QTc interval in survivors of out of hospital cardiac arrest.

BACKGROUND: QTc interval (QTc) prolongation is seen on the post-arrest electrocardiogram (ECG) of many out of hospital cardiac arrest (OHCA) survivors. It remains unclear whether this is a transient phenomenon or a manifestation of an underlying arrhythmic substrate. This observational study assessed the trend of QTc in an unselected group of patients presenting with OHCA. We sought to identify any relationship between QTc, gender and aetiology of arrest. We observed whether targeted temperature management (TTM) is associated with malignant arrhythmia. METHOD: We analysed 60 patients presenting with OHCA to the Bristol Heart Institute during a 20-month period. We measured QTc on admission and assessed for persistence, development and resolution of prolongation at up to 5 time points post-OHCA. Aetiology of arrest was divided into coronary, non-coronary or primary arrhythmic to investigate for patterns in QTc behaviour. RESULTS: 81.7% (49/60) of arrests were attributed to an acute coronary event. 55% (33/60) had QTc prolongation on admission, of which 79% resolved. There were no significant differences in QTc behaviour by aetiology. One patient presenting with a normal QTc, developed prolongation during admission and received a genetic diagnosis of Long QT Syndrome. TTM was employed in 57/60, with no increased incidence of malignant arrhythmia. CONCLUSIONS: Prolonged QTc on admission does not imply a primary arrhythmic aetiology and resolves in the majority pre-discharge. However, an initial normal QTc post-OHCA does not preclude a diagnosis of Long QT syndrome, highlighting the importance of thorough investigations in these patients. TTM appears safe from a cardiac perspective.

Day-night differences in neural activation in histaminergic and serotonergic areas with putative projections to the cerebrospinal fluid in a diurnal brain.

In nocturnal rodents, brain areas that promote wakefulness have a circadian pattern of neural activation that mirrors the sleep/wake cycle, with more neural activation during the active phase than during the rest phase. To investigate whether differences in temporal patterns of neural activity in wake-promoting regions contribute to differences in daily patterns of wakefulness between nocturnal and diurnal species, we assessed Fos expression patterns in the tuberomammillary (TMM), supramammillary (SUM), and raphe nuclei of male grass rats maintained in a 12:12 h light-dark cycle. Day-night profiles of Fos expression were observed in the ventral and dorsal TMM, in the SUM, and in specific subpopulations of the raphe, including serotonergic cells, with higher Fos expression during the day than during the night. Next, to explore whether the cerebrospinal fluid is an avenue used by the TMM and raphe in the regulation of target areas, we injected the retrograde tracer cholera toxin subunit beta (CTB) into the ventricular system of male grass rats. While CTB labeling was scarce in the TMM and other hypothalamic areas including the suprachiasmatic nucleus, which contains the main circadian pacemaker, a dense cluster of CTB-positive neurons was evident in the caudal dorsal raphe, and the majority of these neurons appeared to be serotonergic. Since these findings are in agreement with reports for nocturnal rodents, our results suggest that the evolution of diurnality did not involve a change in the overall distribution of neuronal connections between systems that support wakefulness and their target areas, but produced a complete temporal reversal in the functioning of those systems.