Syndrome X
{{Chronic stable angina]]
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]
The terms Syndrome X or Metabolic syndrome X may also be referring to metabolic syndrome.
Synonyms and key words: Microvascular angina
Overview
(Cardiac) syndrome X is angina (chest pain) associated with objective evidence of myocardial ischemia in the setting of normal epicardial coronary arteries. It is thought to involve the coronary microvasculature rather than the large epicardial arteries.
Pathophysiology
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.
Epidemiology and Demographics
Syndrome X 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.
Natural history, complications, and prognosis
Syndrome X does not appear to be associated with an excess of major coronary events.
Risk Factors
Female gender and hypertrophy of the myocardium are associated with an excess risk of Syndrome X.
Other Conditions to Distinguish Syndrome X From
Syndrome X is a distinct diagnosis from Prinzmetal's angina which involves spasm of the main epicardial coronary arteries. Syndrome X involves spasm of the downstream microvasculature. Syndrome X must also be distinguished from esophageal spasm.
Diagnosis
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 criteria below:
- To establish the diagnosis, patients must have evidence of myocardial ischemia by exercise ECG, stress scintigraphy, or stress echocardiography in conjunction with anginal chest discomfort.
- Some of these patients have documented reductions in coronary vasodilator reserve presumably due to abnormalities in the coronary microcirculation and can be shown to have true ischemia because their myocardium produces lactate rather than removing it during stress. 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
Treatment
The mainstay of treatment in patients with Syndrome X are calcium channel blockers, such as nifedipine and diltiazem. Other therapies include:
- Nitrates
- Beta blockers
- Aminophylline - may be effective via inhibition of adenosine receptors.
- Estrogen - may be effective in women.
ESC Guidelines for investigation in patients with Syndrome X (DO NOT EDIT)[1]
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Class I1. Resting echocardiogram in patients with angina and normal or non-obstructed coronary arteries to assess for presence of ventricular hypertrophy and/or diastolic dysfunction. (Level of Evidence: C) Class IIb1. Intracoronary acetylcholine during coronary arteriography, if the arteriogram is visually normal, to assess endothelium-dependent coronary flow reserve, and exclude vasospasm. (Level of Evidence: C) 2. Intracoronary ultrasound, coronary flow reserve, or FFR measurement to exclude missed obstructive lesions, if angiographic appearances are suggestive of a nonobstructive lesion rather than completely normal, and stress imaging techniques identify an extensive area of ischaemia. (Level of Evidence: C) |
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ESC Guidelines for pharmacological therapy to improve symptoms in patients with Syndrome X (DO NOT EDIT)[1]
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Class I1. Therapy with nitrates, beta blockers, and calcium channel blockers alone or in combination. (Level of Evidence: B) 2. Statin therapy in patients with hyperlipidaemia. (Level of Evidence: B) 3. ACE inhibitors in patients with hypertension. (Level of Evidence: C) Class IIa1. Trial of therapy with other anti-anginals including nicorandil and metabolic agents. (Level of Evidence: C) Class IIb1. Aminophylline for continued pain, despite Class I measures. (Level of Evidence: C) 2. Imipramine for continued pain, despite Class I measures. (Level of Evidence: C) |
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References
- ↑ 1.0 1.1 Fox K, Garcia MA, Ardissino D, Buszman P, Camici PG, Crea F; et al. (2006). "Guidelines on the management of stable angina pectoris: executive summary: The Task Force on the Management of Stable Angina Pectoris of the European Society of Cardiology". Eur Heart J. 27 (11): 1341–81. doi:10.1093/eurheartj/ehl001. PMID 16735367.