Chronic stable angina overview


 * Associate Editors-In-Chief:

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.

Pathophysiology
Chronic stable angina results from one of three pathophysiologic processes:
 * Most commonly, chronic stable angina is due to fixed obstructive disease or atherosclerosis which involves the narrowing of the coronary arteries.
 * This narrowing results in an inadequate supply of blood and oxygen to meet the demands of myocardial metabolism. This supply/demand mismatch activates a molecular cascade of events that causes the release of molecules such as bradykinin and adenosine, which in turn stimulate the sympathetic and vagal afferent fibers, causing anginal pain.
 * Certain conditions can increase the myocardial oxygen demand secondary to an increase in cardiac output and can exacerbate chronic stable angina. These conditions include, but are not limited to; fever, thyrotoxicosis, anemia, emotional stress, and tachyarrythmias. This increase in cardiac demand is often treated with pharmacologic intervention of beta blockers or by intervention directed towards the underlying condition.


 * While fixed obstructive epicardial disease is the most common cause of chronic stable angina, vasospasm of the epicardial artery can also cause angina. Angina due to spasm of an epicardial artery is known as Prinzmetal's angina or variant angina. Prinzmetal's angina or variant angina is often treated with calcium channel blockers to relieve the spasm.


 * Chronic stable angina can also result from microvascular disease, known as microvascular angina or Syndrome X. Microvascular angina is often treated with calcium channel blockers to relieve the spasm.

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.

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.