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T Wave

T wave

Repolarization and ECG

Propagation of the Repolarization Wave and ECG

• The repolarization wave (extracellular change from - to +) propagates in the myocardial wall from the epicardium to the endocardium
• Because the epicardium starts to repolarize earlier
• The wave has the opposite direction compared to depolarization
• However, the electrical vector always points from the (-) to the (+) part of the myocardium
• The electrical vector has the same direction during both depolarization and repolarization
• The repolarization wave propagates slowly
• Because the calcium and potassium channels open slowly at the end of the action potential in cardiomyocytes
• The repolarization wave moves away from the ECG electrode, but the electrical vector points towards the ECG electrode
• Repolarization occurs slowly, resulting in a wide T wave
• The width of the T wave is the time it takes to repolarize the ventricles

Depolarization and Repolarization in the Ventricles

Action Potential in the Endocardium and Epicardium

• The action potential of cardiomyocytes in the endocardium and epicardium has different electrical properties
• The conduction system activates the myocardium in the endocardium
• Thus, depolarization begins in the endocardium
• Depolarization in the endocardium and epicardium is nearly synchronous
• Therefore, the depolarization wave travels rapidly through the myocardial wall
• Cardiomyocytes in the epicardium begin to repolarize earlier than those in the endocardium
• Therefore, the repolarization wave starts in the epicardium
  
  
• However, the electrical vector of depolarization and repolarization points in the same direction

T Wave (Most Variable Wave)

• It is the most variable wave on the ECG
• It represents ventricular repolarization
• It is low and wide
• Repolarization (T wave) is more asynchronous than depolarization (QRS complex)

High Peaked T Wave

• It is tall, sometimes taller than the R wave
• In hyperkalemia, it is symmetrical (resembling the Eiffel Tower)
• In hyperacute ischemia, it has a broad base and is not symmetrical
• It is referred to as a hyperacute T wave

• Hyperkalemia (V1-V6, T wave resembling the Eiffel Tower)
• Hyperacute STEMI infarction (at least in 2 adjacent leads, ischemia dynamics)
• Prinzmetal's angina pectoris (at least in 2 adjacent leads)
  
  

Inverted T Wave

• Concordant inverted T wave is not pathological
• In lead III, it may be discordantly inverted
• Pathological inverted T wave is
• Inverted T wave > 3mm or newly appeared

• Normal variant in children (V1-V3)
• Persistent juvenile T waves (in adults V1-V3)
• Athletes (V1-V3)
• Myocardial ischemia (at least in 2 adjacent leads)
• Subendocardial ischemia, post-acute STEMI
• Hyperventilation (V1-V5)
• Left bundle branch block (I, aVL, V5-V6)
• Right bundle branch block (V1-V3)
• Left ventricular hypertrophy (I, aVL, V5-V6)
• Right ventricular hypertrophy (V1-V3) (II, III, aVF)
• Pulmonary embolism (V1-V3) (II, III, aVF)
• Arrhythmogenic right ventricular dysplasia (V1-V3)
• Hypertrophic cardiomyopathy (V1-V6)
• Intracranial hypertension (V1-V6) (II, III, aVF)
• Wellens syndrome (Type I: V2-V3)
• WPW syndrome: Type A: (V1-V3), Type B: (V4-V6)
• Hypothyroidism (V1-V6)
• Pacemaker

Double T Wave

• The T wave has 2 positive amplitudes, with a notch in the middle
• In reality, it is a T wave that is associated with a P wave or a U wave

• Hypokalemia (in all leads, T wave + U wave)
• Sinus tachycardia (in all leads, T wave + P wave)
• AV block I° (in all leads, T wave + P wave)
• AV block II° (2:1) (in all leads)

Normal T Wave

Normal T Wave and Sinus Rhythm

• Normal T Wave
• Is always positive (I, II, V3-V6)
• Is concordant (has the same polarity as QRS complex)
• Is negative (aVR, V1) if the QRS is also negative
• In lead III, it may be discordantly negative
• Amplitude
• Limb leads < 5mm
• Precordial leads < 15mm
• Sinus Rhythm

Tall Peaked T Waves and Hyperkalemia

• Symmetrical peaked T waves (resembling the Eiffel Tower)
• T wave amplitude
• In precordial leads > 5mm
• In chest leads > 15mm
• The patient had hyperkalemia of 7.1mmol/l

High T Waves and Benign Early Repolarization

• High peaked T waves (V2-V6)
• T waves in benign early repolarization do not change—they persist for years
• T waves in STEMI infarction change; the patient should have a different EKG in an hour (STEMI dynamics)
• Benign early repolarization
• Concave ST elevations (V2-V5)
• In leads (V3-V5) there is a fishhook
• This is typical for benign early repolarization

