Editing Cardiology (section)

===Cardiac arrhythmia===
{{Main|Arrhythmia}}

Cardiac arrhythmia, also known as "cardiac dysrhythmia" or "irregular heartbeat", is a group of conditions in which the [[Cardiac cycle|heartbeat]] is too fast, too slow, or irregular in its rhythm.<!-- <ref name=NIH2011Def/> --> A [[heart rate]] that is too fast – above 100 beats per minute in adults – is called [[tachycardia]]. A heart rate that is too slow – below 60 beats per minute – is called [[bradycardia]].<ref name="NIH2011Def">{{cite web|title=What Is Arrhythmia?|url=http://www.nhlbi.nih.gov/health/health-topics/topics/arr|website=www.nhlbi.nih.gov|access-date=7 March 2015|date=July 1, 2011|archive-url=https://web.archive.org/web/20150302074103/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/|archive-date=2 March 2015|url-status=dead}}</ref> Many types of arrhythmia present no symptoms.<!-- <ref name=NIH2011Sym-a/> --> When symptoms are present, they may include [[palpitations]], or feeling a pause between heartbeats.<!-- <ref name=NIH2011Sym-a/> --> More serious symptoms may include [[presyncope|lightheadedness]], [[Syncope (medicine)|passing out]], [[shortness of breath]], or [[chest pain]].<ref name="NIH2011Sym-a">{{cite web|title=What Are the Signs and Symptoms of an Arrhythmia?|url=http://www.nhlbi.nih.gov/health/health-topics/topics/arr/signs|website=www.nhlbi.nih.gov|access-date=7 March 2015|date=July 1, 2011|archive-url=https://web.archive.org/web/20150219081446/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/signs|archive-date=19 February 2015|url-status=dead}}</ref> While most types of arrhythmia are not serious, some predispose a person to complications such as [[stroke]] or [[heart failure]].<ref name="NIH2011Def" /><ref name="NIH2011Type" /> Others may result in [[cardiac arrest]].<ref name="NIH2011Type" />

<!-- Cause and diagnosis -->
There are four main types of arrhythmia: [[premature heart beat|extra beats]], [[supraventricular tachycardia]]s, [[ventricular arrhythmia]]s, and [[bradyarrhythmia]]s.<!-- <ref name=NIH2011Type/> --> Extra beats include [[premature atrial contraction]]s, [[premature ventricular contraction]]s, and [[premature junctional contractions]].<!-- <ref name=NIH2011Type/> --> Supraventricular tachycardias include [[atrial fibrillation]], [[atrial flutter]], and [[paroxysmal supraventricular tachycardia]].<!-- <ref name=NIH2011Type/> --> Ventricular arrhythmias include [[ventricular fibrillation]] and [[ventricular tachycardia]].<ref name="NIH2011Type">{{cite web|title=Types of Arrhythmia|url=http://www.nhlbi.nih.gov/health/health-topics/topics/arr/types|website=www.nhlbi.nih.gov|access-date=7 March 2015|date=July 1, 2011|archive-url=https://web.archive.org/web/20150607165144/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/types|archive-date=7 June 2015|url-status=dead}}</ref><ref name="Martin2012">{{cite journal|last1=Martin|first1=C|last2=Matthews|first2=G|last3=Huang|first3=CL|title=Sudden cardiac death and Inherited channelopathy: the basic electrophysiology of the myocyte and myocardium in ion channel disease|journal=Heart|date=2012|volume=98|issue=7|pages=536–543|pmid=22422742|doi=10.1136/heartjnl-2011-300953|pmc=3308472}}</ref> Arrhythmias are due to problems with the [[electrical conduction system of the heart]].<ref name="NIH2011Def" /> Arrhythmias may occur in children; however, the normal range for the heart rate is different and depends on age.<ref name="NIH2011Type" /> A number of tests can help diagnose arrhythmia, including an electrocardiogram and [[Holter monitor]].<ref>{{cite web|title=How Are Arrhythmias Diagnosed?|url=http://www.nhlbi.nih.gov/health/health-topics/topics/arr/diagnosis|website=www.nhlbi.nih.gov/|access-date=7 March 2015|date=July 1, 2011|archive-url=https://web.archive.org/web/20150218075708/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/diagnosis|archive-date=18 February 2015|url-status=dead}}</ref>

<!-- Treatment -->
Most arrhythmias can be effectively treated.<ref name=NIH2011Def/> Treatments may include medications, medical procedures such as a [[pacemaker]], and surgery.<!-- <ref name=NIH2011Tx-Arrhythmias/> --> Medications for a fast heart rate may include [[beta blockers]] or [[antiarrhythmic agent|agents that attempt to restore a normal heart rhythm]] such as [[procainamide]].<!-- <ref name=NIH2011Tx-Arrhythmias/> --> This later group may have more significant side effects especially if taken for a long period of time.<!-- <ref name=NIH2011Tx-Arrhythmias/> --> Pacemakers are often used for slow heart rates.<!-- <ref name=NIH2011Tx-Arrhythmias/> --> Those with an irregular heartbeat are often treated with [[blood thinner]]s to reduce the risk of complications.<!-- <ref name=NIH2011Tx-Arrhythmias/> --> Those who have severe symptoms from an arrhythmia may receive urgent treatment with a jolt of electricity in the form of [[cardioversion]] or [[defibrillation]].<ref name=NIH2011Tx-Arrhythmias>{{cite web|title=How Are Arrhythmias Treated?|url=http://www.nhlbi.nih.gov/health/health-topics/topics/arr/treatment|website=www.nhlbi.nih.gov/|access-date=7 March 2015|date=July 1, 2011|archive-url=https://web.archive.org/web/20150217135319/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/treatment|archive-date=17 February 2015|url-status=dead}}</ref>

<!-- Epidemiology -->
Arrhythmia affects millions of people.<ref name=NIH2011Risk>{{cite web|title=Who Is at Risk for an Arrhythmia?|url=http://www.nhlbi.nih.gov/health/health-topics/topics/arr/atrisk|website=www.nhlbi.nih.gov/|access-date=7 March 2015|date=July 1, 2011|archive-url=https://web.archive.org/web/20150303190136/http://www.nhlbi.nih.gov/health/health-topics/topics/arr/atrisk|archive-date=3 March 2015|url-status=dead}}</ref> In Europe and North America, as of 2014, atrial fibrillation affects about 2% to 3% of the population.<ref name=Zoni2014>{{cite journal|last1=Zoni-Berisso|first1=M|last2=Lercari|first2=F|last3=Carazza|first3=T|last4=Domenicucci|first4=S|title=Epidemiology of atrial fibrillation: European perspective|journal=Clinical Epidemiology|date=2014|volume=6|pages=213–20|pmid=24966695|doi=10.2147/CLEP.S47385|pmc=4064952|doi-access=free}}</ref> Atrial fibrillation and atrial flutter resulted in 112,000 deaths in 2013, up from 29,000 in 1990.<ref name="pmid25530442"/> [[Sudden cardiac death]] is the cause of about half of deaths due to cardiovascular disease or about 15% of all deaths globally.<ref name=Meh2007>{{cite journal|last1=Mehra|first1=R|title=Global public health problem of sudden cardiac death|journal=[[Journal of Electrocardiology]]|date=2007|volume=40|issue=6 Suppl|pages=S118–22|pmid=17993308|doi=10.1016/j.jelectrocard.2007.06.023}}</ref> About 80% of sudden cardiac death is the result of ventricular arrhythmias.<ref name=Meh2007/> Arrhythmias may occur at any age but are more common among older people.<ref name=NIH2011Risk/>