is variable among individuals. We fine-tuned a computational model ensemble based on physiological observations to develop an in silico patient cohort consistent with the range of baroreflex responses observed experimentally. Simulation and analysis of the in silico cohort show that individuals with a functional afferent pathway and the ability to adapt along the vagal efferent pathway can maintain baroreflex sensitivity post-cardiac ischaemia.

Squeeze the beat: Enhancing cardiac vagal activity during resonance breathing via coherent pelvic floor recruitment

Resonance breathing (RB) has been shown to benefit health and performance within clinical and non-clinical populations. This is attributed to its baroreflex stimulating effect and the concomitant increase in cardiac vagal activity (CVA). Hence, developing methods that strengthen the CVA boosting effect of RB could improve its clinical effectiveness. Therefore, we assessed whether supplementing RB with coherent pelvic floor activation (PRB), which has been shown to entrain the baroreflex, yields stronger CVA than standard RB. N = 32 participants performed 5-min of RB and PRB, which requires to recruit the pelvic floor during the complete inspiratory phase and release it at the initiation of the expiration. CVA was indexed via heart rate variability using RMSSD and LF-HRV. PRB induced significantly larger RMSSD (d = 1.04) and LF-HRV (d = 0.75, ps < .001) as compared to RB. Results indicate that PRB induced an additional boost in CVA relative to RB in healthy individuals. However, subsequent studies are warranted to evaluate whether these first findings can be replicated in individuals with compromised health, including a more comprehensive psychophysiological assessment to potentially elucidate the origin of the observed effects. Importantly, longitudinal studies need to address whether PRB translates to better treatment outcomes.