Unstable angina can present with symptoms that mirror those that occur in a patient with myocardial ischemia or myocardial infarction and include the following:

• Chest pain
• Shortness of breath
• Diaphoresis
• Dizziness
• Lightheadedness
• Fatigue
• Nausea
• Vomiting
• Pain or pressure like or burning sensation in the neck, jaw, neck, shoulder or arm
• Abdominal pain

The symptoms often occur at rest and are aggravated by exercise or any type of physical activity. Often the symptoms fail to respond to nitroglycerin. In many cases, the patient may complain of symptoms at rest.

Physical exam may reveal:

• Diaphoresis which is most pronounced when having chest pain.
• Elevated jugular venous pressure in people with heart failure or myocardial dysfunction.
• Hypotension can be persistent and require vasopressor therapy.
• Tachycardia or bradycardia

Auscultation may reveal:

• New heart murmur may be heard.
• Presence of S3 or S4.
• Rales or crackles.

Over the years several classifications have been developed to grade unstable angina. These include the Braunwald Classification, Canadian Cardiovascular Society Grading System, Acute Coronary Syndrome Risk Assessment and Thrombolysis in Myocardial Infarction Risk Score. In general, all these scoring system grade the angina based on severity of chest pain, the precipitating factor and response to therapy.

The most important thing to determine in a patient with unstable angina is the degree of coronary artery disease and how serious it is. Routine workup of a patient with unstable angina requires the following:

• Complete blood count
• Lipid profile
• Renal function
• Serial cardiac enzymes such as troponin, creatine kinase, C-reactive protein (CRP) and brain (B-type) natriuretic peptide (BNP) [5]
• Serum electrolytes

ECG is the first line assessment in patients with unstable angina which should be obtained soon after admission to the ER. Any patient with chest pain with ECG evidence of ST-segment elevation or development of a new left bundle branch block needs an urgent cardiology consult. These patients often benefit from immediate revascularization treatment. Subsequent ECGs depend on the symptoms. If there is any clinical or laboratory evidence of worsening of the patient, serial ECGs should be ordered at least every 30 minutes to follow progression of ST-segment changes. It should be noted that primary T-wave changes alone are not sensitive indicators for ischemia.

Imaging

• Chest X-ray to look for signs of heart failure, mediastinal widening, pneumothorax or pleural effusion.
• Echocardiography to assess valvular function and pericardial fluid collection.
• CT angiography to assess coronary artery disease
• Exercise testing when the patient is stable.
• Myocardial perfusion imaging is useful test and highly sensitive for detecting acute myocardial infarction.
• Cardiac catheterization is the test to determine presence or absence of coronary disease. It may also be used as a provocative test to check for vasospasm. In patients with critical coronary artery stenosis, angioplasty and stenting may be done.

The treatment of unstable angina requires admission with bed rest [6] [7]. All patients must be continuously monitored and have at least two intravenous lines. Oxygen is often provided if the patient saturation is below 94%. It is important to realize that unstable angina is a very unpredictable disorder and is life threatening. These patients are best monitored in an ICU setting or a cardiology floor where continuous monitoring is available.

The treatment of unstable angina is guided at the cause of ischemia and reinstitution of blood flow to the heart [8]. Many guidelines have been published about management of unstable angina patients. While some patients will benefit from medical therapy, others may require intensive care admission or emergency revascularization. Patients who are symptomatic despite therapy or are hemodynamically unstable should have emergency revascularization. Patients who respond to treatment still should observed closely with continuous telemetry. The classes of medications that are used to treat unstable angina include:

• Anti-platelet agents like aspirin, heparin, thienopyridines (clopidogrel and prasugrel) and glycoproteins GP llb/llla antagonists. It is important to ensure that the patient has no active bleeding and is not a risk for future episodes of hemorrhage.
• Beta adrenergic blockers can be used but should be avoided in patients with hypotension.
• Angiotensin converting enzyme inhibitors can be used to lower afterload.
• Nitrates are often given to treat chest pain and lower blood pressure.
• Statins are used once the patient has stabilized.

Aspirin is started on all patients within 30 mins of admission to those who are not at risk for bleeding or have any allergies to the agent. Beta-blockers do relieve ischemic symptoms but are contraindicated in patients with shock or bradycardia. Oral beta blockers are preferred to the IV drugs. Newer anti-platelet agents that can be used to treat unstable angina patients include use of prasugrel, ticagrelor, abciximab, eptifibatide or tirofiban. These agents can decrease symptoms but often do not affect the long-term risk of major adverse events.

During the initial period of admission, the patient should be kept nil per os just in case an invasive procedure or other study is anticipated. For the stable patient, a low sodium and a low cholesterol diet is recommended.

For patients who remain unstable despite maximal therapy, cardiac catheterization is recommended. These include patients with:

• Cardiogenic shock
• Echocardiogram showing depressed left ventricular ejection fraction
• Development of new or worsening of mitral regurgitation
• Development of a ventricular septal defect
• Presence of unstable tachyarrhythmia

So far, there is debate on benefits of non-invasive therapy versus invasive therapy. Not all patients with unstable angina have triple vessel coronary disease and in some cases, there is only minimal disease. In general, coronary artery bypass is recommended for patients with:

• Left main coronary stenoses > 70%. Patients too ill to undergo open heart surgery may undergo angioplasty with stenting.
• Low ejection fraction (<25%).
• Significant triple vessel coronary artery disease.
• Diabetic patients with significant stenosis in multiple coronary vessels.
• Presence of any associated severe valvular heart disease.

