Unstable angina

Symptoms of unstable angina are the same as those of stable angina, however the pattern of the symptoms changes.{{Cite web |title=Acute Coronary Syndromes (Heart Attack; Myocardial Infarction; Unstable Angina) - Heart and Blood Vessel Disorders |url=https://www.msdmanuals.com/home/heart-and-blood-vessel-disorders/coronary-artery-disease/acute-coronary-syndromes-heart-attack-myocardial-infarction-unstable-angina |access-date=2023-02-12 |website=MSD Manual Consumer Version |language=en}} In unstable angina, symptoms related to decreased blood flow to the heart may appear on rest or on minimal exertion. The symptoms can last longer than those in stable angina, can be resistant to rest or medicine, and can get worse over time.{{Cite web |publisher=American Heart Association |title=Unstable Angina |url=https://www.heart.org/en/health-topics/heart-attack/angina-chest-pain/unstable-angina |url-status=live |archive-url=https://web.archive.org/web/20230315022035/https://www.heart.org/en/health-topics/heart-attack/angina-chest-pain/unstable-angina |archive-date=2023-03-15 |access-date=2023-05-05 |website=www.heart.org |language=en}}

The cardinal symptom of critically decreased blood flow to the heart is chest pain, experienced as tightness, pressure, or burning. Localisation is most commonly around or over the chest and may radiate or be located to the arm, shoulder, neck, back, upper abdomen, or jaw. This may be associated with sweating, nausea, or shortness of breath. Previously the word "atypical" was used to describe chest pain not typically heart-related; however, this word is recommended against and has been replaced by "noncardiac" to describe chest pain that indicate a low likelihood of heart-related pain.

The pathophysiology of unstable angina is controversial. Previously, unstable angina was assumed to be angina pectoris caused by disruption of an atherosclerotic plaque with partial thrombosis and possibly embolization or vasospasm leading to myocardial ischemia.{{Cite book |last=Robbins |year=2005 |title=Pathologic Basis of Disease |edition=7th}}{{cite journal |last1=Braunwald |first1=E. |year=1998 |title=Unstable Angina: An Etiologic Approach to Management |journal=Circulation |volume=98 |issue=21 |pages=2219–2222 |doi=10.1161/01.CIR.98.21.2219|pmid=9826306 |doi-access=free }} However, sensitive troponin assays reveal rise of cardiac troponin in the bloodstream with episodes of even mild myocardial ischemia.{{Cite journal |last1=Sabatine|first1=M. S.|last2=Morrow|first2=R. W.|last3=de Lemos|first3=J.A.|last4=Jarolim|first4=P.|last5=Braunwald|first5=E.|year=2009 |title=Detection of acute changes in circulating troponin in the setting of transient stress test-induced myocardial ischaemia using an ultrasensitive assay: results from TIMI 35|journal=European Heart Journal |volume=30 |issue=2 |pages=162–169 |doi=10.1093/eurheartj/ehn504|pmid=18997177|pmc=2721709}} Since unstable angina is assumed to occur in the setting of acute myocardial ischemia without troponin release, the concept of unstable angina is being questioned with some calling for retiring the term altogether.{{Cite journal |last1=Braunwald|first1=E.|last2=Morrow|first2=R. W.|year=2013 |title=Unstable Angina. Is It Time for a Requiem?|journal=Circulation |volume=127 |issue=24 |pages=2452–2457 |doi=10.1161/CIRCULATIONAHA.113.001258|pmid=23775194|doi-access=free}}

Unstable angina is characterized by at least one of the following:

