Angina Pectoris

Objectives

Definitions

Angina pectoris is a syndrome characterized by chest pain resulting from an imbalance between oxygen supply and demand, and is most commonly caused by the inability of atherosclerotic coronary arteries to perfuse the heart under conditions of increased myocardial oxygen consumption. It may also occur in patients with seemingly normal coronary arteries subjected to acute or chronic increase in myocardial work, such as aortic stenosis, hypertension, or hypertrophic cardiomyopathy. Coronary artery spasm, superimposed upon normal or diseased arteries, can provoke pain in the absence of increased myocardial demands such as variant (Prinzmetal's) angina and some cases of stable or unstable angina. There is also a group of patients who have angina without demonstrable evidence of coronary artery disease.

 

Classification of Angina Pectoris

Once the history has indicated that chest pain is most likely angina, it has to be decided which of the several clinical syndromes of angina the patient manifests.

Character: More often described as a discomfort, pressure, or squeezing sensation. Less commonly as burning, sticking, or sharp.

Location: Most often in the substernal area, precardium, or epigastrium with radiation to the left arm, jaw, or neck. Less commonly felt only in radiation areas and not in the chest.

Precipitation: Often provoked by exertion, emotion, exposure to cold, eating (4 "E"s), or smoking, and relieved by rest, removal of provoking factors, or sublingual nitrates.

Duration: Usually lasts a few minutes, rarely over 20-30 minutes.

The frequency and severity of the symptoms change little with daily activities, and pain does not usually occur at rest.

Unstable angina pectoris is probably not a single entity, but a combination of syndromes which have been referred to by various names, such as preinfarction angina, impending myocardial infarction, progressive or crescendo angina, coronary insufficiency, new onset angina, etc.

Unstable angina pectoris usually presents in one of three patterns:

Variant Angina Pectoris (Prinzmetal's Angina)

This type of angina results from transmural myocardial ischemia caused by coronary artery spasm and may occur in patients with or without coronary atherosclerosis. Pain occurs principally at rest, usually unprovoked, but since coronary artery disease may coexist, pain may also be provoked by exercise. The pain may occur in a circadian manner, often in the early morning hours. The pain is associated with ST-segment elevation, in contrast to typical angina pectoris. Often subclinical (painless) episodes occur with ST- segment elevations, often associated with arrhythmias, or bundle branch block.

 

Evaluation

The diagnosis of angina pectoris is established by obtaining a reliable description of the chest discomfort and its relationship to activity. The likelihood of coronary artery disease is enhanced by age, history of hyper-tension, hyperlipidemia, smoking, diabetes mellitus, or a family history of ischemic heart disease in first degree relatives.

Though often normal, the physical examination may supply important information that will affect evalua-tion: the appearance of the patient, especially in an episode of pain; xanthelasmia; hypertension; evi-dence of peripheral arterial disease; tenderness of the chest wall suggest-ing pain of musculoskeletal origin; abnormal pulsations on palpation over precardium; basilar rales; an S4, especially during pain; murmurs of aortic stenosis, IHSS, mitral valve prolapse; or arrhythmias.

Basic screening for anemia, polycythemia, hyperglycemia, hyperlipidemia, etc. A resting ECG is often normal in stable angina pectoris in the absence of a previous MI or a cause for LVH. During pain the ECG may show transient ST- segment depression, T wave inversion, and/or ventricular arrhythmia. Abnormal ECG changes are more common with unstable angina pectoris. ST-segment eleva-tion rather than depression occurs during attack in variant angina. Especially with 2D echocardiogra-phy, the assessment of left ventricu-lar wall motion, volume, and ejection fraction is feasible, as is detection of IHSS, AS, and LVH. Most, but not all, physically able patients with stable angina pectoris should have an exercise stress test as it is very helpful in reproducing symptoms, documenting ischemic ECG changes, and assessing the level of severity. Patients with high grade coronary artery disease may manifest inability to elevate the heart rate or blood pressure during exer-cise, or develop marked ST-changes at low level exercise. Exercise-induced arrhythmias or left ventricu-lar dysfunction provide diagnostic information with important therapeu-tic potential. The exercise stress test may be combined with echocardio-graphy (Echo Stress Test) for more specificity. This is particularly useful in females, as they tend to have a higher rate of false positive tests. Ambulatory monitoring with equip-ment designed to show ST-T changes is useful in some cases and is especially good for detecting silent ischemia. Radionuclide scintigraphy enhances the sensitivity and specificity of the exercise stress test. The patient with a normal ECG at rest may require only a standard exercise test. If ab-normal at rest, such as ST-T abnor-malities or LBBB, etc., the patient is best evaluated with Thalium scinti-graphy performed during the exer-cise stress test. Nuclear ventriculo-gram using tecnetium Tc 99 m tagged to the patient's RBCs permits evaluation of left ventricular wall motion and measurement of ejection fraction. Although not necessary for the diagnosis of coronary artery disease in most instances, cardiac catheteri-zation and coronary angiography is the "court of last resort" for evalua-ting patients with chest pain. It is the only currently available diagnostic test that depicts coronary anatomy and defines the extent of the coro-nary artery disease. It is a necessary procedure for all patients who are potential surgical candidates. How-ever, not all patients with angina pectoris require surgical therapy, and thus not all are in need of arterio-graphy. A logical approach to the work-up should be undertaken, reserving angiography for those patients who are potential surgical candidates or for the unusual patient in whom the cause of chest pain is unknown after non-invasive study.

