Daytime cardiac repolarization in patients with obstructive sleep apnea.

Purpose: Obstructive sleep apnea (OSA) has been implicated in complications of cardiovascular disease, including arrhythmias and sudden cardiac death (SCD). Prolonged QT interval is associated with arrhythmias and SCD in patients with cardiovascular disease and apparently healthy humans. Apneic episodes during sleep in OSA patients are associated with QT prolongation due to increased vagal activity, but it is not understood whether chronic QT prolongation persists during normoxic daytime wakefulness.

Leptin deficiency promotes central sleep apnea in patients with heart failure.

Background: Leptin-deficient animals hyperventilate. Leptin expression by adipocytes is attenuated by atrial natriuretic peptide (ANP). Increased circulating natriuretic peptides (NPs) are associated with an increased risk of central sleep apnea (CSA).

Effects of experimental sleep restriction on caloric intake and activity energy expenditure.

Background: Epidemiologic studies link short sleep duration to obesity and weight gain. Insufficient sleep appears to alter circulating levels of the hormones leptin and ghrelin, which may promote appetite, although the effects of sleep restriction on caloric intake and energy expenditure are unclear. We sought to determine the effect of 8 days/8 nights of sleep restriction on caloric intake, activity energy expenditure, and circulating levels of leptin and ghrelin.

Relation of natriuretic peptide concentrations to central sleep apnea in patients with heart failure.

Background: Central sleep apnea (CSA) is frequent among patients with heart failure (HF) and associated with increased morbidity and mortality. Elevated cardiac filling pressures promote CSA and atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) secretion. We hypothesized that circulating natriuretic peptide concentrations predict CSA.

Diagnostic accuracy of the Berlin Questionnaire in detecting sleep-disordered breathing in patients with a recent myocardial infarction.

Background: The Berlin Questionnaire (BQ) has been used to identify patients at high risk for sleep-disordered breathing (SDB) in a variety of populations. However, there are no data regarding the validity of the BQ in detecting the presence of SDB in patients after myocardial infarction (MI). The aim of this study was to determine the performance of the BQ in patients after MI.

Effect of weight gain on cardiac autonomic control during wakefulness and sleep.

Obesity has been associated with increased cardiac sympathetic activation during wakefulness, but the effect on sleep-related sympathetic modulation is not known. The aim of this study was to investigate the effect of fat gain on cardiac autonomic control during wakefulness and sleep in humans. We performed a randomized, controlled study to assess the effects of fat gain on heart rate variability.

Patients with obstructive sleep apnea exhibit impaired endothelial function after myocardial infarction.

Background: Impaired brachial flow-mediated dilation (FMD) is associated with risk for subsequent cardiovascular events in patients after myocardial infarction (MI). These patients often have obstructive sleep apnea (OSA). We tested the hypothesis that patients with OSA post MI will exhibit more severe impairment in FMD.

Sleep-disordered breathing in patients with the Brugada syndrome.

We investigated breathing patterns and the occurrence of arrhythmias and ST-segment changes during sleep in patients with Brugada syndrome. Patients with Brugada syndrome are more likely to die from ventricular arrhythmias during sleep. ST-segment changes have been correlated with risk of sudden cardiac death.

Diagnostic accuracy of split-night polysomnograms.

Study Objectives: American Academy of Sleep Medicine (AASM) practice parameters indicate that split-night polysomnograms (SN-PSG) may be performed when the apnea hypopnea index (AHI) is > or = 20 to 40, depending on clinical factors. The aim of this study was to determine the diagnostic accuracy of SN-PSG, including at the lower range of AHIs.

Methods: We reviewed 114 consecutive full-night PSGs (FN-PSG) performed at our center between August 2006 and November 2008 on subjects enrolled in studies in which obstructive sleep apnea (OSA) was the sleep disorder of interest.

Advanced heart failure and nocturnal hypoxaemia due to central sleep apnoea are associated with increased serum erythropoietin.

Aims: Central sleep apnoea (CSA) and increased serum erythropoietin (EPO) concentration have each been associated with adverse prognosis in heart failure (HF) patients. The aim of this study was to examine the relationship between nocturnal hypoxaemia due to CSA and the serum EPO concentration in patients with HF.

Methods And Results: Heart failure subjects (n = 33) and healthy controls (n = 18) underwent polysomnography (PSG) for diagnosis of CSA and identification and quantification of hypoxaemia.

Day-night variation of acute myocardial infarction in obstructive sleep apnea.

Objectives: This study sought to evaluate the day-night variation of acute myocardial infarction (MI) in patients with obstructive sleep apnea (OSA).

Background: Obstructive sleep apnea has a high prevalence and is characterized by acute nocturnal hemodynamic and neurohormonal abnormalities that may increase the risk of MI during the night.

Methods: We prospectively studied 92 patients with MI for which the time of onset of chest pain was clearly identified.

Standardization criteria for an ischemic surgical model of acute hepatic failure in pigs.

The establishment of a reliable large animal model of acute hepatic failure (AHF) is critical for the evaluation of supportive therapies such as bioartificial liver support systems (BALSS). Large animal surgical models bear some resemblance to the clinical syndrome of AHF in humans. However, these are inherently complex and are predisposed to inter-individual variation.