Editing Angina (section)

==Classification==

===Stable angina<!--stable angina redirects here-->===
Also known as 'effort angina', this refers to the classic type of angina related to [[myocardial ischemia]]. A typical presentation 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 or after administration of [[Sublingual administration|sublingual]] [[nitroglycerin (medication)|nitroglycerin]].<ref name="Stable"/> Symptoms typically diminish several minutes after activity and recur when activity resumes. In this way, stable angina may be thought of as being similar to intermittent [[claudication]] symptoms. Other recognized precipitants of stable angina include cold weather, heavy meals, and [[anxiety|emotional stress]].

===Unstable angina===
{{main|Unstable angina}}
{{See also|Variant angina}}

[[Unstable angina]] (UA) (also "''crescendo angina''"; this is a form of [[acute coronary syndrome]]) is defined as angina pectoris that changes or worsens or begins suddenly at rest.<ref name="urlMerckMedicus : Dorlands Medical Dictionary">{{cite web |url=http://merckmedicus.com/pp/us/hcp/thcp_dorlands_content_split.jsp?pg=/ppdocs/us/common/dorlands/drlnd/one_04/000004949.htm#000004949 |title=MerckMedicus: Dorland's Medical Dictionary |access-date=2009-01-09}}</ref> Unstable angina is a medical emergency and requires urgent medical treatment from a doctor.<ref name=":0" />

It has at least one of these three features:<ref>{{Cite web |title=Unstable Angina |url=https://www.heart.org/en/health-topics/heart-attack/angina-chest-pain/unstable-angina |access-date=2023-10-23 |website=www.heart.org |language=en}}</ref>
# it occurs at rest (or with minimal exertion), usually lasting more than 10 minutes
# it is severe and of new-onset (i.e., within the prior 4–6 weeks)
# it occurs with a [[wikt:crescendo|crescendo]] pattern (i.e., distinctly more severe, prolonged, or frequent than before).

UA may occur often unpredictably and even at rest, which may be a serious indicator of an impending heart attack. The primary factor differentiating unstable angina from stable angina (other than symptoms) is the underlying [[pathophysiology]] of the [[atherosclerosis]]. The pathophysiology of unstable angina is the reduction of coronary blood flow due to transient [[platelet aggregation]] on apparently normal [[endothelium]], coronary artery spasms, or [[coronary thrombosis]].<ref>{{cite journal | vauthors = Hombach V, Höher M, Kochs M, Eggeling T, Schmidt A, Höpp HW, Hilger HH | title = Pathophysiology of unstable angina pectoris--correlations with coronary angioscopic imaging | journal = European Heart Journal | volume = 9 Suppl N | pages = 40–5 | date = December 1988 | pmid = 3246255 | doi = 10.1093/eurheartj/9.suppl_N.40 }}</ref><ref name="Simons2000">{{cite web| vauthors = Simons M |title=Pathophysiology of unstable angina |date=March 8, 2000 |url=http://cmbi.bjmu.edu.cn/uptodate/coronary%20heart%20disease/Pathophysiology/Pathophysiology%20of%20unstable%20angina.htm |access-date=April 28, 2010 |url-status = dead|archive-url=https://web.archive.org/web/20100330044046/http://cmbi.bjmu.edu.cn/uptodate/coronary%20heart%20disease/Pathophysiology/Pathophysiology%20of%20unstable%20angina.htm |archive-date=March 30, 2010 }}</ref>

The process starts with atherosclerosis, progresses through inflammation to yield an active unstable plaque, which undergoes thrombosis and results in acute myocardial ischemia, which, if not reversed, results in cell necrosis (infarction).<ref name="Simons2000" /> Studies show that 64% of all unstable anginas occur between 22:00 and 08:00 when patients are at rest.<ref name="Simons2000" /><ref name="nhlbi">{{cite web |publisher=National Heart Lung and Blood Institute |title=What Is Angina? |access-date=April 28, 2010 |url=http://www.nhlbi.nih.gov/health/dci/Diseases/Angina/Angina_SignsAndSymptoms.html}}</ref>

In stable angina, the developing [[atheroma]] (a fatty plaque) is protected with a [[fibrous cap]]. This cap may rupture in unstable angina, allowing [[blood clots]] to precipitate and further decrease the area of the coronary vessel's [[Lumen (anatomy)|lumen]]  or the interior open space within an artery. This explains why, in many cases, unstable angina develops independently of activity.<ref name="Simons2000" />

===Microvascular angina===

{{main|Microvascular angina}}

[[Microvascular angina]], also known as ''cardiac syndrome X'', is characterized by angina-like chest pain, in the context of normal epicardial coronary arteries (the largest vessels on the surface of the heart, prior to significant branching) on [[angiography]]. The original definition of cardiac syndrome X also mandated that ischemic changes on exercise (despite normal coronary arteries) were displayed, as shown on [[cardiac stress test]]s.<ref>{{cite book| veditors = Kaski JC |title=Chest pain with normal coronary angiograms: pathogenesis, diagnosis and management| date=1999| publisher=Kluwer| location=Boston| isbn=978-0-7923-8421-2| pages=5–6}}</ref> The primary cause of microvascular angina is unknown, but factors apparently involved are endothelial dysfunction and reduced flow (perhaps due to spasm) in the tiny "resistance" blood vessels of the heart.<ref>Guyton, Arthur. "Textbook of Medical Physiology" 11th edition. Philadelphia; Elsevier, 2006.{{page needed|date=February 2013}}</ref> Since microvascular angina is not characterized by major arterial blockages, it is harder to recognize and diagnose.<ref name="HeartHealthyWomen.org">{{cite web
 |title=Cardiac Syndrome X |date=14 August 2022 |publisher=HeartHealthyWomen.org |url=http://www.hearthealthywomen.org/cardiovascular-disease/cardiac-syndrome-x/cardiac-syndrome-x.html}}{{MEDRS|date=February 2013}}</ref><ref>{{cite web| url=http://www.americanheart.org/presenter.jhtml?identifier=4591 |title=Heart Attack and Angina Statistics. |access-date=2010-04-13 |url-status = dead|archive-url=https://web.archive.org/web/20100413012434/http://www.americanheart.org/presenter.jhtml?identifier=4591 |archive-date=2010-04-13 }} {{failed verification|date=March 2013}}.</ref><ref>
{{cite web |title=Angina |publisher=Texas Heart Institute |date=October 2012 |url=http://www.texasheartinstitute.org/hic/topics/cond/angina.cfm |access-date=2010-05-04 |archive-url=https://web.archive.org/web/20140817121322/http://www.texasheartinstitute.org/HIC/Topics/Cond/Angina.cfm |archive-date=2014-08-17 |url-status = dead}}
</ref>

Microvascular angina was previously considered a rather benign condition, but more recent data has changed this attitude. Studies, including the Women's Ischemia Syndrome Evaluation (WISE), suggest that microvascular angina is part of the pathophysiology of ischemic heart disease, perhaps explaining the higher rates of angina in females than in males, as well as their predilection towards [[ischemia]] and acute coronary syndromes in the absence of obstructive coronary artery disease.<ref>{{cite journal | vauthors = Gulati M, Shaw LJ, Bairey Merz CN | title = Myocardial ischemia in women: lessons from the NHLBI WISE study | journal = Clinical Cardiology | volume = 35 | issue = 3 | pages = 141–8 | date = March 2012 | pmid = 22389117 | pmc = 3297966 | doi = 10.1002/clc.21966 }}</ref>