1. Occurs at rest or minimal exertion and usually lasts more than 20 minutes (if nitroglycerin is not administered)
2. Being severe (at least Canadian Cardiovascular Society Classification 3) and of new onset (i.e. within 1 month)
3. Occurs with a crescendo pattern (brought on by less activity, more severe, more prolonged or increased frequency than previously).{{cite journal |last1=Robert A. |first1=Chahine |title=Unstable angina The problem of definition |url=https://heart.bmj.com/content/heartjnl/37/12/1246.full.pdf |journal=British Heart Journal|date=1975 |volume=37 |issue=12 |pages=1246–1249 |doi=10.1136/hrt.37.12.1246 |pmid=1225338 |pmc=482947 }}{{cite journal | last= Braunwald |first=E |display-authors=etal | year = 2002 | title = ACC/AHA guideline update for the management of patients with unstable angina and non-ST segment elevation myocardial infarction-2002: Summary Article: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee on the Management of Patients with Unstable Angina)| journal = Circulation | volume = 106 | issue = 14 | pages = 1893–1900 | doi=10.1161/01.cir.0000037106.76139.53|pmid=12356647 | doi-access = free }}Libby: Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine

Fifty percent of people with unstable angina will have evidence of necrosis of the heart's muscular cells based on elevated cardiac serum markers such as creatine kinase isoenzyme (CK)-MB and troponin T or troponin I, and thus have a diagnosis of non-ST elevation myocardial infarction.{{cite journal |last1=Markenvard |first1=J |last2=Dellborg |first2=M |last3=Jagenburg |first3=R |last4=Swedberg |first4=K |title=The predictive value of CKMB mass concentration in unstable angina pectoris: preliminary report |journal=Journal of Internal Medicine |year=1992 |volume=231 |issue=4 |pages=433–6 |doi=10.1111/j.1365-2796.1992.tb00956.x |pmid=1588271|s2cid=32268852 }}

Nitroglycerin can be used immediately to dilate the venous system and reduce the circulating blood volume, therefore reducing the work and oxygen demand of the heart.{{cite journal|last=Murrell |first=William |date=1879 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.d0000772988;view=1up;seq=78 |title=Nitroglycerin as a remedy for angina pectoris |journal=The Lancet |volume=1 |issue=2890 |pages=80–81, 113–115, 151–152, 225–227|doi=10.1016/s0140-6736(02)46032-1 |pmc=5901592 |hdl=2027/uc1.b5295238 |hdl-access=free }}{{cite book|last=Sneader |first=Walter |title=Drug Discovery: A History |publisher=John Wiley and Sons |date=2005 |isbn=978-0-471-89980-8}} In addition, nitroglycerin causes peripheral venous and artery dilation reducing cardiac preload and afterload. These reductions allow for decreased stress on the heart and therefore lower the oxygen demand of the heart's muscle cells.{{cite journal |last1=Boden |first1=William E. |last2=Padala |first2=Santosh K. |last3=Cabral |first3=Katherine P. |last4=Buschmann |first4=Ivo R. |last5=Sindhu |first5=Mandeep S. |year=2015 |title=Role of short-acting nitroglycerin in the management of ischemic heart disease |journal=Drug Design, Development and Therapy |volume= 9|pages=4793–805 |doi=10.2147/DDDT.S79116|pmid=26316714 |pmc=4548722 |doi-access=free }}

Antiplatelet drugs such as aspirin and clopidogrel can reduce platelet aggregation at the unstable atherosclerotic plaque, as well as combining these with an anticoagulant such as a low molecular weight heparin, can reduce clot formation.{{cite journal |last1=Robert |first1=Chahine |title=Unstable angina |url=https://heart.bmj.com/content/heartjnl/37/12/1246.full.pdf |journal=British Heart Journal|date=1975 |volume=37 |issue=12 |pages=1246–1249 |doi=10.1136/hrt.37.12.1246 |pmid=1225338 |pmc=482947 }}

• Variant angina

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{{Medical resources

| DiseasesDB = 13530

| ICD10 = {{ICD10|I|20|0|i|20}}

| ICD9 = {{ICD9|411.1}}

| ICDO =

| OMIM =

| MedlinePlus = 000201

| eMedicineSubj =

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| MeshID = D000789

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{{Heart diseases}}

Category:Ischemic heart diseases