Some of the usual indications for coronary arteriography in angina pectoris include:

Management
Table 1. General Therapeutic Considerations
Risk factor reduction: Discontinue smoking, control hypertension 
and diabetes, lower hyperlipidemia, and maintain an ideal body weight. 
Work adjustment, stress reduction, and behavioral modification.
Exercise: The prescription for exercise must be made carefully with the 
knowledge of each individual patient taken into consideration. 

The drugs most frequently used in the treatment of stable angina pectoris are the nitrates, the beta blockers, and the calcium channel blockers.

Some patients with very mild, stable angina pectoris get along very well by adhering to the general therapeutic measures stated above, and using an occasional sublingual nitroglycerine tablet PRN. Some patients also do well on a regular dose of a long-acting nitrate, and sublingual TNT PRN. Some authorities feel that no one agent can adequately control significant angina, and initiate treatment using two or more different agents. Selecting which drug to employ and in what dosage depends on the severity of the angina and associated conditions.

For routine patients with no other problems, a good regimen would be a nitrate and a beta blocker. For patients with asthma, CHF, or insulin-dependent diabetes mellitus, the beta-blockers are relatively con-traindicated and a calcium channel blocker should be employed. Some patients do not respond to the nitrates and beta blockers, and some do not tolerate nitrates or beta blockers because of side effects, so calcium channel blockers are added or sub-stituted respectively. Some physicians prefer to start the patient on calcium channel blockers as initial therapy. Some patients may require all three medications, and occasionally combinations of calcium channel blockers are used.

Transluminal coronary angioplasty has become an accepted method of treating selected patients with angina due to atheromatous coronary artery disease. This procedure is particular-ly useful in patients with single or double vessel disease, especially for lesions of the left anterior descending coronary artery. Coronary artery bypass grafting can provide significant relief from angina in over 80% of patients with disab-ling angina and has a low operative mortality. Since it neither reverses the disease process nor assures per-manent revascularization, its use is limited to those patients who cannot be managed medically, those with markedly abnormal ECG response to exercise, and those found to have significant left main coronary steno-sis or significant proximal lesions in all three coronary arteries. Hospitalization with bed rest, nasal O2, and sedation in an ECG-moni-tored environment is indicated for almost all patients with unstable an-gina. Most patients with unstable angina will respond to medical man-agement and can then be evaluated for extent of severity with the diag-nostic tests used for stable angina. A small percentage will fail to respond to medical management and will pro-ceed to myocardial infarction. Ano-ther small percentage will remain unstable with unremitting pain, and will require more aggressive management. More than 30% to 40% of medically treated patients will have PTCA or CABG surgery. Once the diagnosis is suspected, obtaining an ECG during pain is paramount. Variant angina is not a benign syndrome. Myocardial infarction can occur in the region affected by the coronary artery spasm in about 25% of patients, and either heart block or ventricular fibrillation can occur during an episode of spasm.
Table 2. Drugs
Nitrate Sublingual nitrates usually reverse spasm within 30-60 seconds. Oral or tropical 
nitrates can reduce the frequency of attacks. However, nitrates are not always 
successful, and abrupt withdrawal can provoke spasm. so it is important to taper 
off regardless of their seeming ineffectiveness. 
Calcuim Channel Blockers Effective in 60%-75% of patients, with or without nitrates.
Beta Blockers Beta Blockers are ususally ineffective and may actually be deleterious in variant angina.
Variant angina is usually not amenable to PTCA or CABG surgery except in select cases with fixed subtotal obstructions which are the site of reproducible superimposed spasm.


B. Pope, MD
updated 8/30/05


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