angina pectoris

This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (November 2007)

Angina pectoris, commonly known as angina, is severe chest pain^[1] due to ischemia (a lack of blood and hence oxygen supply) of the heart muscle, generally due to obstruction or spasm of the coronary arteries (the heart's blood vessels). Coronary artery disease, the main cause of angina, is due to atherosclerosis of the cardiac arteries. The term derives from the Latin angina ("infection of the throat") from the Greek ἀγχόνη ankhone ("strangling"), and the Latin pectus ("chest"), and can therefore be translated as "a strangling feeling in the chest".

It is not common to equate severity of angina with risk of fatal cardiac events. There is a weak relationship between severity of pain and degree of oxygen deprivation in the heart muscle (i.e., there can be severe pain with little or no risk of a heart attack, and a heart attack can occur without pain).

Worsening ("crescendo") angina attacks, sudden-onset angina at rest, and angina lasting more than 15 minutes are symptoms of unstable angina (usually grouped with similar conditions as the acute coronary syndrome). As these may herald myocardial infarction (a heart attack), they require urgent medical attention and are generally treated as a presumed heart attack.

Symptoms

Most patients with angina complain of chest discomfort rather than actual pain: the discomfort is usually described as a pressure, heaviness, tightness, squeezing, burning, or choking sensation. Apart from chest discomfort, anginal pains may also be experienced in the epigastrium (upper central abdomen), back, neck area, jaw, or shoulders. This is explained by the concept of referred pain, and is due to the spinal level that receives visceral sensation from the heart simultaneously receiving cutaneous sensation from parts of the skin specified by that spinal nerve's dermatome, without an ability to discriminate the two. Typical locations for referred pain are arms (often inner left arm), shoulders, and neck into the jaw. Angina is typically precipitated by exertion or emotional stress. It is exacerbated by having a full stomach and by cold temperatures. Pain may be accompanied by breathlessness, sweating and nausea in some cases. It usually lasts for about 3 to 5 minutes, and is relieved by rest or specific anti-angina medication. Chest pain lasting only a few seconds is normally not angina.

Myocardial ischemia comes about when the myocardia (the heart muscles) receive insufficient blood and oxygen to function normally either because of increased oxygen demand by the myocardia or by decreased supply to the myocardia. This inadequate perfusion of blood and the resulting reduced delivery of oxygen and nutrients is directly correlated to blocked or narrowed blood vessels.

Some experience "autonomic symptoms" (related to increased activity of the autonomic nervous system) such as nausea, vomiting and pallor.

Major risk factors for angina include cigarette smoking, diabetes, high cholesterol, high blood pressure, sedentary lifestyle and family history of premature heart disease.

A variant form of angina (Prinzmetal's angina) occurs in patients with normal coronary arteries or insignificant atherosclerosis. It is thought to be caused by spasms of the artery. It occurs more in younger women.

Subtypes

Stable angina

This refers to the more common understanding of angina related to myocardial ischemia. Typical presentations of stable angina is that of chest discomfort and associated symptoms precipitated by some activity (running, walking, etc) with minimal or non-existent symptoms at rest. Symptoms typically abate several minutes following cessation of precipitating activities and resume when activity resumes. In this way, stable angina may be thought of as being similar to claudication symptoms.

Unstable angina

Unstable angina (UA) is defined as angina pectoris that changes or worsens.^[1]

It has at least one of these three features:

1. it occurs at rest (or with minimal exertion), usually lasting >10 min;
2. it is severe and of new onset (i.e., within the prior 4–6 weeks); and/or
3. it occurs with a crescendo pattern (i.e., distinctly more severe, prolonged, or frequent than previously).

UA may occur unpredictably at rest which may be a serious indicator of an impending heart attack. What differentiates stable angina from unstable angina (other than symptoms) is the pathophysiology of the atherosclerosis. In stable angina, the developing atheroma is protected with a fibrous cap. This cap (atherosclerotic plaque) may rupture in unstable angina, allowing blood clots to precipitate and further decrease the lumen of the coronary vessel. This explains why an unstable angina appears to be independent of activity.

