TABLE 2.

Myocardial ischemia without epicardial coronary artery stenosis

Disease	Mechanism for ischemia
Syndrome X	Microvascular dysfunction
	Microvascular spasm
	Endothelial dysfunction
	Estrogen deficiency
	Increased sympathetic tone
	Diffuse epicardial and microvascular coronary constriction
	Structural abnormalities in coronary microvessels
	Inadequate vasodilatory capacity
	Nonischemic mechanisms
	Abnormal interstitial potassium release
	Adenosine release
	Early cardiomyopathy
	Increased pain perception
	Myocardial metabolic abnormality
	Insulin resistance
Diabetes mellitus	Alterations of microvessels
	Impaired microcirculatory coronary vasodilation
Left ventricular hypertrophy	Increased demand
	Inadequate vasodilatory capacity
Systemic lupus erythematosus	Thrombi (hypercoagulation, antiphospholipid antibodies)
	Vasospasm
	Arteritis
	Hypoestrogenism
	Reduced endothelial function