Waking and rising at night as a trigger of myocardial ischemia.

A diurnal pattern of changes in transient myocardial ischemia has been well documented in patients with coronary artery disease (CAD) with an increase in the early morning hours. To further investigate potential triggers of ischemia, certain defined and distinct episodes of waking and rising during the nighttime were examined. Of 113 patients who underwent ambulatory monitoring of the electrocardiogram, 466 episodes of ischemia lasting 3,926 minutes were detected in 67 of the patients. In 30 patients who had ischemia at night, 21 reported 36 occasions of waking and rising, and 67% of these events were associated with ST-segment depression. Frequency and duration of ischemia were similar in the nocturnal episodes versus the early morning episodes of ischemia as were the increases in heart rate at 30, 10, 5 and 1 minute before the onset. Even before waking, there was an increase in heart rate beginning approximately 30 minutes before the onset of ischemia. This increase became significant 5 minutes before onset both in the early morning and on rising at night. Patients with nocturnal ischemia had significantly worse clinical signs of CAD. This study shows that rising at night is often associated with episodes of myocardial ischemia and, like the morning events on rising, is likely an important trigger of ischemia in patients with CAD.