Author + information
- Received September 15, 1994
- Revision received December 6, 1994
- Accepted December 15, 1994
- Published online May 1, 1995.
- Joseph G. Wiedermann, MD,
- Allan Schwartz, MD, FACC and
- Mark Apfelbaum, MD, FACC*
- ↵*Address for correspondence: Dr. Mark Apfelbaum, Columbia-Presbyterian Medical Center, Interventional Cardiology Center M2HS, 622 West 168th Street, New York, New York 10032.
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 <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.
This study was presented in part at the 66th Annual Scientific Sessions of the American Heart Association, Atlanta, Georgia, November 1993 and was supported in part by a grant from the Milstein Family Foundation, New York, New York.
- Received September 15, 1994.
- Revision received December 6, 1994.
- Accepted December 15, 1994.
- American College of Cardiology