Chronic stable angina overview

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Overview
Historical Perspective
Classification
Classic Chronic Stable Angina
Atypical Walk through Angina Mixed Angina Nocturnal Angina Postprandial Angina Cardiac Syndrome X Vasospastic Angina
Differentiating Chronic Stable Angina from Acute Coronary Syndromes
Pathophysiology
Epidemiology and Demographics
Risk Stratification
Pretest Probability of CAD in a Patient with Angina
Prognosis
Diagnosis
History and Symptoms
Physical Examination
Test Selection Guideline for the Individual Basis
Laboratory Findings
Electrocardiogram
Exercise ECG
Chest X Ray
Myocardial Perfusion Scintigraphy with Pharmacologic Stress
Myocardial Perfusion Scintigraphy with Thallium
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Alternative Therapies for Refractory Angina
Transmyocardial Revascularization (TMR)
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Enhanced External Counter Pulsation (EECP)
ACC/AHA Guidelines for Alternative Therapies in patients with Refractory Angina
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Guidelines for Asymptomatic Patients
Noninvasive Testing in Asymptomatic Patients
Risk Stratification by Coronary Angiography
Pharmacotherapy to Prevent MI and Death in Asymptomatic Patients
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Maheep Singh Sangha, M.B.B.S.; Cafer Zorkun, M.D., Ph.D. [2]

Overview

Angina pectoris, commonly known as angina, is chest pain due to ischemia (a lack of blood and subsequent lack of oxygen supply) of the heart muscle. It is most often due to obstruction or spasm of the coronary arteries (the heart's blood vessels). Coronary artery disease, also referred to as atherosclerosis of the coronary arteries, is the most common cause of angina. The term derives from the Greek ankhon ("strangling") and the Latin pectus ("chest") meaning "a strangling feeling in the chest". In angina pectoris, symptomatic onset may include chest discomfort indicated by a feeling of tightness, heaviness, or pain in the chest cavity.

Historical Perspective

Chronic stable angina is a form of chest pain characterized by an insufficient blood flow to the myocardium of the heart to match myocardial energy demands (ischemia). The term angina was originally derived from the Greek word ankhon and the Latin word pectus, which when combined, loosely translates as "a strangling feeling in the chest." Attempts to classify this disease state began as early as the 4th century B.C., when Lucius Annaeus Seneca first described the symptoms he was experiencing as "to have any other malady is to be sick; to have this is to be dying." Throughout history many renowned researchers and health care professionals have contributed to the understanding, definition, and recognition of angina.

Classification

Chronic Stable Angina

Angina pectoris is a sensation of chest discomfort that is often described as: a feeling of tightness, heaviness, or pain. Angina pectoris is a characteristic of coronary heart disease. When it occurs chronically, this is referred to as stable angina.

Walk Through Angina

Walk through angina is the appearance of anginal chest discomfort early in the course of exertion which subsequently subsides despite continued exertion.

Mixed Angina

Mixed or variable threshold angina pectoris is a syndrome in which there is substantial variation in the magnitude of physical activity that induces anginal chest pain.

Nocturnal Angina

Nocturnal angina is the occurrence of anginal discomfort either during the first hours of sleep or during the early morning hours. It is speculated that discomfort caused during the first hours of sleep is due to increased venous return, whereas the discomfort caused during the early morning hours is due to increased vascular tone.

Postprandial Angina

Postprandial angina pectoris is anginal chest discomfort that occurs following meals. It is thought to be due to an increase in vascular tone or a reduction in coronary blood flow.

Syndrome X

Syndrome X may refer to cardiac syndrome X, metabolic syndrome and single X syndrome, where an individual has a single X chromosome, typically described as turner syndrome. The otherwise unidentifiable rare disease afflicting Brooke Greenberg and only about half a dozen other people in the world.

Vasospastic Angina

Coronary vasospasm is a multi-factorial, transient, and abrupt reduction of luminal diameter of an epicardial coronary artery due to inappropriate constriction of coronary smooth muscle that can generate distal ischemia. This may occur spontaneously or in the context of angioplasty, particularly if denudation of the endothelium or dissection occurs. In addition, the vasospasm can either be focal or multifocal (which compromises more than one vessel).

