Introduction: Neuropeptides arginine-vasopressin (AVP), apelin (APL), and stromal-derived factor-1α (SDF-1α) are involved in the dysfunction of the corticotropic axis observed in septic ICU patients. Study aims were: (i) to portray a distinctive stress-related neuro-corticotropic systemic profile of early sepsis, (ii) to propose a combination data score, for aiding ICU physicians in diagnosing sepsis on admission. Methods: This prospective one-center observational study was carried out in a medical intensive care unit (MICU), tertiary teaching hospital. Seventy-four out of 112 critically ill patients exhibiting systemic inflammatory response syndrome (SIRS) were divided into two groups: proven sepsis and non sepsis, based on post hoc analysis of microbiological criteria and final diagnosis, and compared to healthy volunteers (n = 14). A single blood sampling was performed on admission for measurements of AVP, copeptin, APL, SDF-1α, adrenocorticotropic hormone (ACTH), cortisol baseline and post-stimulation, and procalcitonin (PCT). Results: Blood baseline ACTH/cortisol ratio was lower and copeptin higher in septic vs. nonseptic patients. SDF-1α was further increased in septic patients vs. normal patients. Cortisol baseline, ACTH, PCT, APACHE II and sepsis scores, and shock on admission, were independent predictors of sepsis diagnosis upon admission. Using the three first aforementioned categorical bio-parameters, a probability score for predicting sepsis yielded an area under the Receiver Operating Curve (ROC) curves better than sepsis score or PCT alone (0.903 vs 0.727 and 0.726: P = 0.005 and P < 0.04, respectively). Conclusions: The stress response of early admitted ICU patients is different in septic vs. non-septic conditions. A proposed combination of variable score analyses will tentatively help in refining bedside diagnostic tools to efficiently diagnose sepsis after further validation.

Background—: Arrhythmias associated with QT prolongation on the ECG often lead to sudden unexpected death in epilepsy. The mechanism causing a prolongation of the QT interval during epilepsy remains unknown. Based on observations showing an upregulation of neuronal sodium channels in the brain during epilepsy, we tested the hypothesis that a similar phenomenon occurs in the heart and contributes to QT prolongation by altering cardiac sodium current properties (I _Na ). Methods and Results—: We used the patch clamp technique to assess the effects of epilepsy on the cardiac action potential and I _Na in rat ventricular myocytes. Consistent with QT prolongation, epileptic rats had longer ventricular action potential durations attributable to a sustained component of I _Na (I _NaL ). The increase in I _NaL was because of a larger contribution of neuronal Na channels characterized by their high sensitivity to tetrodotoxin. As in the brain, epilepsy was associated with an enhanced expression of the neuronal isoform Na _V 1.1 in cardiomyocyte. Epilepsy was also associated with a lower I _Na activation threshold resulting in increased cell excitability. Conclusions—: This is the first study correlating increased expression of neuronal sodium channels within the heart to epilepsy-related cardiac arrhythmias. This represents a new paradigm in our understanding of cardiac complications related to epilepsy.

Functional alterations in the properties of Aβ afferent fibers may account for the increased pain sensitivity observed under peripheral chronic inflammation. Among the voltage-gated sodium channels involved in the pathophysiology of pain, Nav1.8 has been shown to participate in the peripheral sensitization of nociceptors. However, to date, there is no evidence for a role of Nav1.8 in controlling Aβ-fiber excitability following persistent inflammation.

Brugada syndrome has been linked to mutations in SCN5A. Agents that dissociate slowly from the sodium channel such as flecainide and ajmaline unmask the Brugada syndrome electrocardiogram and precipitate ventricular tachycardia/fibrillation. Lidocaine, an agent with rapid dissociation kinetics, has previously been shown to exert no effect in patients with Brugada syndrome. We characterized a novel double mutation of SCN5A (V232I in DI-S4+L1308F in DIII-S4) identified in a rare case of lidocaine (1 mg/kg)-induced Brugada syndrome. We studied lidocaine blockade of I _Na generated by wild-type and V232I+L1308F mutant cardiac sodium channels expressed in mammalian TSA201 cells using patch clamp techniques. Despite no significant difference in steady-state gating parameters between V232I+L1308F and wild-type sodium currents at baseline, use-dependent inhibition of I _Na by lidocaine was more pronounced in V232I+L1308F versus wild-type (73.0±0.1% versus 18.23±0.04% at 10 μmol/L measured at 10 Hz, respectively). A dose of 10 μmol/L lidocaine also caused a more negative shift of steady-state inactivation in V232I+L1308F versus wild-type (−14.1±0.3 mV and −4.8±0.3 mV, respectively). The individual mutations produced a much less accentuated effect. We report the first case of lidocaine-induced Brugada electrocardiogram phenotype. The double mutation in SCN5A, V232I, and L1308F alters the affinity of the cardiac sodium channel for lidocaine such that the drug assumes Class IC characteristics with potent use-dependent block of the sodium channel. Our results demonstrate an additive effect of the 2 missense mutations to sensitize the sodium channel to lidocaine. These findings suggest caution when treating patients carrying such genetic variations with Class I antiarrhythmic drugs.

Women have a higher incidence of long QT-related arrhythmias, whereas men exhibit a higher incidence of Brugada syndrome (BrS). The cardiac sodium current (I_Na) is associated with arrhythmias in BrS and long QT-syndrome (LQTS) and conduction disease. Although a great deal of work has been performed to explain how heterogeneous distribution of repolarizing currents triggers arrhythmias, the transmural distribution of I_Na within the cardiac ventricle and its contribution to generate the arrhythmogenic substrate remain unknown. We undertook to determine whether I_Na was heterogeneously distributed within the ventricular wall of canine heart, an animal model close to humans. Using patch-clamp and molecular biology techniques, we tested whether gender differences exist in the ventricular distribution and amplitude of I_Na in the canine heart model. Our results show that the I_Na amplitude is smaller in the female epicardial and endocardial layers of the left ventricle, but similar to male in the mid-myocardium. Exposure of female cardiomyocytes to testosterone increased the amplitude of I_Na to levels similar to male in epicardium, but had no effects in mid-myocardial and endocardial cells. Castrated male dogs displayed I_Na amplitudes similar to what was found in female hearts. The larger dispersion of I_Na amplitude within the female cardiac ventricle may contribute to the higher risk of arrhythmias in females. Testosterone modulates this dispersion. By decreasing the transmural dispersion of I_Na, testosterone may exert a protective effect against LQTS-related arrhythmias in males.