The prognosis of patients with unstable angina is greatly dependent on comorbidity, response to medication, time to diagnosis and treatment, presence of cardiogenic shock and type of therapeutic intervention. In general, patients with new ST-segment changes seen on the initial ECG have a worse prognosis compared to patients with isolated T-wave inversion. Over the years several negative prognostic factors have been identified for unstable angina patients and include the following:

• Heart failure which requires long term treatment.
• Hemodynamic instability that requires use of vasopressor agents.
• Low ejection fraction.
• Development of new or worsening of mitral insufficiency.
• Developing of recurrent angina.
• Development of ventricular tachycardia that requires use of antiarrhythmic agents.

In many patients with unstable angina who are on intense antianginal therapy, repeat attacks are not rare.

Causes and risk factors for unstable angina include the following:

• Atherosclerosis
• Family historic of coronary artery disease
• Smoking
• Diabetes mellitus
• Hyperlipidemia
• Sedentary life style
• Hypertension
• Obesity
• Elevated levels of homocysteine
• Metabolic syndrome

The metabolic syndrome is characterized by abdominal obesity (waist circumference > 40 inches for men and 35 inches in women), decreased HDL <40 mg/dl for men and <50 mg/dl in women, hypertriglyceridemia (> 150mg/dl) and hypertension (>130/85 mmHg). Patients suffering from the metabolic syndrome tend to have a 3-4 fold increased risk for development of coronary artery atherosclerosis and stroke compared to those who do not have this syndrome [4].

The incidence of unstable angina is on the increase globally based on stats from emergency rooms. In addition, there is a gross underestimate of the real numbers because many cases of unstable angina are not clinically recognized and other are managed in outpatient settings. Unstable angina typically presents in patients aged 60 and over. Women with unstable angina tend to be 5 years older and African Americans tend to presents at a slightly younger age than other races.

Unstable angina in women is frequently associated with comorbid disorders like diabetes, hypertension, congestive heart failure and a family history of coronary artery disease. Men on the other hand, tend to present with a history of prior myocardial infarction and/or coronary revascularization. Overall, unstable angina tends to have the worst outcomes in African Americans compared to other races.

The pathology of unstable angina is related to several factors that include the following:

• Cyclical flow of blood that does not meet demands of the heart. The cyclical flow of blood is related to episodes of vasospasm which may be triggered by a variety of factors.
• Disruption or rupture of an atherosclerotic plaque resulting in downstream occlusion or narrowing of a coronary artery.
• Mismatch in supply and demand of oxygen.
• Thrombosis in the coronary vessels.
• Vasoconstriction or spasm of a coronary vessel, in many cases the right coronary artery.

Conditions causing a mismatch of oxygen supply versus demand include the following:

• Arrhythmias like atrial fibrillation , ventricular tachycardia or ventricular fibrillation
• Heart disorders like congestive heart failure
• Mental health disorders like anxiety, stress, post traumatic stress disorder, panic attack
• Systemic disorders like pheochromocytoma, Cushing disease, thyrotoxicosis or Graves disease
• Use of illicit drugs like amphetamine, cocaine or methamphetamine
• Valvular heart disorders
• Vascular disorders like arteriovenous shunts or fistulas
• Anemia 
• Hypoxemia may be due to pulmonary embolism, sickle cell disease, carbon monoxide poisoining or cyanide toxicity 
• Polycythemia
• Hypotension from any cause can lead to decreased delivery of blood to the lungs for oxygenation

Once unstable angina has resolved, preventive steps should be encouraged [9]. It is important to wait at least 4-12 weeks to allow that risk of major adverse event to subside before making any sudden changes in the lives of these patients. Secondary prevention requires changes in lifestyle such as:

• Healthy diet
• Participating in exercise
• Lowering cholesterol
• Controlling blood sugar
• Discontinuation of smoking
• Limiting intake of alcohol
• Reducing body weight
• Taking statins
• Control of hypertension
• Limiting physical activity like shoveling snow in cold weather

One of the clinical spectrums of acute coronary syndrome (ACS) is unstable angina. Patients who have unstable angina present exactly like those who have myocardial ischemia or a myocardial infarction but they do not have elevated levels of cardiac enzyme in the blood. When worked up, these patients do not always have severe coronary disease but in fact tend to have coronary artery vasospasm. Often the chest pain is unresponsive to nitroglycerin and patients seek assistance in the emergency room. Even though unstable angina is not associated with elevated levels of cardiac biomarkers, it is a serious disorder that can be life threatening. The treatment involves the use of a variety of cardiac medications and in some cases, interventional therapy [1] [2] [3].

Unstable angina is a serious heart disorder that often presents with chest pain at rest. When the chest pain does not respond to nitroglycerin, it is highly recommended that the patient be seen in the emergency room. Unstable angina is very unpredictable and needs immediate medical attention.

Other common symptoms are: 

• Pain that radiates to the jaw, back or arm
• Nausea
• Vomiting
• Anxiety
• Sweating
• Shortness of breath
• Dizziness
• Fatigue

Patients may have a varied course in hospital ranging from a heart attack, heart failure or development of abnormal heart rhythm. Once the diagnosis is made, the treatment starts with medications to reduce angina symptoms and improve blood flow. Some patients may need procedure to open up the coronary vessels if there is a blockage. Prevention rests on a healthy low fat diet, discontinuation of smoking, regular exercise and compliance with medications.

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