T wave

T-waveTT wavesT-waves
In electrocardiography, the T wave represents the repolarization of the ventricles.wikipedia
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Electrocardiography

electrocardiogramECGEKG
In electrocardiography, the T wave represents the repolarization of the ventricles.
There are three main components to an ECG: the P wave, which represents the depolarization of the atria; the QRS complex, which represents the depolarization of the ventricles; and the T wave, which represents the repolarization of the ventricles.

T wave alternans

T-wave alternans
A periodic beat-to-beat variation in the amplitude or shape of the T wave may be termed T wave alternans.
T wave alternans (TWA) is a periodic beat-to-beat variation in the amplitude or shape of the T wave in an electrocardiogram (ECG or EKG)

QRS complex

QRSJ-pointR wave
The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period.
The T wave follows the S wave, and in some cases, an additional U wave follows the T wave.

ST segment

Both the abnormalities of the ST segment and T wave represents the abnormalities of the ventricular repolarization or secondary to abnormalities in ventricular depolarisation.
In electrocardiography, the ST segment connects the QRS complex and the T wave and has a duration of 0.005 to 0.150 sec (5 to 150 ms).

Repolarization

repolarizingrepolarizerepolarisation
In electrocardiography, the T wave represents the repolarization of the ventricles.
In the human ventricles, repolarization can be seen on an ECG (Electrocardiogram) via the J-wave (Osborn), ST segment, T wave and U wave.

Wellens' syndrome

Wellens' sign or warning
Wellens' syndrome is caused by the injury or blockage of the left anterior descending artery, therefore resulting in symmetrical T wave inversions from V2 to V4 with depth more than 5 mm in 75% of the cases.
Originally thought of as two separate presentations, A and B, it is now considered an evolving wave form, initially of biphasic T wave inversions and later becoming symmetrical, often deep (>2 mm), T wave inversions in the anterior precordial leads.

U wave

U wavesU-Wave
Hypokalemia or digitalis therapy can cause flattened T wave with a prominent U wave.
Higher values of heart rate or hypocalcemia U wave are superimposed on the T wave and in tachycardia — merges with the R-wave of the next cardiac cycle.

Pulmonary embolism

pulmonary embolipulmonary emboluspulmonary thrombosis
In pulmonary embolism, T wave can be symmetrically inverted at V1 to V4 leads but sinus tachycardia is usually the more common finding.
An ECG may show signs of right heart strain or acute cor pulmonale in cases of large PEs — the classic signs are a large S wave in lead I, a large Q wave in lead III, and an inverted T wave in lead III (S1Q3T3), which occurs in 12–50% of people with the diagnosis, yet also occurs in 12% without the diagnosis.

Sinus tachycardia

High heart ratetachycardia, sinus
In pulmonary embolism, T wave can be symmetrically inverted at V1 to V4 leads but sinus tachycardia is usually the more common finding.

Myocardial infarction

heart attackheart attacksacute myocardial infarction
Additionally, patients exhibiting the early stages of STEMI may display these broad and disproportional waves.
In addition to a rise in biomarkers, a rise in the ST segment, changes in the shape or flipping of T waves, new Q waves, or a new left bundle branch block can be used to diagnose an AMI.

Hypokalemia

hypokalaemialow blood potassiumhypokalemic
Hypokalemia or digitalis therapy can cause flattened T wave with a prominent U wave.

Refractory period (physiology)

refractory periodrefractorinessrefractory periods
The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period.

QT interval

QTcQTc intervalCorrected QT interval
The T wave contains more information than the QT interval.

Action potential

action potentialsnerve impulsenerve impulses
Nerves that innervate skeletal muscle have an extremely short refractory period after being subjected to an action potential (1 ms).

Tetanic contraction

tetanictetanizedtetanic force
This can lead to sustained or tetanic contraction.

Cardiac action potential

action potentialphase 1 of the cardiac action potentialautomaticity
This prevents the heart from undergoing sustained contractions because it forces the refractory period and cardiac action potential firing to be of the same length of time.

Sodium

NaNa + sodium ion
Sodium ions flowed into the cell earlier to depolarize it and cause skeletal muscle contraction.

Potassium

KK + potassium ion
Once the action potential is over, potassium ions flow out of the cell due to increased cell membrane permeability to those ions.

Cell membrane

plasma membranemembranecell membranes
Once the action potential is over, potassium ions flow out of the cell due to increased cell membrane permeability to those ions.

Membrane potential

transmembrane potentialcell potentialcell-potential
This high permeability contributes to the rapid repolarization of the membrane potential.

Chest pain

chest painschest tightnesschest
Inverted T waves associated with cardiac signs and symptoms (chest pain and cardiac murmur) are highly suggestive of myocardial ischaemia.

Heart murmur

heart murmursmurmurmurmurs
Inverted T waves associated with cardiac signs and symptoms (chest pain and cardiac murmur) are highly suggestive of myocardial ischaemia.

Coronary artery disease

coronary heart diseaseischemic heart diseaseischaemic heart disease
Inverted T waves associated with cardiac signs and symptoms (chest pain and cardiac murmur) are highly suggestive of myocardial ischaemia.

Left anterior descending artery

anterior interventricularleft anterior descendingAnterior interventricular branch of left coronary artery
Wellens' syndrome is caused by the injury or blockage of the left anterior descending artery, therefore resulting in symmetrical T wave inversions from V2 to V4 with depth more than 5 mm in 75% of the cases.