Left Atrial size, chemosensitivity, and central sleep apnea in heart failure

BACKGROUND: Central sleep apnea (CSA) is common among patients with heart failure (HF) and is promoted by elevated CO₂ chemosensitivity. Left atrial size is a marker of the hemodynamic severity of HF. The aim of this study was to determine if left atrial size predicts chemosensitivity to CO ₂ and CSA in patients with HF. METHODS: Patients with HF with left ventricular ejection fraction ≥ 35% underwent polysomnography for detection of CSA, echocardiography, and measurement of CO₂ chemosensitivity. CSA was defined as an apnea-hypopnea index (AHI) ≥ 15/h with ≥ 50% central apneic events. The relation of clinical and echocardiographic parameters to chemosensitivity and CSA were evaluated by linear regression, estimation of ORs, and receiver operator characteristics. RESULTS: Of 46 subjects without OSA who had complete data for analysis, 25 had CSA. The only parameter that significantly correlated with chemosensitivity was left atrial volume index (LAVI) ( r = 0.40, P < .01). LAVI was greater in those with CSA than those without CSA (59.2 mL/m₂ vs 36.4 mL/m₂ , P < .001) and significantly correlated with log-transformed AHI ( r = 0.46, P = .001). LAVI was the best predictor of CSA (area under the curve = 0.83). A LAVI ≥ 33 mL/m² was associated with 22% risk for CSA, while LAVI ≥ 53 mL/m² was associated with 92% risk for CSA. CONCLUSIONS: Increased LAVI is associated with heightened CO₂ chemosensitivity and greater frequency of CSA. LAVI may be useful to guide referral for polysomnography for detection of CSA in patients with HF.