Prinzmetal's angina
Encyclopedia
Prinzmetal angina, also known as variant angina or angina inversa, is a syndrome typically consisting of angina (cardiac chest pain) at rest that occurs in cycles. It is caused by vasospasm
, a narrowing of the coronary arteries caused by contraction of the smooth muscle tissue in the vessel walls rather than directly by atherosclerosis
(buildup of fatty plaque and hardening of the arteries). It occurs more in younger women.
of a major coronary artery, but this is often mild or not in proportion to the degree of symptoms.
Prinzmetal's should be suspected by a cardiologist when the pain occurs at rest and/or in clusters, and in the absence of a positive treadmill stress test, as Prinzmetal's is exercise tolerant and can generally only be diagnosed after other forms of cardiac disease have been ruled out.
It is associated with specific ECG changes (elevation rather than depression of the ST segment). However, in order to be diagnosed, these ECG changes can only be tracked when the electrocardiogram occurs while the patient is experiencing an attack. Therefore, many experts recommend provocative testing during Electrocardiogram testing to attempt to induce an attack when Prinzmetal's is suspected.
of the coronary arteries.
It has been proposed that vasospastic angina is associated with enhanced contractility of coronary vascular smooth muscle due to reduced nitric oxide bioavailability caused by a defect in the endothelial nitric oxide synthethase enzyme which leads to endothelial function abnormalities.
Acetylcholine
is normally released by the parasympathetic nervous system
(PSNS) at rest, and causes dilation of the coronary arteries. While acetylcholine induces vasoconstriction of vascular smooth muscle cells through a direct mechanism, acetylcholine also stimulates endothelial cells to produce nitric oxide
(NO). NO then diffuses out of the endothelial cells, stimulating relaxation of the nearby smooth muscle cells. In healthy arterial walls, the overall indirect relaxation induced by acetylcholine (via nitric oxide) is of greater effect than any contraction that is induced.
When the endothelium is dysfunctional, stimulation with acetylcholine will fail to produce, or produce very little, nitric oxide. Thus, acetylcholine released by the PSNS at rest will simply cause contraction of the vascular smooth muscle. It is potentially by this mechanism that Prinzmetal's angina occurs.
Thromboxane
, a vasoconstrictor with a role in platelet aggregation, may also play a role in Prinzmetal's angina. Lipoprotein(a) interferes with fibrinolysis by competing with plasminogen. The impaired fibrinolysis triggers thrombus formation, which also results in coronary vasospasm in variant angina.
isoenzymes or troponin
I or T. These may or may not show a degree of positivity, as coronary spasm too can cause myocardial damage or may leave the arteries undamaged. Echocardiography
or thallium scintigraphy is often performed.
The gold standard
is coronary angiography with injection of provocative agents into the coronary artery. Rarely, an active spasm can be documented angiographically (e.g. if the patient receives an angiogram with intent of performing a primary coronary intervention with angioplasty
). Depending on the local protocol, provocation testing may involve substances such as ergonovine
, methylergonovine
or acetylcholine
. Exaggerated spasm is diagnostic of Prinzmetal angina.
ECG finding will more often show ST segment
elevation than ST depression. Elevation ST-segment in II, III and aVf.
s and calcium channel blocker
s.
Vasospasm
Vasospasm refers to a condition in which blood vessels spasm, leading to vasoconstriction. This can lead to tissue ischemia and death . Cerebral vasospasm may arise in the context of subarachnoid hemorrhage. Symptomatic vasospasm or delayed cerebral ischemia is a major contributor to...
, a narrowing of the coronary arteries caused by contraction of the smooth muscle tissue in the vessel walls rather than directly by atherosclerosis
Atherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
(buildup of fatty plaque and hardening of the arteries). It occurs more in younger women.
Eponym
It was first described as "A variant form of angina pectoris" in 1959 by the American cardiologist Dr. Myron Prinzmetal (1908–1987).Features
Symptoms typically occur at rest, rather than on exertion (thus attacks usually occur at night). Two-thirds of patients have concurrent atherosclerosisAtherosclerosis
Atherosclerosis is a condition in which an artery wall thickens as a result of the accumulation of fatty materials such as cholesterol...
of a major coronary artery, but this is often mild or not in proportion to the degree of symptoms.
Prinzmetal's should be suspected by a cardiologist when the pain occurs at rest and/or in clusters, and in the absence of a positive treadmill stress test, as Prinzmetal's is exercise tolerant and can generally only be diagnosed after other forms of cardiac disease have been ruled out.
It is associated with specific ECG changes (elevation rather than depression of the ST segment). However, in order to be diagnosed, these ECG changes can only be tracked when the electrocardiogram occurs while the patient is experiencing an attack. Therefore, many experts recommend provocative testing during Electrocardiogram testing to attempt to induce an attack when Prinzmetal's is suspected.
Mechanism
The mechanism that causes such intense vasospasm, as to cause a clinically significant narrowing of the coronary arteries is, as of yet, unknown. It is hypothesized, however, to be related to dysfunction of the endotheliumEndothelium
The endothelium is the thin layer of cells that lines the interior surface of blood vessels, forming an interface between circulating blood in the lumen and the rest of the vessel wall. These cells are called endothelial cells. Endothelial cells line the entire circulatory system, from the heart...
of the coronary arteries.
It has been proposed that vasospastic angina is associated with enhanced contractility of coronary vascular smooth muscle due to reduced nitric oxide bioavailability caused by a defect in the endothelial nitric oxide synthethase enzyme which leads to endothelial function abnormalities.
Acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
is normally released by the parasympathetic nervous system
Parasympathetic nervous system
The parasympathetic nervous system is one of the two main divisions of the autonomic nervous system . The ANS is responsible for regulation of internal organs and glands, which occurs unconsciously...
(PSNS) at rest, and causes dilation of the coronary arteries. While acetylcholine induces vasoconstriction of vascular smooth muscle cells through a direct mechanism, acetylcholine also stimulates endothelial cells to produce nitric oxide
Nitric oxide
Nitric oxide, also known as nitrogen monoxide, is a diatomic molecule with chemical formula NO. It is a free radical and is an important intermediate in the chemical industry...
(NO). NO then diffuses out of the endothelial cells, stimulating relaxation of the nearby smooth muscle cells. In healthy arterial walls, the overall indirect relaxation induced by acetylcholine (via nitric oxide) is of greater effect than any contraction that is induced.
When the endothelium is dysfunctional, stimulation with acetylcholine will fail to produce, or produce very little, nitric oxide. Thus, acetylcholine released by the PSNS at rest will simply cause contraction of the vascular smooth muscle. It is potentially by this mechanism that Prinzmetal's angina occurs.
Thromboxane
Thromboxane
Thromboxane is a member of the family of lipids known as eicosanoids. The two major thromboxanes are thromboxane A2 and thromboxane B2. The distinguishing feature of thromboxanes is a 6-membered ether-containing ring....
, a vasoconstrictor with a role in platelet aggregation, may also play a role in Prinzmetal's angina. Lipoprotein(a) interferes with fibrinolysis by competing with plasminogen. The impaired fibrinolysis triggers thrombus formation, which also results in coronary vasospasm in variant angina.
Diagnosis
Although Prinzmetal's Angina has been documented in between 2% to 10% of angina patients, it can be overlooked by cardiologists who stop testing protocol after ruling out typical angina. Patients who develop cardiac chest pain are generally treated empirically as an "acute coronary syndrome", and are generally tested for cardiac enzymes such as creatine kinaseCreatine kinase
Creatine kinase , also known as creatine phosphokinase or phospho-creatine kinase , is an enzyme expressed by various tissues and cell types. CK catalyses the conversion of creatine and consumes adenosine triphosphate to create phosphocreatine and adenosine diphosphate...
isoenzymes or troponin
Troponin
400px|thumb|right|alt = Colored dice with checkered background|Ribbon representation of the human cardiac troponin core complex in the calcium-saturated form...
I or T. These may or may not show a degree of positivity, as coronary spasm too can cause myocardial damage or may leave the arteries undamaged. Echocardiography
Echocardiography
An echocardiogram, often referred to in the medical community as a cardiac ECHO or simply an ECHO, is a sonogram of the heart . Also known as a cardiac ultrasound, it uses standard ultrasound techniques to image two-dimensional slices of the heart...
or thallium scintigraphy is often performed.
The gold standard
Gold standard (test)
In medicine and statistics, gold standard test refers to a diagnostic test or benchmark that is the best available under reasonable conditions. It does not have to be necessarily the best possible test for the condition in absolute terms...
is coronary angiography with injection of provocative agents into the coronary artery. Rarely, an active spasm can be documented angiographically (e.g. if the patient receives an angiogram with intent of performing a primary coronary intervention with angioplasty
Angioplasty
Angioplasty is the technique of mechanically widening a narrowed or obstructed blood vessel, the latter typically being a result of atherosclerosis. An empty and collapsed balloon on a guide wire, known as a balloon catheter, is passed into the narrowed locations and then inflated to a fixed size...
). Depending on the local protocol, provocation testing may involve substances such as ergonovine
Ergonovine
Ergometrine , is an ergoline derivative, and one of the primary ergot and morning glory alkaloids...
, methylergonovine
Methylergonovine
Methylergometrine is a synthetic analogue of ergonovine, a psychedelic alkaloid found in ergot, and many species of morning glory. It is a member of the ergoline family and chemically similar to LSD, ergine, ergometrine, and lysergic acid...
or acetylcholine
Acetylcholine
The chemical compound acetylcholine is a neurotransmitter in both the peripheral nervous system and central nervous system in many organisms including humans...
. Exaggerated spasm is diagnostic of Prinzmetal angina.
ECG finding will more often show ST segment
ST segment
In electrocardiography, the ST segment connects the QRS complex and the T wave and has a duration of 0.08 to 0.12 sec .It starts at the J point and ends at the beginning of the T wave...
elevation than ST depression. Elevation ST-segment in II, III and aVf.
Treatment
Prinzmetal's angina typically responds to nitrateNitrate
The nitrate ion is a polyatomic ion with the molecular formula NO and a molecular mass of 62.0049 g/mol. It is the conjugate base of nitric acid, consisting of one central nitrogen atom surrounded by three identically-bonded oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a...
s and calcium channel blocker
Calcium channel blocker
A calcium channel blocker is a chemical that disrupts the movement of calcium through calcium channels.CCB drugs devised to target neurons are used as antiepileptics. However, the most widespread clinical usage of calcium channel blockers is to decrease blood pressure in patients with...
s.
External links
- www.prinzmetal.dk A site about Prinzmetal variant angina and cardiac syndrome x
- APAA - American Prinzmetal's Angina Association A site that gathers and shows both information for the public and also technical information for medical practitioners.