Novel pulse oximetry-derived measures of obstructive sleep apnoea severity and cardiovascular function in heart failure with preserved ejection fraction patients.

<bold>Introduction:</bold> Obstructive Sleep Apnoea (OSA) is common in Heart Failure with Preserved Ejection Fraction (HFpEF) and OSA treatment may improve outcomes; however, the pathophysiological implications of OSA in HFpEF remain unclear. While novel pulse oximetry-derived measures of cardiovascular risk in OSA have recently been developed, these have not been assessed in HFpEF. <bold>Methods:</bold> This study determined pulse oximetry-derived measures of Hypoxic Burden (HB, cumulative area of respiratory event related SpO2 dips, %min/h) and Pulse-Wave Amplitude Drops Index (PWAD_In, drops in pulse wave amplitude of >30% per hour, events/h) in HFpEF patients with and without moderate-severe OSA (Apnoea-Hypopnoea Index, AHI, ≥15 events/h). Patients underwent comprehensive cardiovascular and polysomnography assessments to examine associations between HB and PWAD_In and cardiovascular function. <bold>Results:</bold> Thirty-two HFpEF patients were assessed (Age 66±13y; BMI 33.5±7.3kg/m2; BNP 209±302ng/L), of which 19 had moderate-severe OSA and 13 had no or mild OSA (AHI<15 events/hr). There were no differences in age, BMI, gender or PWAD_In (53.0±28.2 vs 56.0±25.8 events/h, p=0.760) between groups, while HB (29.0±23.5 vs 104.3±73.8 %min/h, p<0.001) was higher in moderate-severe OSA. PWAD_In correlated with left ventricular (LV) ejection fraction (R=-0.618, p=0.006), while HB correlated with right ventricular (RV) end-diastolic volume (R=0.445, p=0.014) and aortic augmentation index (R=0.510, p=0.003). <bold>Conclusions:</bold> These preliminary data indicate that HB and PWAD_In may provide additional insight into the severity and pathophysiological implications of OSA in HFpEF. The influence of recurrent overnight oxygen desaturations and pulse wave amplitude drops on LV and RV remodelling in HFpEF requires further mechanistic study.