Study objective: To assess the possible relationship between Cheyne-Stokes respiration (CSR) associated with central sleep apnea (CSA) syndrome and brain natriuretic peptide (BNP) in an outpatient population presenting with stable congestive heart failure (CHF).
Measurements and results: Ninety patients with CHF due to systolic dysfunction (left ventricular ejection fraction ≤ 45%) were prospectively studied. Each patient underwent conventional polysomnography to establish the diagnosis of CSR-CSA and determination of the BNP level. The correlation between BNP levels and the apnea-hypopnea index (AHI) and desaturation index (DI) was evaluated, as was the accuracy of BNP in identifying CHF-associated CSR-CSA, as determined by the area under the receiver operating characteristic (ROC) curve. Possible confounding variables were assessed, and a stepwise multiple regression analysis was applied to identify those factors that best predicted the variability in BNP levels. Five of the 90 patients were excluded from the study as they presented with obstructive sleep apnea syndrome. Of the remaining 85 patients, 25 (28%) presented with associated CSR-CSA. The mean (±SEM) BNP level was higher in this group (166.44 ± 29.6 pg/mL) than in the group with isolated CHF (62.01 ± 13.6 pg/mL; p < 0.001). There was a moderate correlation between BNP levels and AHI. The ROC curve that best identified CSR-CSA was obtained with a BNP cutoff value of 116.25 pg/mL (sensitivity, 62%; specificity, 92%; accuracy, 83%). Differences between the two groups in terms of BNP levels persisted after adjusting for the confounding variables that were analyzed. Only AHI and DI were independently related to the BNP level, and both explain the 30.5% variability.
Conclusion: Patients with CHF and CSR-CSA have higher BNP levels than those without CSR-CSA. Our results suggest that CSR-CSA and BNP levels are related. However, the possibility that both factors might be independent expressions of the functional status of CHF patients cannot be ruled out.