Mechanisms and clinical consequences of untreated central sleep apnea in heart failure

Abstract

Central sleep apnea (CSA) is a highly prevalent, though often unrecognized, comorbidity in patients with heart failure (HF). Data from HF population studies suggest that it may present in 30% to 50% of HF patients. CSA is recognized as an important contributor to the progression of HF and to HF-related morbidity and mortality. Over the past 2 decades, an expanding body of research has begun to shed light on the pathophysiologic mechanisms of CSA. Armed with this growing knowledge base, the sleep, respiratory, and cardiovascular research communities have been working to identify ways to treat CSA in HF with the ultimate goal of improving patient quality of life and clinical outcomes. In this paper, we examine the current state of knowledge about the mechanisms of CSA in HF and review emerging therapies for this disorder.

Keywords: apnea-hypopnea index; continuous positive airway pressure; hypoxia; reactive oxygen species; reoxygenation.

FIGURE 1. Polysomnogram of CSA in a Patient With Heart Failure

Overnight polysomnography performed in a sleep laboratory remains the gold standard for diagnosing sleep-disordered breathing. The image highlights characteristic findings of central sleep apnea (CSA) on a polysomnogram.

CENTRAL ILLUSTRATION. Pathophysiologic Consequences of CSA in Heart Failure

The repeated episodes of apnea, hypoxia, reoxygenation, and arousal throughout the night are the factors leading to the pathophysiologic consequences of central sleep apnea (CSA). These pathologic effects are multiple, and include sympathetic nervous system activation, oxidative stress, systemic inflammation, and endothelial dysfunction. All contribute to worsening heart failure. RAAS = renin-angiotensin aldosterone system.

FIGURE 2. Practical CSA Management in Patients With Heart Failure

Current treatment strategies for central sleep apnea (CSA) focus on either improving heart failure (HF) or reducing CSA itself. ACE-I = angiotensin-converting enzyme inhibitor; OSA = obstructive sleep apnea; SDB = sleep-disordered breathing; Sxs = symptoms.