Diagnosis

In angina patients who are momentarily not feeling any one chest pain, an electrocardiogram (ECG) is typically normal, unless there have been other cardiac problems in the past. During periods of pain, depression or elevation of the ST segment may be observed. To elicit these changes, an exercise ECG test ("treadmill test") may be performed, during which the patient exercises to their maximum ability before fatigue, breathlessness or, importantly, pain supervenes; if characteristic ECG changes are documented (typically more than 1 mm of flat or downsloping ST depression), the test is considered diagnostic for angina. The exercise test is also useful in looking for other markers of myocardial ischaemia: blood pressure response (or lack thereof, particularly a drop in systolic pressure), dysrhythmia and chronotropic response. Other alternatives to a standard exercise test include a thallium scintigram (in patients that cannot exercise enough for the purposes of the treadmill tests, e.g., due to asthma or arthritis or in whom the ECG is too abnormal at rest) or Stress Echocardiography.

In patients in whom such noninvasive testing is diagnostic, a coronary angiogram is typically performed to identify the nature of the coronary lesion, and whether this would be a candidate for angioplasty, coronary artery bypass graft (CABG), treatment only with medication, or other treatments. In patients who are in hospital with unstable angina (or the newer term of "high risk acute coronary syndromes"), those with resting ischaemic ECG changes or those with raised cardiac enzymes such as troponin may undergo coronary angiography directly.

Pathophysiology

Increase in heart rate results in increased oxygen demand by the heart. The heart has a limited ability to increase its oxygen intake during episodes of increased demand. Therefore, an increase in oxygen demand by the heart (eg, during exercise) has to be met by a proportional increase in blood flow to the heart.

Myocardial ischemia can result from:

1. a reduction of blood flow to the heart that can be caused by stenosis, spasm, or acute occlusion (by an embolus) of the heart's arteries
2. resistance of the blood vessels
3. reduced oxygen-carrying capacity of the blood.

Atherosclerosis is the most common cause of stenosis (narrowing of the blood vessels) of the heart's arteries and, hence, angina pectoris. Some people with chest pain have normal or minimal narrowing of heart arteries; in these patients, vasospasm is a more likely cause for the pain, sometimes in the context of Prinzmetal's angina and syndrome X.

Myocardial ischemia also can be the result of factors affecting blood composition, such as reduced oxygen-carrying capacity of blood, as seen with severe anemia (low number of red blood cells), or long-term smoking.

Epidemiology

Roughly 6.3 million Americans are estimated to experience angina. Angina is more often the presenting symptom of coronary artery disease in women than in men. The prevalence of angina rises with an increase in age. Similar figures apply in the remainder of the Western world. All forms of coronary heart disease are much less-common in the Third World, as its risk factors are much more common in Western and Westernized countries; it could therefore be termed a disease of affluence. The adoption of a rich, Westernized diet and subsequent increase of smoking, obesity and other risk factors, as chronicled in The China Study, has already led to an increase in angina and related diseases in countries such as China.

Recently, angina was tied to exposure of Bisphenol-A^[2] among adults in the US.

Treatment

The main goals of treatment in angina pectoris are relief of symptoms, slowing progression of the disease, and reduction of future events, especially heart attacks and, of course, death. Low-dose aspirin decreases the risk of heart attack in patients with chronic stable angina that have no contraindications to aspirin therapy.^[3] Beta blockers (e.g., carvedilol, propranolol, atenolol) have a large body of evidence in morbidity and mortality benefits (fewer symptoms, less disability and longer life) and short-acting nitroglycerin medications are used for symptomatic relief of angina^{[citation needed]}. Calcium channel blockers (such as nifedipine (Adalat) and amlodipine), isosorbide mononitrate and nicorandil are vasodilators commonly used in chronic stable angina^{[citation needed]}. A new therapeutic class, called If inhibitor, has recently been made available: ivabradine provides pure heart rate reduction^[4] leading to major anti-ischemic and antianginal efficacy. ACE inhibitors are also vasodilators with both symptomatic and prognostic benefit and, lastly, statins are the most frequently used lipid/cholesterol modifiers which probably also stabilize existing atheromatous plaque^{[citation needed]}.

Surprising perhaps is that exercise is also a very good long term treatment for angina (but only particular regimens - gentle and sustained exercise rather than dangerous intense short bursts),^[5] probably working by complex mechanisms such as improving blood pressure and promoting coronary artery collateralisation.

Identifying and treating risk factors for further coronary heart disease is a priority in patients with angina. This means testing for elevated cholesterol and other fats in the blood, diabetes and hypertension (high blood pressure), encouraging stopping smoking and weight optimisation.