Differentiating Chronic Stable Angina from Urgent Conditions

Stable angina must be differentiated from unstable angina and acute coronary syndromes. If the pattern of angina is stable, this is termed chronic stable angina. If the magnitude, threshold or frequency of chest pain accelerates, this is termed an acute coronary syndrome.

Pathophysiology

The primary causes of myocardial ischemia in chronic stable angina are: fixed epicardial stenosis, spasm of the epicardial artery and/or microvascualar disease. The causation of angina is not mutually exclusive. Two or more causes may coexist in the same patient.

Epidemiology and Demographics

Coronary artery disease (CAD) remains the single leading cause of death in the United States. Stable angina is the initial manifestation of ischemic heart disease in approximately 50% of these patients.

Risk Stratification

The average mortality in patients with stable angina ranges from 1-3%. However, the prognosis varies widely depending on various factors such as: the duration and severity of symptoms, resting ECG abnormalities, abnormal left ventricular function and associated comorbidities.

Pretest Probability

Pretest probability is defined as the probability of the target disorder before the result of a diagnostic test is known. A number of studies have emphasized the importance of pretest probability of coronary artery disease (CAD). Once a thorough patient history and physical examination is complete, it is important to assess the probability of underlying CAD, as this helps both the physician and the patient to determine the next step in the diagnosis and treatment. In patients with chronic stable angina, the strongest predictors contributing to underlying significant CAD include: the age, gender and type of pain (typical, atypical) experienced.

Diagnosis

History and Symptoms

The name 'angina pain' can be thought of as a misnomer as patients often describe the sensation as discomfort rather than physical pain. The best method to characterize this discomfort/pain is through the 'PQRST system'.

Physical Examination

Among patients with chronic stable angina, the physical examination may be asymptomatic or characteristically normal. Patients that present with left ventricular dysfunction are associated with a poorer prognosis than patients who do not present with dysfunction. All patients should be examined carefully for the presence of rales and other signs of heart failure.

Test Selection Guideline for the Individual Basis

Criteria for test selection hinges largely on the current disease state of the individual patient and subsequent level of fitness for testing. Potential diagnostic testing modalities include: exercise ECG, ECG at rest, exercise echocardiography, echocardiography at rest, and stress scintigraphy.

Laboratory Findings

In patients with chronic stable angina, initial laboratory investigations are used to: identify potential causes of ischemia, establish risk factors, and determine the overall prognosis for the patient. An initial laboratory test can provide a wide variety of clinical information. For instance, low hemoglobin levels can cause ischemia. Therefore, assessing hemoglobin as a part of complete blood count provides prognostic information. Biomarkers, such as troponin and CK-MB, are used to exclude myocardial injury. In assessment for risk factor stratification, all patients with ischemic heart disease are recommended to have a a standard round of blood work conducted including fasting plasma glucose levels and a complete lipid profile. Serum creatinine is used to assess renal dysfunction due to associated hypertension or diabetes and remains a negative prognostic factor. In patients with chronic stable angina, an elevation in fasting glucose independently predicts the adverse outcome. Recent research on NT-pro-BNP has demonstrated the ability to predict long-term mortality in patients with chronic stable angina independent of age, ventricular ejection fraction and other risk factors.

Electrocardiography

A resting 12-lead ECG is performed and recorded in all patients with suspected angina pectoris. However, a normal resting ECG does not exclude the diagnosis of ischemia. Abnormalites commonly observed on resting ECG include: ST-segment changes, left ventricular hypertrophy (LVH), left branch bundle blockage (LBBB), signs of coronary artery disease (CAD) such as previous myocardial infarction (MI) or abnormal repolarization patterns. An ECG recorded during pain helps to identify an underlying vasospasm.

Clinical Presentation

The majority of patients present with history of either, chest pain or discomfort categorized as: typical or atypical. Typical presentation would include pain or discomfort in the front or anterior precordium. Atypical presentation can be more convoluted in presentation and involve a wide range of symptoms. For example, an atypical patient may present with dyspnea instead of chest pain and this is termed an angina equivalent.

