Alternate Names: Accelerating angina; New-onset angina; Angina - unstable; Progressive angina

Causes and Risks:

Unstable angina occurs in approximately 6 out of 10,000 people. Coronary artery disease secondary to atherosclerosis is by far the most common cause of unstable angina. A coronary artery spasm can cause angina in fewer than 10% of cases.

Initially, narrowing (plaques) of the coronary arteries occurs may be severe enough to cause stable angina with exertion or stress. This narrowing, however, may not cause any symptoms at all. For reasons not well understood, the plaques reach a point at which they rupture. Under these circumstances, a plug formed by platelets and blood clots may form causing an already narrowed blood vessel to become "high-grade." This inherently unstable situation may progress to complete occlusion and infarction (cell death) or the lesion may heal. When this plug completely occludes a coronary artery, a heart attack occurs.

Once this type of lesion exists, onset of chest pain is "unstable." Unlike stable angina, in which chest pain can be induced by exercise or stress, chest pain secondary to unstable angina may occur at rest and without any precipitating factors at all. Pain may increase in the severity, frequency, or duration at low levels of activity or for no identifiable reason. Diabetes mellitus, hypertension, myxedema, peripheral vascular disease, heart valve disease, cardiomyopathy, and atherosclerosis may also produce this type of angina.

Risk factors for unstable angina are similar to those for stable angina, and include:

• male gender
• cigarette smoking
• high cholesterol levels (in particular, high LDL cholesterol and low HDL cholesterol)
• high blood pressure
• diabetes
• family history of coronary heart disease before age 55
• sedentary lifestyle
• being more than 30% over ideal body weight

Occasionally, sudden overwhelming stress can precipitate an episode of angina.

Prevention:

The best prevention of unstable as well as stable angina is to modify those risk factors that can be changed.

• stop smoking
• lose weight if overweight
• control blood pressure, diabetes, and cholesterol

In fact, some studies have shown that modifying risk factors can prevent the progression of arterial blockages and can lead to decrease in the severity of blockages.

Aspirin, antianginal medications such as nitrates (nitroglycerin), beta-blockers, calcium channel blockers, or others may be prescribed to prevent the occurrence of angina and lessen its severity.

Symptoms:

Typical anginal pain usually originates in the chest and may radiate to shoulder, arm, jaw, neck, back or other areas. The pain is often described as tightness, squeezing, crushing, burning, choking, or aching. Unstable angina is differentiated from stable angina in that the pain may:

• occur at rest
• be new onset or last longer than previous anginal attacks
• be less responsive to medication

In other words, if a pattern of stable angina has been present previously, the development of unstable angina may be signified by a change in the pattern, frequency, or severity.

Signs and Tests:

• Physical examination may reveal a change in blood pressure. Transient heart murmur or arrhythmias (irregular heart beats) may occur as well.
• ECG changes that occur at rest, during pain, are often diagnostic.
• Heart scans or coronary angiographies of the heart are often performed.
• Echocardiography may reveal changes in the heart caused by decreased coronary blood flow.
• Blood tests such as CPK, CPK-MB, Troponin I, and Troponin T are used to diagnose unstable angina and can predict likelihood of progression to heart attack.

Treatment:

Complications of unstable angina include sustaining an acute MI without warning, or sudden death from lethal arrhythmias.

In this way, unstable angina is a severe condition. An individual experiencing unstable angina usually requires hospitalization. The goals of treatment include reduction of symptoms and prevention of complications.

Rest if chest pain occurs.

Aspirin, heparin, and nitroglycerin (often by paste or intravenously) are given during an attack. Other medications include beta-blockers, calcium channel blockers, antianxiety medications, and medications to control blood pressure and abnormal heart rhythms.

Surgery may be recommended. CABG (coronary artery bypass grafting) or PTCA (balloon angioplasty) may be necessary.

New anti-platelet medications are being used in unstable angina. They are often used in combination with PTCA.

Prognosis:

The outcome varies depending on many factors. The most important factor is the severity of the underlying coronary artery disease. Other factors include the severity of the episode, past history of heart attack, and the number of medications a patient had already been taking when the episode began.