Microvascular angina in patients with syndrome X.

Syndrome X (SX) is usually diagnosed in the presence of angina and normal coronary arteriograms. It is an heterogeneous syndrome which encompasses different pathogenic mechanisms. Whether myocardial ischaemia is responsible for the condition remains controversial. The term "microvascular angina" has been used to define the syndrome of chest pain and normal coronary arteries with heightened sensitivity of the coronary microcirculation to vasoconstrictor stimuli. It has been suggested that the abnormal vasodilator response of the coronary circulation in patients with SX is due to impaired endothelial function. Plasma levels of endothelin in patients with chest pain and normal coronary arteries were found to be significantly raised compared to normal controls. Endothelial dysfunction in SX is likely to be multifactorial and many cardiac risk factors, such as hypertension, hypercholesterolemia, oestrogen deficiency and smoking, can contribute to its development. As the majority of SX patients are women and most are post-menopausal, oestrogen deficiency has been proposed as a pathogenic factor. A large proportion of patients satisfying the stated criteria for SX have one or more coronary risk factors. Additional factors, such as abnormal pain perception, may contribute to the evolution of chest pain in patients with normal coronaries and endothelial dysfunction. Combined alteration of pain perception and microvascular dysfunction are likely to explain a proportion of all cases of SX. The treatment of this syndrome represents a major challenge for the cardiologist. Beta-blockers and calcium channel blockers are effective in controlling chest pain in SX patients. A very important therapeutic intervention in microvascular angina is the control of risk factors that can lead to endothelial dysfunction. Different approaches, including spinal cord stimulation and psychological treatment, have been proposed especially for those patients in whom a cardiac origin of pain is unlikely.