In addition to the historical presentation of chest pain or discomfort, the patient history should be extensively evaluated to include an assessment of cardiovascular risk factors. Physical examination may be normal or asymptomatic. In some cases, a physical examination may reveal heart failure. Additional findings can be important in understanding the onset of the condition. For instance, the presence of peripheral vascular disease may be associated with an increased risk of coronary artery disease (CAD).

Pretest Probability of Coronary Artery Disease

Pretest probability is the probability of a given disorder before the result of the diagnostic test(s) are known. In the case of angina, the initial history and physical examination can help categorize the patient into a low, intermediate or high probability group. Assessment of the pretest probability of disease aids in the selection of diagnostic studies and in the initiation of treatment.

Diagnostic tests

Initial Studies

• The goal of initial testing is to exclude the presence of an acute coronary syndrome such as ST elevation MI, non ST elevation MI and unstable angina. Therefore, an electrocardiogram is performed in the patient who first presents with chronic stable angina.
• The EKG may be normal in the majority of cases if ischemia is not present at the time the EKG is obtained.
• Other relevant findings would include evidence of left ventricular hypertrophy, or Q waves in multiple leads suggestive of old MI.

Exclusion of Factors That Would Exacerbate A Supply Demand Mismatch

In the patient who first presents with unstable angina a hemoglobin, hematocrit, and TSH should be obtained to exclude factors that would exacerbate a supply demand mismatch.

Studies to Aid in the Management of Chronic Risk Factors

This includes lab tests like a lipid profile and the assessment of the Hb a1C and glucose.

Imaging Studies and Studies to Assess the Magnitude of Ischemia

• A chest x ray is often performed to assess for the presence of cardiomegaly and congestive heart failure.

• Specific cardiac tests for angina include exercise ECG testing, myocardial perfusion imaging, echocardiography, stress echocardiography and coronary angiography.

Diagnostic Criteria

To confirm or qualify for the diagnosis of chronic stable angina, at least one of the following additional criteria for coronary artery disease and/or ischemia must be present:

• New and/or dynamic ST-depression >0.05 mV, ST-elevation >0.1 mV, or symmetric T wave inversion >0.2 mV on a resting ECG

• Definite evidence of ischemia on stress echocardiography, myocardial scintigraphy (e.g. an area of clear reversible ischemia), or ECG-only stress test (e.g., significant dynamic ST shift, horizontal or downsloping)

• Angiographic evidence of epicardial coronary artery stenosis of >70% diameter reduction and/or evidence for intraluminal arterial thrombus.

Treatment

• Treatment for chronic stable angina includes:

• Lifestyle modification
• Pharmacotherapy
• Revascularization procedures(percutaneous coronary intervention (PCI), coronary artery bypass surgery (CABG)).

• It is also important to identify any exacerbating factors like anemia, thyrotoxicosis, valvular heart disease or decompensated heart failure and treat them.

• Smoking cessation counseling, diet and weight management, promoting physical exercise, blood pressure and diabetes control are all components of risk factor modifications and should be stressed at each clinic visit.

• Specific medical therapy includes antiplatelets (like ASA, clopidogrel), antianginals (like nitrates, beta blockers, calcium channel blockers, lipid-lowering agents, ACE inhibitors and angiotensin receptor blocking agents.

• Coronary revascularization is recommended when optimal medical therapy has failed to reduce symptoms or severe atherosclerotic disease or high risk criteria on noninvasive testing.

• Options available for revascularization include: percutaneous coronary intervention PCI and coronary artery bypass grafting CABG.
• In patients with chronic stable angina, the factors influencing the choice of coronary revascularization therapy (percutaneous coronary intervention or coronary artery bypass surgery) are varied and complex. The severity of symptoms, lifestyle, extent of objective ischemia, and underlying risks must be weighed against the benefits of revascularization and the patient’s preference, as well as local availability and expertise.
• Evidence from randomized trials and large revascularization registers can guide these decisions.
• In the past decade there has been significant improvements in medical treatment, bypass surgery and percutaneous coronary intervention.

Prognosis of Chronic Stable Angina

Ischemic heart disease remains as the number one cause of mortality in developed countries. The prognosis of stable angina varies widely depending on severity of symptoms, extent of atherosclerosis and presence of other risk factors and co-morbidities. The presence of impaired left ventricular function is associated with a poor prognosis.