ABSTRACT
Sleep-disordered breathing, including obstructive and central sleep apnea (OSA and CSA), is highly prevalent in subjects with left ventricular systolic and diastolic dysfunction, whether asymptomatic or with symptomatic heart failure (HF). Polysomnographic studies enrolling large numbers of consecutive patients with HF have shown that 52% of those with reduced ejection fraction (HFrEF) and 48% of those with preserved ejection fraction (HFpEF) suffer from either OSA or CSA, although the two subtypes are commonly present. Thus, polysomnographic phenotype of the sleep-disordered breathing varies considerably among various studies with either OSA or CSA being the predominant phenotype. Acute pathobiological consequences of sleep apneas and hypopneas include altered blood gases, increased sympathetic activity, sleep fragmentation, and large negative swings in intrathoracic pressure, the latter related to pulmonary congestion and reduced respiratory system compliance associated with left ventricular dysfunction and HF. These sequelae are qualitatively similar in both types of sleep apneas, though more pronounced in OSA than in CSA. Consequent to night after night exposure to the aforementioned acute pathological consequences of sleep apnea, oxidative stress, inflammation, sustained increased sympathetic activity, and endothelial dysfunction ensue. Not surprisingly, therefore, multiple observational studies have shown that SDB is independently associated with excess hospitalization and mortality. Yet, the two randomized clinical trials (RCTs) with positive airway pressure (PAP) devices for treatment of CSA have been neutral, and no RCT has been performed in OSA in HF patients. A second RCT with an adaptive servoventilation device with updated algorithm is in progress. In addition to PAP therapies, transvenous phrenic nerve stimulation has been approved for the treatment of CSA with promising results. Unfortunately, a Phase 3 NIH-funded RCT using nocturnal oxygen for treatment of CSA in HFrEF has been terminated due to inadequate enrollment during COVID-Sars 2 epidemic.
