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Anatomic and physiologic heterogeneity in patients with syndrome X: an intravascular ultrasound study
J G Wiedermann1, A Schwartz, M Apfelbaum
1Interventional Cardiology Center, Columbia Presbyterian Medical Center, New York, New York 10032, USA.
Insights
Intravascular ultrasound reveals most patients with Syndrome X have abnormal coronary arteries, showing either plaque or thickening. These patients exhibit abnormal vasoconstriction during exercise, which is attenuated by propranolol.
Area of Science:
- Cardiology
- Vascular Biology
- Diagnostic Imaging
Background:
- Syndrome X (chest pain, abnormal exercise tests, normal angiography) pathophysiology is unclear.
- Coronary angiography has limitations in defining coronary artery disease.
- Intravascular ultrasound (IVUS) offers detailed coronary morphology assessment.
Purpose of the Study:
- To assess coronary morphology and vasoreactivity in Syndrome X using IVUS.
- To evaluate exercise-induced vasomotion before and after beta-blockade.
- To correlate coronary artery morphology with vasomotor response.
Main Methods:
- Thirty patients with Syndrome X underwent IVUS of epicardial vessels.
- Coronary lumen area was measured at rest and during supine arm exercise.
- The protocol was repeated after intravenous propranolol administration.
Main Results:
- IVUS identified three groups: normal arteries (n=12), atheromatous plaque (n=10), and intimal thickening (n=8).
- Normal arteries showed vasodilation (+16.9%) with exercise; abnormal arteries showed vasoconstriction (-17.4% to -17.6%).
- Propranolol attenuated exercise-induced vasoreactivity in all groups.
Conclusions:
- Most Syndrome X patients have abnormal coronary arteries detected by IVUS.
- Abnormal coronary arteries (plaque/thickening) correlate with abnormal vasoconstriction during exercise.
- Propranolol affects vasoreactivity, suggesting potential therapeutic differences.
Objectives:
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.