Intravascular ultrasound detection of atherosclerosis at the site of focal vasospasm in angiographically normal or minimally narrowed coronary segments.

OBJECTIVES

The purpose of this study was to use intravascular ultrasound imaging to examine the presence of occult atherosclerosis at the site of focal vasospasm in angiographically normal or minimally narrowed segments, testing the role of atherosclerosis in the development of vasospasm.

BACKGROUND

Previous clinical and experimental studies have suggested that early atherosclerosis is present at the site of focal vasospasm. However, no clinical data exist demonstrating occult disease at the site of vasospasm at angiographically insignificant stenoses.

METHODS

Twenty-two patients with chest pain at rest or during exertion, or both, were studied. Vasospasm was provoked by intracoronary administration of ergonovine maleate (0.01 to 0.04 mg). After relief of vasospasm by nitroglycerin administration, intravascular ultrasound imaging was performed with a 32- or 64-element, 20-MHz, synthetic aperture array ultrasound device.

RESULTS

Focal vasospasm (arterial diameter reduction > or = 90%) with ST-T segment elevation was provoked in 15 patients: in the left anterior descending coronary artery in 8 patients and in the right coronary artery in 7. The remaining seven patients (control group) showed diffuse narrowing, averaging 22 +/- 12% (mean +/- SD) in diameter from the baseline angiograms after ergonovine administration. Atherosclerosis, defined as a significantly thickened intimal leading edge (0.42 +/- 0.07 mm) associated with an increased sonolucent zone (0.57 +/- 0.30 mm), was detected by ultrasound at all 15 sites with focal vasospasm, although these sites were normal or minimally narrowed by angiography. In contrast, seven segments from the control group exhibited a thin intimal leading edge (0.14 +/- 0.04 mm, p < 0.01) and sonolucent zone (0.10 +/- 0.07 mm, p < 0.01), indicating the absence of localized atherosclerotic lesions.

CONCLUSIONS

These results indicate that atherosclerosis is present at the site of focal vasospasm, even in the absence of angiographically significant coronary disease. We suggest that the existence of such atherosclerotic lesions is related to the occurrence of focal vasospasm in the clinical settings.