Atrial fibrillation (AF) is more common in those with obstructive sleep apnea (OSA) than in unaffected individuals and recurs more frequently in the presence of severe OSA after electrical cardioversion and AF ablation. However, it is unknown whether severity of OSA influences the efficacy of anti-arrhythmic drug (AAD) therapy in patients with OSA and AF. This study examined the impact of OSA severity on treatment of symptomatic AF with AADs. We studied 61 patients (62 ± 15 years; 21 women) treated with AADs for symptomatic AF who had overnight polysomnography. Rhythm control was prospectively defined as successful if a patient remained on the same AAD therapy for a minimum of 6 months with ≥75% reduction in symptomatic AF burden. Twenty-four patients (40%) had severe OSA. Thirty patients (49%) were rhythm controlled with AADs. Non-responders to AADs were more likely to have severe OSA than milder disease (52% vs 23%; p < 0.05); those with severe OSA were less likely to respond to AADs than participants with non-severe OSA (39% vs 70%; p = 0.02). Non-responders had higher apnea-hypopnea indices than responders (34 ± 25 vs 22 ± 18 events/hour; p = 0.05), but there were no differences between these groups in minimum oxygen saturation or % time spent in REM sleep. In conclusion, patients with severe OSA are less likely to respond to AAD therapy for AF than those with milder forms of OSA.
Patients with Postural Tachycardia Syndrome (POTS) have excessive orthostatic tachycardia (>30 bpm) when standing from a supine position. Heart rate (HR) and blood pressure (BP) are known to exhibit diurnal variability, but the role of diurnal variability in orthostatic changes of HR & BP is not known. In this study, we tested the hypothesis that there is diurnal variation of orthostatic HR & BP in patients with POTS and healthy controls. Patients with POTS (n=54) and healthy volunteers (n=26) were admitted to the Clinical Research Center. Supine and standing (5 min) HR & BP were obtained on the evening on the day of admission and in the following morning. Overall, standing HR was significantly higher in the morning than the evening (102±3 bpm [AM] vs. 93±2 bpm [PM]; P<0.001). Standing HR was higher in the morning in both POTS patients (108±4 bpm [AM] vs. 100±3 bpm [PM]; P=0.012) and controls (89±3 bpm [AM] vs. 80±2 bpm [PM]; P=0.005), when analyzed separately. There was no diurnal variability in orthostatic BP in POTS. More subjects met the POTS HR criterion in the morning compared with the evening (P=0.008). There was significant diurnal variability in orthostatic tachycardia, with a great orthostatic tachycardia in the morning compared to the evening in both patients with POTS and healthy subjects. Given the importance of orthostatic tachycardia in diagnosing POTS, this diurnal variability should be considered in the clinic as it may affect the diagnosis of POTS.
During differentiation, neuroendocrine cells acquire highly amplified capacities to synthesize neuropeptides to overcome dilution of these signals in the general circulation. Once mature, the normal functioning of integrated physiological systems requires that neuroendocrine cells remain plastic to dramatically alter neuropeptide expression for long periods in response to hormonal and electrical cues. The mechanisms underlying the long-term regulation of neuroendocrine systems are poorly understood. Here we show that the Drosophila basic helix-loop-helix protein DIMM, a critical regulator of neuroendocrine cell differentiation, controls secretory capacity in mature neurons. DIMM expression began embryonically but persisted in adults. Through spatial and temporal manipulation of transgene expression in vivo, we defined two phases of prosecretory DIMM activity. During an embryonic critical window, DIMM controlled the differentiation of amplified expression of the neuropeptide leucokinin. At the onset of metamorphosis, levels of DIMM decreased in the insulin-producing cells (IPCs) in parallel with a marked reduction in levels of Drosophila insulin-like peptide 2 and a key neuropeptide biosynthetic enzyme peptidylglycine ␣-monooxygenase (PHM). Overexpression of DIMM in the IPCs prevented the decrease in PHM levels at this stage. In addition, transient overexpression of DIMM in adults produced a dramatic increase in PHM levels in numerous neurons located throughout the brain. These findings provide insights into the mechanisms controlling the maintenance of differentiated cell states, and they suggest an effective means for dynamically adjusting the strength of hormonal signals in diverse homeostatic systems.
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