Frequency of systemic microvascular dysfunction in syndrome X and in variant angina.

In addition to coronary vascular abnormalities, patients with syndrome X and variant angina often have systemic vascular symptoms. To determine whether these patients exhibit a generalized abnormality of vasoreactivity, we used high-resolution ultrasound to compare flow responses and endothelial function in the brachial artery in 21 patients with syndrome X, 15 patients with variant angina, and 20 healthy controls. Arterial diameter was measured at rest, after reactive hyperemia (endothelium-dependent flow-mediated vasodilation), and after sublingual glyceryl trinitrate (endothelium-independent vasodilation). The magnitude of hyperemic flow response was measured after transient forearm occlusion. Flow-mediated dilation in the brachial artery did not differ among patients with syndrome X, variant angina, and controls (2.7 +/- 2.3%, 3.8 +/- 3.5%, and 4.2 +/- 3.0%). Endothelium-independent vasodilation in the brachial artery was similar in the 3 groups (16.0 +/- 7.2%, 12.7 +/- 4.6%, and 14.8 +/- 4.9%). Despite a considerable overlap, reactive hyperemia was lower in patients with syndrome X than in patients with variant angina and controls (342+/-86% vs 466+/-184% and 452+/-104%; p < 0.05). These findings indicate that a substantial proportion of patients with syndrome X have a systemic microvascular abnormality, whereas variant angina is predominantly a segmental disorder of conduit vessels.