Q. ST-segment depression after hyperventilation?
Patients with abnormal autonomic drive have demonstrated ST-segment depression after hyperventilation as well as after exercise. Patients who display ST-segment depression at rest or an increased ST-segment depression after hyperventilation, in whom the depression tends to return to normal with exercise usually do not have epicardial CAD. Changes associated with hyperventilation are associated with normal coronary arteries. Propranolol and other beta-blockers have been shown to back the ST changes associated with hyperventilation, suggesting an autonomic etiology. The common findings that body position may produce similar changes tends to support this concept. These types of changes are common in patients with mitral prolapse.