• Mechanism of U Wave Formation
• ECG and U Wave
• Prominent U Wave
• Inverted U Wave
• Inverted U Wave

Mechanism of U Wave Formation

• The mechanism is questionable, it is assumed:
• Delayed repolarization of the ventricular septum
• Delayed repolarization of certain parts of the ventricles
• Repolarization of the Purkinje fibers

Prominent U Wave

• Amplitude is
• > 1-2mm
• or > 25% of the T wave
• Causes of a prominent U wave
• almost always prolong the QT interval
  
  
• Most common causes:
• Bradycardia
• Hypokalemia
• Less common causes
• Hypocalcemia
• Hypomagnesemia
• Hypothermia
• Increased intracranial pressure
• Left ventricular hypertrophy
• Hypertrophic cardiomyopathy
• Digoxin
• Antiarrhythmics

Normal U Wave and Sinus Bradycardia

• Sinus Bradycardia
• Heart Rate 33/min.
• U Wave (aVR, V2, V4-6)
• This is not a typical prominent U wave (over 2mm) seen in bradycardia
• In this case, the U wave is physiological
• This concerns a patient with anorexia and sinus bradycardia

U Wave and Hypocalcemia

• U waves (V2-V3)
• Not a typical prominent U wave (above 2mm)
• Prolonged QT interval (QT_c 0.5s)

U Wave and Hypothermia

• Hypothermia causes sinus bradycardia
• Sinus bradycardia
• Heart rate 30/min.
• U waves (V2-V6)
• Not a typical prominent U wave (over 2mm)
• The patient was hypothermic (36°C)

U Wave and Left Ventricular Hypertrophy

• U wave (aVL, V2-V3)
• Left Ventricular Hypertrophy
• Huge S and R waves in precordial leads that extend into adjacent leads
• Positive Sokolow index
• S(V1/2) + R(V5/6) ≥ 35mm
• Left Ventricular Overload
• Descending ST depressions in lateral leads (V5-V6, I)

U Wave and Digoxin

• Prominent U waves with the use of digoxin (V2-V6)
• Not indicative of digoxin overdose

Unstable Angina Pectoris

• The patient experienced chest pain
• Troponin was normal (a marker for myocardial infarction)
• Inverted U Waves (arrows)
• The U wave is often the first marker of myocardial ischemia

Prinzmetal's Angina

• Inverted U Waves
• Prinzmetal's angina
• It is a spasm of the coronary artery
• Large ST elevations (STEMI picture)
• Resolves in about 30 minutes
• No myocardial necrosis occurs
• Troponin is normal