Microvascular angina

Did You Know?

• Patients often experience myocardial ischemia symptoms such as heaviness, tightness, pressure, or squeezing in the chest, along with sweating, nausea, shortness of breath, and fatigue.
• Women are more prone to develop microvascular angina than men, possibly due to hormonal factors and the constant changing of estrogen levels.

Causes

No specific cause is known; rather, multiple risk factors act together. Impaired blood flow due to microvascular disease and an enhanced perception of pain are believed to contribute. The microvascular dysfunctions involve abnormalities in the heart's very small blood vessels, whose narrowing can deprive areas of cardiac muscle of oxygen and cause chest pain. Studies indicate that affected individuals often feel more intense chest pain than those without the condition. Risk factors include abdominal obesity, atherogenic dyslipidemia, elevated blood pressure, insulin resistance or glucose intolerance, and a prothrombotic or proinflammatory state. Older people are at higher risk, and there is evidence of genetic predispositions. Women are more prone than men, as are those with a family history of heart disease.

Types of microvascular dysfunction

Structural coronary microvascular dysfunction is characterized by an inability to dilate, with high vascular tone at rest and during stress, normal resting coronary blood flow (CBF), lower stress CBF, low coronary flow reserve (CFR), and elevated hyperemic index of microcirculatory resistance (hMR). It involves luminal obstruction, vascular-wall infiltration, vascular remodeling, perivascular fibrosis, and capillary rarefaction. Functional coronary microvascular dysfunction presents with exhausted dilatory capacity, low vascular tone at rest and stress, elevated rest CBF, normal stress CBF, lower CFR, normal hMR, and higher nitric oxide synthase activity. It features endothelial, smooth-muscle, and autonomic dysfunction.

Diagnosis

Microvascular angina is a diagnosis of exclusion, typically requiring clinical evaluation, stress testing, and a coronary angiogram that shows normal arteries. Cardiac MRI may be used, though studies to validate this are ongoing. An angiogram with acetylcholine can reveal microvascular dysfunction affecting both microvessels and larger arteries, distinguishing it from coronary artery spasms (Prinzmetal's angina), though some individuals have both. Sedentary, overweight individuals with a family history of type 2 diabetes should be regularly tested for glucose, lipid, or blood pressure abnormalities. An exercise stress test can show inadequate blood flow during exertion. Angiograms provide detailed heart images but cannot detect small artery abnormalities, so additional tests may rule out conditions like Prinzmetal's angina. Chest pain from microvascular angina is often unpredictable, occurring at rest or during exercise, and tends to be more intense and longer-lasting than pain from other causes. Gastric conditions are a common differential diagnosis. Unlike stable angina, nitroglycerin is ineffective in most patients with microvascular angina.

Treatment

Calcium channel blockers (nifedipine, diltiazem) and beta-blockers can be effective, though beta-blockers may worsen coronary spasms. Aminophylline may work by inhibiting adenosine receptors. Estrogen can be effective in women. L-arginine promotes vasodilation by increasing nitric oxide release. Ranolazine has been shown to improve angina and myocardial ischemia. Statins, aspirin, clopidogrel, ACE inhibitors, and ARBs are also used. Lifestyle changes include a diet low in saturated fats, regular physical activity (after medical clearance), and smoking cessation. Pain management may involve cognitive behavioral therapy, mindfulness meditation, yoga, and Tai Chi. Microvascular angina is a chronic condition that raises the risk of heart attack, heart failure, and frequent hospital admissions. Nitrates are often the first step but are ineffective in up to half of patients. There is no known cure.