Ranolazine (Ranexa) is a new class of anti-anginal drug that was approved by the Food and Drug Administration (FDA)^{[citation needed]}

Recently, University of Cincinnati medical researchers in cardiology have tried to use a non-invasive, non-surgical collecting tool to gather harvested erythropoietic bone marrow-based adult stem cells and coax them into regrowing new coronary blood vessels to supply the cardiac muscle's cells (cardiac myocytes) with oxygenated blood, with some success- leading to larger Phase 2 trials.^{[citation needed]}

The largest randomised trial of an anti-anginal drug to date is the ACTION trial. It included 7,665 patients with stable angina pectoris. ACTION demonstrated that the calcium channel blocker nifedipine (Adalat) prolongs cardiovascular event- and procedure-free survival in patients with coronary artery disease. New overt heart failures were reduced by 29% compared to placebo; however, the mortality rate difference between the two groups was statistically insignificant. This finding confirms the vascular-protective effects of nifedipine.^[6]

Although zinc is not currently used to treat angina pectoris, there are reports documenting its beneficial effects. A report of zinc to treat angina pectoris as early in 1899 has been found.^[7] A review of the literature by Eby and Halcomb^[8] showed that: Administration of zinc sulfate was a beneficial treatment in patients with severely symptomatic, inoperable atherosclerotic disease. There was no difference in zinc concentration between patients with and without atherosclerosis in whole blood, erythocytes or hair, but there was a major difference between normal aorta and diseased aortas. Zinc was also effective in both angina pectoris and Raynaud's disease. Environmental exposure to zinc in Polish mines resulted in a 40% reduction in the incidence of angina compared with non miners. Lead had no effect while cadmium exposure resulted in more than tripling the incidence of angina of effort. There is evidence that zinc can provide antiatherogenic properties by preventing metabolic physiologic derangements of the vascular endothelium. Because of its antioxidant and cell-plasma membrane-stabilizing properties, zinc appears to be crucial for the protection against cell-destabilizing agents such as polyunsaturated lipids and inflammatory cytokines. Zinc also may be antiatherogenic by interfering with signaling pathways involved in apoptosis. Certain lipids and zinc deficiency may potentiate the cytokine-mediated inflammatory response and endothelial cell dysfunction in atherosclerosis. As people grow older, they may ingest less zinc and absorption of zinc from the diet may falter. Angina pectoris may result from zinc deficiency. The main source of zinc in the diet is meat, and patients are routinely advised to reduce their consumption of meat due to concerns about cholesterol. Reflecting a shortage of zinc in the diet, the RDA for zinc has been recently reduced. Therapeutic dosages of bioavailable zinc for angina have been reported to be 60 mg of zinc three times per day up to 300 mg per day for no longer than 2 weeks (due to the risk of inducing copper deficiency) and copper supplementation is also advised. This benefit is reminiscent of magnesium treatment of variant angina.

As shown by Jenner et al.,^[9] zinc supplementation did not significantly alter the increase in total plasma cholesterol levels observed in rabbits fed high cholesterol. However, in cholesterol fed rabbits zinc supplementation significantly reduced the accumulation of total cholesterol levels in aorta which was accompanied by a significant reduction in average aortic lesion cross sectional areas of the animals. Elevated levels of cholesterol oxidation products (5,6- a and b cholesterol epoxides, 7b-hydroxycholesterol, 7-ketocholesterol) in aorta and total F2-isoprostanes in plasma and aorta of rabbits fed cholesterol diet were significantly decreased by zinc supplementation. Their data indicated that zinc has an anti-atherogenic effect, possibly due to a reduction in iron-catalysed free radical reactions.

History

The concept of Hritshoola—literally heart pain—was known to Sushruta (6th century BCE).^[10] Dwivedi & Dwivedi (2007)—on the condition described by Sushruta—hold that: 'It embodies all the essential components of present day definition, i.e. site, nature, aggravating and relieving factors and referral. According to him angina is chest pain which is precordial, temporary, exertional, emotional, burning like and relieved by rest. He also linked this kind of pain to obesity (medoroga).'^[10]

References

Major studies

• Information on ACTION - A Coronary Disease Trial Investigating Outcome with Nifedipine GITS in Patients with chronic stable angina pectoris

External links

• British Heart Foundation - Angina
• Angina Pectoris Animation Video 3D
• Medpedia: Angina Pectoris