Anatomic and physiologic heterogeneity in patients with syndrome X: An intravascular ultrasound study

Objectives.We used intravascular ultrasound imaging of the epicardial vessels to assess coronary morphology, vasomotor response to exercise and exercise-vasomotion after betaadrenoceptor blockade in patients with syndrome X.Background.Syndrome X is defined as chest pain, abnormal exercise test results and normal coronary angiographic findings. Because of the limitations of coronary angiography, intravascular ultrasound was used to define coronary pathophysiology.Methods.Thirty patients with syndrome X were studied with intravascular ultrasound imaging (30 MHz, 4.3F catheter) of all three major epicardial vessels. Supine arm exercise was performed during coronary imaging. Lumen area was assessed at rest and during peak exercise. The exercise-imaging protocol was repeated after loading with 0.1 mg/kg body weight of intravenous propranolol.Results.Three morphologic groups were identified using intravascular ultrasound: normal coronary arteries (no plaque, intimal thickness