Cardiac Disorders and Sleep Apnea: Causes and Cardiovascular Risk

Introduction

The objective of this study is to ascertain the relationship between cardiac disorders and sleep apnea. Toward this end, this work examines the current research in this area of study.

An American Heart Association/American College of Cardiology Foundation Scientific Statement reports that "sleep-related breathing disorders are highly prevalent in patients with established cardiovascular disease. Obstructive sleep apnea (OSA) affects an estimated 15 million adult Americans and is present in a large proportion of patients with hypertension and in those with other cardiovascular disorders, including coronary artery disease, stroke, and atrial fibrillation" (Somers et al., 2008, p. 1080). Central sleep apnea occurs primarily in patients with heart failure (Somers et al., 2008, paraphrased).

Halberstadt (2010) states that many deaths occurring among individuals in their 40s and older that have been attributed to heart disease or automobile accidents "may actually be related to an unseen epidemic of snoring and sleep apnea. Apnea, a potentially deadly phantom, is the frequent stoppage of breathing caused by relaxed tissues in the throat during sleep. Snoring is caused by vibrations of the relaxed throat tissues and is often the precursor or companion of sleep apnea. Although effective medical treatment for sleep apnea exists, this information has not entered routine medical practice, nor does the public recognize the dangers. Unfortunately, even when apnea is suspected, it may be difficult to obtain qualified care. As a result, 95% of the millions of people who suffer from sleep apnea have not and may never be diagnosed, let alone treated. Nevertheless, the informed person with sleep apnea can take the initiative to get appropriate diagnosis and treatment and take the steps necessary to assure recovery" (Halberstadt, 2010, p. 1). Halberstadt reports that some cardiological problems associated with sleep apnea are known, and their risk can be reduced through treating the sleep apnea.

Obstructive Sleep Apnea: Definition and Pathophysiology

Obstructive sleep apnea is characterized by "repetitive interruption of ventilation during sleep caused by collapse of the pharyngeal airway. An obstructive apnea is a 10-second pause in respiration associated with ongoing ventilatory effort. Obstructive hypopneas are decreases in, but not complete cessation of, ventilation, with an associated fall in oxygen saturation or arousal. A diagnosis of OSA syndrome is accepted when a patient has an apnea-hypopnea index (AHI; number of apneas and hypopneas per hour of sleep) of fewer than 5 and symptoms of excessive daytime sleepiness" (Somers et al., 2008, p. 1081).

While hypopneas "constitute the majority of disordered breathing events, there is some controversy regarding the optimal criteria for definition of hypopneas" (Somers et al., 2008, p. 1082). A recent analysis of data from more than 6,000 adults participating in the Sleep Heart Health Study reported that "hypopneas accompanied by oxyhemoglobin desaturation of 4% were associated with prevalent cardiovascular disease independently of confounding covariates" (Somers et al., 2008, p. 1082).

Pharyngeal collapse in patients with obstructive sleep apnea "generally occurs posterior to the tongue, uvula, and soft palate or some combination of these structures. This portion of the pharyngeal airway has relatively little bony or rigid support and is therefore largely dependent on muscle activity to maintain patency" (Somers et al., 2008, p. 1082). The primary abnormality in patients with obstructive sleep apnea is "an anatomically small pharyngeal airway resulting from obesity, bone, and soft tissue structures or, in children, tonsils and adenoids" (Somers et al., 2008, p. 1082). The result is that while the individual is awake there is increased airflow resistance and "greater intrapharyngeal negative pressure during inspiration" (Somers et al., 2008, p. 1082).

Signs, Symptoms, Risk Factors, Screening, and Treatment

Signs, symptoms, and risk factors for obstructive sleep apnea include the following:

(1) disruptive snoring; (2) witnessed apnea or gasping; (3) obesity and/or enlarged neck size; (4) hypersomolence (not common in children or in heart failure); and (5) other signs and symptoms including male gender, crowded-appearing pharyngeal airway, increased blood pressure, morning headache, sexual dysfunction, and behavioral changes (Somers et al., 2008, p. 1082).

Screening and diagnostic testing used to detect obstructive sleep apnea include the following:

(1) questionnaires; (2) Holter monitoring; (3) overnight oximetry; (4) home-based/ambulatory unattended polysomnography; and (5) in-hospital attended overnight polysomnography (Somers et al., 2008, p. 1080).

Treatment options include:

(1) positional therapy; (2) weight loss; (3) avoidance of alcohol and sedatives; (4) positive airway pressure; (5) oral appliances; and (6) surgery, including (a) uvulopalatopharyngoplasty, (b) tonsillectomy, and (c) tracheostomy (Somers et al., 2008, p. 1082).