Patients who have obstructive sleep apnea have a higher risk for ischemic heart diseases than the general population. The repetitive hypoxic events and sympathetic stimulation in these patients place demands on the heart that may expose patients with limited cardiac reserve to the danger of nocturnal ischemic events. Peled and associates studied nocturnal ischemic events in patients with obstructive sleep apnea and the impact of continuous positive airway pressure (CPAP) on these events.

Fifty-one patients who had an established diagnosis of obstructive sleep apnea and ischemic heart disease were enrolled in the study. Patients underwent whole-night polysomnography, including continuous Holter monitoring and ambulatory blood pressure readings. Some of the patients were treated with CPAP during the monitoring. A control group of patients without ischemic heart disease were monitored for comparison.

Nocturnal ST segment depression or ischemic events occurred in 29 percent of the patients with obstructive sleep apnea and ischemic heart disease, with some having early morning ischemia. This depression mainly occurred during the rebreathing phase of sleep apnea and was characterized by an increase in the heart rate and increased nocturnal double product values. The use of CPAP had a positive impact on both variables. In the control group with no history of ischemic heart disease, no ischemic events were recorded.

The authors conclude that obstructive sleep apnea is associated with ischemic events in patients with a history of ischemic heart disease. Treating these patients with CPAP can significantly reduce these events. They also note that a history of ischemic heart disease is the main risk factor for ischemic events in patients with obstructive sleep apnea.