Inverted T Waves - Persistent Juvenile

• Negative T waves in V1-V3
• If these T waves were new, it would indicate ischemia
• Persistent juvenile T waves
• Present from childhood and persist into adulthood (do not change)
• Most common in Afro-Caribbean women
• Usually deep, max. 3mm (though this is not a strict rule)

Inverted Ischemic T Waves and Unstable Angina Pectoris

• The patient had unstable angina pectoris due to stenosis of the RIA and RCx
• ST depression (V4-V6)
• Inverted T waves (V2-V6)
• After stent placement (recanalization), T waves later normalized
• Acute subendocardial ischemia is characterized by
• ST depression and inverted T waves (in at least 2 adjacent leads)

Inverted T Waves and Left Tawar Branch Block

• Left Tawar Branch Block has
• Wide QRS complex (>0.12s)
• Negative T waves in lateral leads (I, aVL, V5, V6)
• Deep S waves (V1), dominant R waves (V6)

Inverted T Waves and Left Ventricular Hypertrophy

• Left Ventricular Hypertrophy
• QRS complexes are narrow (< 0.12s)
• Positive Sokolow index: R(V5) + S(V1) > 35mm
• In left ventricular hypertrophy, left ventricular overload occurs:
• Negative T waves in lateral leads (I, aVL, V5-6)
• Descending ST depressions (I, aVL, V5-6)

Inverted T Waves and Pulmonary Embolism

• In acute pulmonary embolism, right ventricular overload occurs
• Negative T waves in (V1-V3, III)
• S1Q3T3
• S(I), Q(III), negative T (III)
• Is a typical EKG sign of embolism

Inverted T Waves and Hypertrophic Cardiomyopathy

• Left Ventricular Hypertrophy
• R(V5) + S(V1) > 35mm
• Right Ventricular Hypertrophy
• R(V1) > 7mm
• Hypertrophic Cardiomyopathy causes
• Negative T waves (V1-V6), sometimes also in limb leads

Inverted T Waves and Wellens Syndrome (Type I)

• Wellens Syndrome (Type I)
• Creates deep T waves (V2-V3) (rarely V1-V6)
• Type II is more common, producing negative bifasic T waves (the terminal part of the T wave is negative)

Inverted T Waves and WPW Syndrome (Type B)

• WPW Syndrome Type B
• Delta wave and a widened QRS of approximately 0.15s
• Shortened PQ interval < 0.12s
• Negative QRS (V1)
• This indicates that the Kent bundle is located in the right atrium
• Negative T waves (V5-V6, II, III, aVF)

Inverted T Waves and Pacemaker

• This concerns pacing of both atria and ventricles
• Stimulus artifacts are observed before the P wave and before the QRS
• The ventricles are stimulated from the right ventricle (the electrode is in the right ventricle)
• This creates a pattern resembling left bundle branch block
• Wide QRS complex (>0.12s)
• Negative T waves in the lateral leads (I, aVL, V5, V6)
• Deep S (V1), dominant R (V6)

Biphasic Negative T Waves and Wellens' Syndrome (Type II)

• Wellens' Syndrome (Type II)
• It creates biphasic negative T waves (V2-V3) (rarely V1-V6)
• It is more common than Type I

Double T Wave

• The T wave has 2 positive amplitudes and a notch in the middle
• In reality, this is a T wave that is combined with a P wave or a U wave

Double T Wave and Hypokalemia

• In hypokalemia, a U wave occurs
• Double T wave
• A U wave follows closely after the T wave (T + U wave)

Double T Wave and First-Degree AV Block

• In first-degree AV block
• There is a prolonged PQ interval (>0.2s)
• The QRS-T complex occurs later
• The T wave thus moves closer to the P wave
• Double T wave
• A P wave follows closely after the T wave (T + P wave)

Flattened T Wave

• Concordant flattened T wave is a non-specific change on the ECG
• It rarely occurs with certain diagnoses

Ischemia and Flattened T Waves

• Subendocardial ischemia
• Creates Inverted T waves
• Rarely flattened T waves
• At least in 2 adjacent leads
• On the ECG, flattened T waves (V1-V6)
• ECG is dynamic during ischemia

Sinus Rhythm and Normal T Waves

• This is an ECG from the patient on the left
• The patient stopped bicycling on the ergometer
• After the cessation of exertion (ischemia), the ECG normalized
• The ECG shows a sinus rhythm

Flattened T Waves and Severe Hypothyroidism

• In severe hypothyroidism, myxedema triad: occurs
• Sinus bradycardia (30/min.)
• Low QRS voltage, mainly in limb leads (I, II, III, aVF, aVL, aVR)
• Wide negative T waves (V1-V6)
• Sometimes the T waves are flattened