Abstract 1639: Relationship between Overnight Rostral Fluid Shift and Sleep Apnea in Heart Failure
Sleep apnea is commoner in heart failure (HF) patients, a fluid retaining state, than in those without HF. In HF patients, fluid displaced from the legs while recumbent could accumulate in the neck and predispose to obstructive sleep apnea (OSA), or in the lungs and predispose to central sleep apnea (CSA). We hypothesized that in HF patients: severity of sleep apnea will be related to the amount of spontaneous overnight rostral fluid shift from the legs, and progressively greater amounts of fluid shift will be associated with a gradation from no sleep apnea (NSA), to OSA, to CSA. In HF patients (ejection fraction ≤45%), we assessed change in fluid volume of one leg (LFV) using bioelectrical impedance, and in neck circumference (NC) before and after an overnight sleep study. Patients were classified as having NSA (apnea-hypopnea index [AHI] < 10/hr of sleep) or sleep apnea (AHI ≥ 10/hr of sleep), subclassified into OSA (≥50% obstructive events) or CSA (> 50% central events). In 30 patients (mean ± SD 58 ± 13 yr, body mass index 30.4 ± 4.2 kg/m2) the overnight change in LFV was −256 ± 165 ml. The AHI correlated inversely with the overnight change in LFV (r = −0.84, p < 0.001, Figure⇓), and the change in NC (r = −0.76, p < 0.001). In a multivariate analysis the significant independent correlates of the AHI were the change in LFV and change in NC which explained 76% of variability in AHI. Progressively greater decreases in LFV were accompanied by a gradation from NSA, to OSA, to CSA (−78 ± 15, to −245 ± 41, to −433 ± 59 ml, respectively, Ptrend < 0.001). In HF, spontaneous overnight rostral fluid displacement from the legs contributes to both the severity and type of sleep apnea.