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The terms Syndrome X or Metabolic syndrome X may also be referring to metabolic syndrome.

(Cardiac) syndrome X is angina (chest pain) with signs associated with decreased blood flow to heart tissue but with normal coronary arteries. It occurs more often in young women. Some studies have found increased risk of other vasospastic disorders in syndrome X patients, such as migraine and Raynaud's phenomenon. It is treated with calcium channel blockers, such as nifedipine, and usually carries a favorable prognosis.

This is a distinct diagnosis from Prinzmetal's angina.

Cardiac syndrome X is sometimes referred to as microvascular angina when there are findings of microvascular dysfunction.

Contents 1 Features 2 Diagnosis 3 Pathophysiology 4 Treatment 5 See also 6 References

While there is no formal definition for Syndrome X, the general consensus is that it entails all of the following:

• Angina: This usually does not cause dysfunction on echocardiogram and can last longer than that of heart disease.
• Abnormal Cardiac stress test: ST changes are typically similar to those of coronary artery disease and opposite of those with Prinzmetal's angina. Myocardial perfusion imaging can be abnormal in 30% of patients.
• Coronary angiogram: Normal

• Other causes of chest pain must be ruled out, including:
  • Prinzmetal's angina
  • Esophageal spasm

Syndrome X is a diagnosis of exclusion. Typically this will necessitate both a clinical diagnosis, appropriate stress testing, and a coronary angiogram that meet the above criteria.

In a large percentage of patients, there is a finding of systemic microvascular abnormalities, causing reduced blood flow in the microvasculature of the cardiac muscles.

While numerous physiological mechanisms have been proposed, none have been proven.

• nitrates - can reduce chest pain
• calcium channel blockers - specifically nifedipine and diltiazem can be effective.
• beta blockers - also work.
• aminophylline - may work by inhibiting adenosine receptors.
• estrogen - may work in women.

• Takotsubo cardiomyopathy

• Botker HE, Sonne HS, Sorensen KE (1996). "Frequency of systemic microvascular dysfunction in syndrome X and in variant angina". Am J Cardiol 78 (2): 182-6. PMID 8712140. 
• Cardiac Syndrome X: An Overview
• Cardiac Syndrome X
• Texas Heart Institute
• New England Journal of Medicine Editorials