[X syndrome: review of concepts]

Patients with syndrome X or microvascular angina present complains of effort angina associated with normal--appearing coronary arteries. Ischemia seems to be caused by myocardial perfusion abnormalities, related to microcirculatory disfunction, characterized by excessive vasoconstriction and/or inadequate vasodilation response. The intimal cause of this microcirculatory disfunction, located in the small pre-arteriolares arteries with 100-200 microns caliber, is still unknown. It seems that these patients present a generalized abnormality of the systemic smooth muscle, affecting territories other than the vascular. The diagnosis should be suspected whenever a patient presents effort angina, angiographically normal arteries and evidence of ischemia to exercise. As this syndrome is better understood some subsets of patients with different clinical characteristics and prognosis, are being identified. The calcium channel blockers seem to be the drug more effective in the control of ischemia and symptoms. The prognosis is, in general, better than in patients with coronary angiographic lesions.