What is microvascular angina (cardiac syndrome X)?

From the Guidelines

Microvascular angina, also known as cardiac syndrome X or coronary microvascular dysfunction, is a condition characterized by chest pain caused by abnormalities in the small blood vessels of the heart, rather than blockages in the major coronary arteries. This condition occurs when the tiny arteries in the heart don't dilate properly, limiting blood flow to the heart muscle despite the main coronary arteries appearing normal on angiography 1. Patients typically experience chest pain similar to classic angina, often triggered by physical exertion or emotional stress.

Key Characteristics

• The condition is more common in women, particularly those who are post-menopausal 1
• It can significantly impact quality of life and may indicate an increased risk for other cardiovascular events 1
• Diagnosis is suggested by the triad of anginal-type chest discomfort, objective evidence of ischemia, and absence of obstructive CAD 1

Treatment

• Treatment usually involves medications such as beta-blockers, calcium channel blockers, nitrates, and statins to improve blood flow and reduce symptoms 1
• ACE inhibitors and ranolazine may also be beneficial 1
• Lifestyle modifications including regular exercise, stress management, and a heart-healthy diet are important components of management 1

Recent Guidelines

• The 2023 AHA/ACC/ACCP/ASPC/NLA/PCNA guideline for the management of patients with chronic coronary disease recommends baseline therapy with aspirin, statin, and ACEi, as well as sublingual nitroglycerin as needed, and lifestyle changes for patients with microvascular angina 1
• The 2019 ESC guidelines for the diagnosis and management of chronic coronary syndromes recommend treatment of microvascular angina based on the dominant mechanism of microcirculatory dysfunction, including beta-blockers, ACE inhibitors, and statins, along with lifestyle changes and weight loss 1

From the Research

Definition and Characteristics of Microvascular Angina

• Microvascular angina (MVA), also known as cardiac syndrome X, is defined as angina pectoris caused by abnormalities of small coronary arteries 2, 3, 4, 5, 6.
• It is characterized by angina attacks mainly caused by effort, evidence of myocardial ischemia on non-invasive stress tests, but normal coronary arteries at angiography 2, 4, 6.
• Patients with MVA often present with persistent and/or worsening of angina symptoms, despite excellent long-term prognoses 2, 3.

Pathophysiology and Etiology

• The cause of MVA seems almost certain to be organic and functional abnormalities of the small arteries of the heart 3.
• Patients with MVA are likely to suffer from endothelial dysfunction and other microvascular abnormalities of both the coronary and peripheral arteries 3, 6.
• Altered somatic and visceral pain perception and autonomic imbalance, in addition to myocardial ischemia, has been observed in subjects with MVA 6.
• Other theories suggest that MVA may be a result of a chronic inflammatory state in the body that can negatively influence the endothelium or a local imbalance of factors regulating its function 6.

Treatment and Management

• Treatment of MVA is initially based on standard anti-ischemic drugs (beta-blockers, calcium antagonists, and nitrates), but control of symptoms is often insufficient 2.
• Several additional drugs, with different potential anti-ischemic effects, have been proposed, including ranolazine, ivabradine, angiotensin-converting enzyme (ACE) inhibitors, xanthine derivatives, nicorandil, statins, alpha-blockers and, in perimenopausal women, estrogens 2, 4, 5.
• Beta-blockers and calcium channel blockers have the strongest evidence of improving the symptoms 5.
• The use of angiotensin-converting enzyme inhibitors or angiotensin receptor blockers, statins, estrogen, and novel antianginal drugs has had promising outcomes 5.
• Investigations are still ongoing for vitamin D, omega-3, incretins, and n-acetyl cysteine, which have resulted in beneficial initial outcomes 5.