Obstructive sleep apnea occurs when the upper airway is obstructed during sleep, resulting in repeated pauses in breathing (apnea) and recurrent oxygen desaturations.
During the later stages of sleep, the muscles relax and can obstruct the airway, especially if a significant amount of adipose tissue is also present; thus, obesity is a major risk factor for OSA. This results in repeated awakening, despite the patient being unaware, and an overall increase in the baseline activity of the sympathetic nervous system, which contributes to the adverse cardiovascular effects of OSA.
The major symptoms of obstructive sleep apnea include fatigue and headaches. OSA is a common cause of secondary hypertension.
Below are five cardiovascular complications of obstructive sleep apnea.
- Hypertension: OSA is well known to cause hypertension. In severe cases, the hypertension can be refractory to medical management unless the sleep apnea is controlled. The mechanism is theorized to be related to enhanced sympathetic tone. Some degree of hypertension in patients with sleep apnea is likely related to obesity.
- Right heart failure: OSA causes pulmonary hypertension from chronic hypoxemia. This can lead to right heart failure.
- Ischemic heart disease: OSA is known to cause coronary artery disease and increase the risk for acute coronary syndromes, likely due to enhanced sympathetic tone and hypertension.
- Arrhythmia: Atrial fibrillation and atrial flutter are very strongly associated with OSA. Some studies estimate 82% of patients with atrial fibrillation/flutter have sleep apnea; this is likely an overestimate. Bradycardia and asystole are common during sleeping hours in patients with OSA, but the clinical importance of this is not clear. Bradycardia can occur during waking hours, as well, but it is less common. One study reported that almost 60% of patients who required a permanent pacemaker (for sick sinus syndrome or AV block) had obstructive sleep apnea. Premature ventricular and atrial contractions are markedly more common in patients with OSA. These can be symptomatic.
- Left heart failure: Some studies suggest that OSA, when severe, may be the cause of LV systolic dysfunction and left heart failure in some patients.