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. METHODS: To determine whether daytime QT intervals in OSA patients are prolonged compared to control subjects, we recruited 97 (76 male, 21 female) newly diagnosed patients with OSA [apnea-hypopnea index (AHI) ≥5 events/h] and 168 (100 male, 68 female) healthy volunteers (AHI <5 events/h) and measured daytime resting QT and RR intervals from the electrocardiograms to determine QT prolongation corrected for heart rate (QTc). RESULTS: All subjects with OSA were older and heavier, with increased heart rate, significantly increased AHI and arousal index, and reduced oxygen saturation (SpO2) during sleep, and spent less time in sleep with >90 % SpO2 compared to respective controls. QTc in patients with OSA (410 ± 3.3 for male and 433 ± 5.6 for female) was significantly increased compared to respective control groups (399 ± 2.9 for male and 417 ± 2.9 for female), after adjustment for age and body mass index. CONCLUSIONS: Our data show that OSA in either men or women is associated with a significant increase in resting daytime QTc. The propensity for ventricular arrhythmias in patients with OSA may be a result of abnormalities in resting cardiac repolarization.

Obstructive sleep apnea and hypertension.

There has long been a recognized link between obstructive sleep apnea (OSA) and the cardiovascular system, no aspect of which has been more studied than blood pressure. Research in OSA has not only demonstrated dysregulation of homeostatic cardiovascular mechanisms but also has furthered our understanding of blood pressure regulatory control. Acute nocturnal blood pressure elevations associated with disordered breathing events have been reproduced from a number of observational studies, the accrual of which has also made an increasing argument for the importance of OSA in the pathogenesis of diurnal hypertension, as suggested by the Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure (JNC 7), which implicated OSA as a secondary cause of hypertension. Accumulating data from randomized controlled treatment trials in OSA, particularly with continuous positive airway pressure, though sometimes inconsistent, suggest a potential role in blood pressure reduction. Further research is needed to better clarify indications for OSA treatment as well as its role as an adjunct to other antihypertensive treatments.

Relationships between leptin and C-reactive protein with cardiovascular disease in the adult general population.

BACKGROUND: Leptin could be a key regulator of C-reactive protein (CRP) levels, which serve as a marker of systemic inflammation. Both leptin and CRP are predictors of cardiovascular disease (CVD). However, the interactions between leptin and CRP, and their association with CVD, remain unclear. We therefore studied them in a large, multiethnic population. METHODS: We analyzed leptin and CRP levels, anthropometric variables and cardiovascular risk factor data from 6,251 participants from the Third National Health and Nutrition Examination Survey (NHANES III). Logistic regression was used to estimate the association between leptin, CRP and CVD (defined as history of myocardial infarction or stroke). Receiver operating characteristic curves were created to study the additional value of leptin and CRP for the association with CVD. RESULTS: The mean age was 44.4 +/- 0.21 years (52.5% women). After adjustment for age, race, dyslipidemia, hypertension, diabetes, smoking, obesity and CRP, high levels of leptin were significantly associated with CVD in men (odds ratio 2.47, 95% CI 1.19-5.19) and in women (odds ratio 3.30, 95% CI 1.47-7.99). After adjustment for leptin, CRP was not associated with CVD. There was a significant correlation between levels of leptin and CRP (Spearman correlation rho = 0.22 in men and rho = 0.32 in women, both P < 0.0001). The area under the curve, representing the association between cardiovascular risk factors and CVD, increased after the addition of high levels of both leptin and CRP together. CONCLUSION: High leptin levels are independently associated with CVD even after adjustment for CRP; elevated CRP levels are not associated with CVD after adjustment for leptin. However, increased concentrations of both leptin and CRP confer the highest risk for CVD.