Sleep disordered breathing – A hidden co-morbidity in patients with atrial fibrillation?

The association between atrial fibrillation (AF) and sleep disordered breathing is relatively unknown. Sleep disordered breathing includes obstructive sleep apnoea and central sleep apnoea, revealed as isolated and/or sometimes simultaneous disorders. The Apnoea-Hypopnoea Index (AHI) is used to grade sleep disordered breathing into three severity levels; mild (AHI 5–14); moderate (AHI 15–30); severe sleep disordered breathing (AHI >30).1 In the normal population, the occurrence of sleep disordered breathing varies according to severity, gender and age. Central sleep apnoea can in many cases occur as a consequence of cardiovascular disease.2 In other words, the prevalence of sleep disordered breathing in patients with different types of cardiovascular diseases (e.g. hypertension, heart failure, ischaemic heart disease and stroke), is significantly higher compared to patients without cardiovascular disease.2 It is also estimated that sleep disordered breathing is highly prevalent in patients with AF. Arias and Baranchuk3 showed that nearly half of their AF population had obstructive sleep apnoea. However, it may be difficult to diagnose sleep disordered breathing in patients with AF. Moreover, the management of AF in itself is complex, given the fact that AF is not only a heart rhythm disturbance, but foremost a vascular disease. Overlapping symptoms (e.g. palpitations, dyspnoea, nocturia, fatigue or daytime sleepiness) occur, which complicates the diagnostic process, and sleep disordered breathing might therefore be missed in patients with both AF and sleep disordered breathing. It has been demonstrated that sleep disordered breathing, and especially severe untreated obstructive sleep apnoea, increase morbidity and mortality in cardiovascular diseases4 and thus contribute to both occurrence and recurrence of AF.5 It is therefore obvious that the awareness among healthcare professionals regarding the importance of detecting sleep disordered breathing in general and – in line with the scope of this paper – in AF specifically should be increased. This editorial aims to contribute to awareness improvement by presenting necessary knowledge topics and practical management issues. It is known that obstructive sleep apnoea increases the risk of new or recurrent episodes of AF due to mechanical, haemodynamic and neurohormonal changes that stress the heart.6 Negative intrathoric pressure induced by inspiratory efforts during apnoea’s increase afterload reduces cardiac output. Left atrial stretch is caused by surges in blood pressure during apnoeic episodes as a result of increased sympathetic tone. Intermittent nocturnal hypoxemia and hypercapnia induces a complex cascade of physiological processes including increased oxidative stress, inflammation and sympathetic activity, which can cause left atrial remodelling and fibrosis.7 The network of inflammation, obesity, oxidative stress, sympathetic activity and sleep fragmentation predisposes to endothelial dysfunction, which, in turn, can accelerate the progress of atherosclerosis.5 The overall pathophysiological effects of obstructive sleep apnoea can also trigger central sleep apnoea. The embedded effects of central sleep apnoea are in many cases the same as those of obstructive sleep apnoea and create a vicious circle, which increases occurrence of central sleep apnoea.2,8 Sleep disordered breathing can be considered as a treatable co-morbidity in patients with AF. However, the guidelines on the management of AF only briefly mention the relationship between AF and sleep disordered breathing and do not provide any detailed recommendation on how to identify patients and set a medical diagnosis.9 Detection of signs and symptoms associated with sleep disordered breathing is challenging for healthcare professionals, since patients themselves sometimes can be unaware of having sleep disordered breathing. Daytime sleepiness is a core symptom of sleep disordered breathing and often leads to daytime napping. However, many patients with AF and/or sleep disordered breathing do not report this as a problem since daytime napping is considered as a normal habit. An important source of information during the clinical assessment is the patient’s bed-partner/spouse. The bed-partner’s sleep can be disturbed and it is common that bed-partners to patients with obstructive sleep apnoea report that they have noticed apnoeas, choking spells or disturbing snoring,10 but these signs and symptoms are less obvious for bed-partners/spouses to patients with central sleep apnoea. Thus, specific knowledge