Editing Electrocardiography (section)

===Ischemia and infarction===
{{Main|Electrocardiography in myocardial infarction}}
Ischemia or [[NSTEMI|non-ST elevation myocardial infarctions]] (non-STEMIs) may manifest as [[ST depression]] or inversion of [[T wave]]s. It may also affect the [[HFQRS|high frequency band of the QRS]].

[[STEMI|ST elevation myocardial infarctions]] (STEMIs) have different characteristic ECG findings based on the amount of time elapsed since the MI first occurred. The earliest sign is ''hyperacute T waves,'' peaked T waves due to local [[hyperkalemia]] in ischemic myocardium. This then progresses over a period of minutes to elevations of the [[ST segment]] by at least 1&nbsp;mm. Over a period of hours, a pathologic [[QRS complex#Q wave|Q wave]] may appear and the T wave will invert. Over a period of days the ST elevation will resolve. Pathologic Q waves generally will remain permanently.<ref name="Alpert-2000">{{Cite journal |vauthors=Alpert JS, Thygesen K, Antman E, Bassand JP |year=2000 |title=Myocardial infarction redefined – a consensus document of The Joint European Society of Cardiology/American College of Cardiology Committee for the redefinition of myocardial infarction |journal=J Am Coll Cardiol |volume=36 |issue=3 |pages=959–969 |doi=10.1016/S0735-1097(00)00804-4 |pmid=10987628|doi-access=free }}</ref>

The [[coronary artery]] that has been occluded can be identified in an STEMI based on the location of ST elevation. The [[Anterior interventricular branch of left coronary artery|left anterior descending]] (LAD) artery supplies the anterior wall of the heart, and therefore causes ST elevations in anterior leads (V<sub>1</sub> and V<sub>2</sub>). The [[Circumflex branch of left coronary artery|LCx]] supplies the lateral aspect of the heart and therefore causes ST elevations in lateral leads (I, aVL and V<sub>6</sub>). The [[right coronary artery]] (RCA) usually supplies the inferior aspect of the heart, and therefore causes ST elevations in inferior leads (II, III and aVF).<ref>{{Citation |last1=Warner |first1=Matthew J. |title=Inferior Myocardial Infarction |date=2022 |url=http://www.ncbi.nlm.nih.gov/books/NBK470572/ |work=StatPearls |place=Treasure Island (FL) |publisher=StatPearls Publishing |pmid=29262146 |access-date=2022-10-28 |last2=Tivakaran |first2=Vijai S.}}</ref>