The five cardiovascular complications of obstructive sleep apnea (OSA) are:

1. 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 sleep apnea patients is likely related to obesity.

2. Right heart failure: OSA causes pulmonary hypertension from chronic hypoxemia. This can lead to right heart failure.

3. Ischemic heart disease: OSA is known to cause coronary artery disease and increase the risk of acute coronary syndromes, likely due to enhanced sympathetic tone and hypertension.

4. 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 (likely an overestimate).
- Bradycardia and asystole are common during sleeping hours in patients with obstructive sleep apnea. However the clinical importance of this is not clear. Bradycardia can occur during waking hours, but less commonly. One study reported that almost 60% of patients that needed 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.

5. Left heart failure: Some studies suggest that OSA may be the cause of LV systolic dysfunction and left heart failure in some patients when severe.