Cardiac Syndrome X (Microvascular Dysfunction)

Definition and Pathophysiological Mechanisms

Cardiac Syndrome X, also known as microvascular angina, is a condition characterized by anginal symptoms, evidence of myocardial ischemia in diagnostic tests, but with **angiographically normal epicardial coronary arteries**.

The pathogenesis is linked to an alteration in coronary microcirculation function, leading to reduced coronary flow reserve. The main pathophysiological mechanisms involved include:

Endothelial dysfunction: Reduced nitric oxide production and impaired vasodilation.
Increased vascular tone: Hyperreactivity of the autonomic nervous system with inappropriate vasoconstriction.
Chronic inflammation: A pro-inflammatory state that alters vascular response.
Microcirculatory regulation abnormalities: Reduced coronary perfusion despite normal angiography.

Epidemiology and Risk Factors

Cardiac Syndrome X primarily affects postmenopausal women and represents an underdiagnosed cause of angina.
It is more common in smokers and individuals with other traditional cardiovascular risk factors (hypertension, dyslipidemia, diabetes mellitus, metabolic syndrome).

Clinical Presentation and Diagnosis

Patients with Cardiac Syndrome X experience **typical chest pain**, similar to angina caused by coronary stenosis, but with specific characteristics:

Chronic angina, often persistent and not always related to exertion.
Poor response to nitrates, unlike angina caused by coronary obstruction.
Evidence of myocardial ischemia in provocative tests, but normal coronary arteries on angiography.

The most useful diagnostic tests include:

Baseline ECG and stress test: Possible nonspecific ST-segment changes and T-wave inversion.
Myocardial scintigraphy and cardiac MRI: Show reduced microvascular perfusion.
Stress echocardiography: Segmental wall motion abnormalities in the absence of coronary obstruction.
Coronary angiography with coronary reactivity testing: Confirms the absence of significant epicardial coronary stenosis.

Treatment of Cardiac Syndrome X

The treatment aims to improve myocardial perfusion and reduce anginal symptoms.

Lifestyle Modifications: Adopting a healthy lifestyle is essential. A Mediterranean diet, regular physical activity, and smoking cessation improve endothelial function and reduce inflammation.

Pharmacological Therapy:

Beta-blockers: Improve exercise tolerance and reduce myocardial oxygen consumption.
Calcium channel blockers: Vasodilation of coronary arterioles.
ACE inhibitors and ARBs: Improve endothelial function.
Statins: Anti-inflammatory effects and endothelial dysfunction stabilization.
Ranolazine and Trimetazidine: Improve myocardial metabolism and reduce symptoms.

Prognosis and Complications

Although Cardiac Syndrome X is not associated with an increased risk of myocardial infarction, it can significantly reduce quality of life. Optimal therapeutic management is essential for controlling symptoms and preventing recurrent anginal episodes.

References

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Fox K, et al. Stable angina and microvascular disease. BMJ. 2019;364:k5404.