is required, as well as an awareness of relevant steps to identify patients with obstructive sleep apnoea and/or central sleep apnoea. Guidelines that describe how to identify patients with obstructive sleep apnoea have been published by the American Academy of Sleep Medicine.11 The initial step is based on a routine health examination, patient complaints (i.e. sleep history, characteristics of obstructive sleep apnoea; e.g. apneas or snoring), as well as an evaluation of occurrence of co-morbidities associated with high risk of having obstructive sleep apnoea (i.e. obesity, hypertension, diabetes). Questionnaires focusing on specific symptoms for obstructive sleep apnoea can be used to assess the presence of symptoms (e.g. Berlin Sleep Apnoea Questionnaire).12 However, an objective registration with either polygraphy (i.e. registration of nocturnal breathing patterns) or polysomnography (i.e. registration of nocturnal breathing patterns and sleep) is needed to set the medical diagnosis and evaluate possible treatment options.11 Identification of central sleep apnoea by the use of symptoms and questionnaires is less clear. However, the same objective registration methods as for obstructive sleep apnoea are used in patients with central sleep apnoea. When the sleep disordered breathing diagnosis is set, it is of utmost importance to start treatment, especially in severe cases with risk factors or daytime sleepiness. However, an elderly person with mild sleep disordered breathing without symptoms would not automatically be in need of treatment. Recommended treatment of moderate/severe obstructive sleep apnoea is in most cases CPAP,1 whereas central sleep apnoea might be treated by Auto Servo Ventilation.13 Integrated care for patients with AF appears to be efficient and effective. Recently, a randomized controlled AF study demonstrated improved guideline-adherent care and appeared to be superior in terms of reducing cardiovascular hospitalization and death.14 In this approach. nurses and cardiologists work closely together with clearly defined roles; the nurse is responsible for the education of patients and coordination of care, while the supervising cardiologist is responsible for the medical aspects. Poor guideline adherence11 can result in missed sleep disordered breathing diagnosis and, as a consequence, a risk of increased morbidity and mortality.4,15 An integrated care approach for AF could therefore be further expanded by incorporating significant aspects of sleep disordered breathing management (i.e. detection, education and treatment of sleep disordered breathing) as well as incorporating significant professionals. This can be done in several steps. First, during a clinical visit the cardiologist and/or nurse can take the medical history that also incorporates an evaluation of sleep disordered breathing symptoms and risk factors, such as age, obesity and sleep disordered breathing associated cardiovascular diseases (i.e. hypertension, heart failure and coronary artery disease). Second, before referral for further evaluation by a sleep specialist, high-risk patients should be discussed within the integrated care team. Before objective registration of sleep disordered breathing is performed, the patient should be informed about both the diagnostic procedures and different treatment options. Subsequently, patients diagnosed with sleep disordered breathing should receive in-depth education by a member of the integrated care team regarding sleep disordered breathing pathophysiology, the chosen treatment, as well as relevant lifestyle interventions (e.g. weight loss if obstructive sleep apnoea is diagnosed). Since adherence to CPAP treatment can be a significant problem,16 education and support to develop habits to improve long-term adherence can be of importance.22 Meanwhile, AF should be treated as well. Besides appropriate prescription of oral anticoagulation according to the CHA2DS2-VASc score,9 rate control would be first choice therapy. However, stabilisation of sleep disordered breathing and optimal treatment of other associated cardiovascular diseases may improve the overall control of AF.7 Since sleep disordered breathing can be considered as a hidden co-morbidity in patients with AF, an additional focus, including detection and initiation of relevant sleep disordered breathing treatment, is of utmost importance for the integrated care team. Tailored patient education about both AF and sleep disordered breathing is a key issue. Moreover, the spouses’ role in the AF care process is crucial for the detection of sleep disordered breathing, as well as for effective treatment of both conditions.