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In obstructive sleep apnoea (OSA), recurrent episodes of transient asphyxia or increased effort of breathing against a partially obstructed glottis have been shown to increase the sympathomimetic outflow. There is a consequent absence of the customary reduction in systemic blood pressure and heart rate during sleep and an elevation of daytime systolic blood pressure, possibly contributing to progression of heart failure. The prevalence of sleep disordered breathing among patients with heart failure is of the order of 11–37%, and treatment of this condition with continuous positive airway pressure (CPAP) is likely to improve cardiovascular function and consequently reduce morbidity and mortality.
In this Canadian study 24 middle aged patients with optimally (pharmacologically) managed heart failure (left ventricular ejection fraction (LVEF) <48% by echocardiography) and asymptomatic OSA (Epworth sleepiness scale score <6/24, >20 apnoea/hypopnoeas per hour; at least 50% obstructive from polysomnography) were randomly assigned to receive CPAP or to remain on optimal pharmacological treatment (controls). One month later there was evidence of an 8% increase in LVEF and a 10 mm Hg reduction in the daytime systolic blood pressure in the CPAP group while diastolic blood pressure remained unchanged. These changes were significantly different from the control group.
The authors conclude that heart failure patients (ischaemic or non-ischaemic) with sleep disordered breathing (although asymptomatic) may benefit from the adjunctive use of CPAP. The impact of this modest increase in LVEF on patients’ symptoms, health related quality of life, and mortality needs to be established in larger multicentre trials and with longer term treatment before it can be recommended to the large population of patients with heart failure.
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