title: Anatomic and physiologic heterogeneity in patients with syndrome X: an intravascular ultrasound study.
abstract: OBJECTIVE
  We used intravascular ultrasound imaging of the epicardial vessels to assess coronary morphology, vasomotor response to exercise and exercise-vasomotion after beta-adrenoceptor 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 < 0.25 mm, n = 12), atheromatous disease (mean [+/- SD] area stenosis 37.9 +/- 7.2%, n = 10) and marked intimal thickening (0.73 +/- 0.11 mm, n = 8). Patients with normal coronary arteries displayed a vasodilatory response to exercise (+16.9% area increase); patients with abnormal coronary arteries displayed a vasoconstrictive response to exercise (-17.4% in the group with plaque; -17.6% in the group with intimal thickening). Propranolol loading attenuated the vasodilatory response in the group with normal coronary arteries (+6.4% area increase) and attenuated the vasoconstrictive response in the two groups with abnormal coronary arteries (-8.0% in the group with plaque; -8.8% in the group with intimal thickening).
  
  
  CONCLUSIONS
  Most patients with syndrome X have abnormal coronary arteries by intravascular ultrasound. Intravascular ultrasound identifies three distinct morphologic groups: normal coronary arteries, atheromatous plaque and intimal thickening. Exercise-vasomotion is normal in patients with syndrome X who have normal coronary arteries by ultrasound; patients with abnormal arteries (plaque or intimal thickening) have an abnormal (constrictive) response to exercise. Propranolol loading attenuates vasoreactivity in all subgroups, suggesting divergent therapeutic utility.
authors.affiliation: Interventional Cardiology Center, Columbia Presbyterian Medical Center, New York, New York 10032, USA.
authors.forename: J G
authors.initials: JG
authors.lastname: Wiedermann
authors.forename: A
authors.initials: A
authors.lastname: Schwartz
authors.forename: M
authors.initials: M
authors.lastname: Apfelbaum
mesh_terms: D000704:Analysis of Variance; D017023:Coronary Angiography; D003331:Coronary Vessels / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D005080:Exercise Test; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D017566:Microvascular Angina / Q000000981:diagnostic imaging* / Q000473:pathology / Q000503:physiopathology; D008875:Middle Aged; D015588:Observer Variation; D011433:Propranolol / Q000494:pharmacology; D012307:Risk Factors; D016683:Supine Position; D014463:Ultrasonography; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D014664:Vasodilation / Q000502:physiology
chemical_list: D011433:Propranolol