Editing T wave (section)

{{Short description|Electrocardiogram waveform representing repolarization of the heart's ventricles}}
{{for|the electromagnetic waves sometimes referred to as T-waves|Terahertz radiation}}
[[Image:Tnorm_(ECG).svg|right|thumb|Normal T wave]]

In [[electrocardiography]], the '''T wave''' represents the [[repolarization]] of the [[Ventricle (heart)|ventricle]]s. The interval from the beginning of the [[QRS complex]] to the apex of the T wave is referred to as the ''absolute [[refractory period (physiology)|refractory period]]''. The last half of the T wave is referred to as the ''relative refractory period'' or ''vulnerable period''. The T wave contains more information than the [[QT interval]]. The T wave can be described by its symmetry, skewness, slope of ascending and descending limbs, amplitude and subintervals like the T<sub>peak</sub>–T<sub>end</sub> interval.<ref>{{cite journal|title=Reference values of electrocardiogram repolarization variables in a healthy population |year=2010 |vauthors=Haarmark C, Graff C, Andersen MP, etal |journal=[[Journal of Electrocardiology]]|volume=43 |pages=31–39 |issue=1 |pmid=19740481|doi=10.1016/j.jelectrocard.2009.08.001}}</ref>

In most [[Electrocardiography#Electrodes and leads|leads]], the T wave is positive. This is due to the repolarization of the membrane. During ventricle contraction (QRS complex), the heart depolarizes. Repolarization of the ventricle happens in the opposite direction of depolarization and is negative current, signifying the relaxation of the cardiac muscle of the ventricles. But this negative flow causes a positive T wave; although the cell becomes more negatively charged, the net effect is in the positive direction, and the ECG reports this as a positive spike.<ref>{{Cite web|url= http://www.kumc.edu/AMA-MSS/Study/phys2.htm |title= Physiology: Cardiovascular}}</ref> However, a negative T wave is normal in [[lead aVR]]. Lead V1 generally have a negative T wave. In addition, it is not uncommon to have a negative T wave in lead III, aVL, or aVF. A periodic beat-to-beat variation in the amplitude or shape of the T wave may be termed [[T wave alternans]].