12-Lead Electrocardiographya comprehensive course

Adam Thompson, EMT-P, A.S.

Morphologi

es

(The “T”)

T Wave

• Should not be symmetrical.

• Should be upright in every lead but aVR.

• Height should correlate with QRS.

• Should have a dull peak.

Symmetrical T-Wave

AsymmetricalNormal

SymmetricalAbnormal

Hyperkalemia

• Hyperkalemia = High Potassium Level– Peaked T-Waves

• May mimic an acute MI

– Sine Waves• Sign of lethally high potassium level

Sine Wave

Peaked T-Wave

Hyperkalemia

Hyperkalemia

Hyperkalemia

T-Wave Discordance

• Discordance means opposite.– T-Wave discordance means that the T-Wave

is deflected in the opposite direction as the terminal (last) wave of the QRS.

– T-Wave discordance is normal in every lead with Left or Right BBBs.

T-Wave Discordance

Digitalis Effect

• Shortened QT interval• Characteristic down-sloping ST depression• Dysrhythmias

– ventricular / atrial premature beats– paroxysmal atrial tachycardia with variable AV block– ventricular tachycardia and fibrillation– many others

QT-Interval

Normal QTc

< 460 ms

QT-Interval

Measures the time from when depolarization starts to the end of repolarization.

QTc = RR

QT

QT-Interval

Long QT Syndrome

• QTc > 460ms– Congenital

• Major contributor to sudden unexplained death in children and young adults.

– Drug induced• Caused by many arrhythmia medications

Long QT Syndrome

U-Wave

• Usually not visible.

• Should not be prominent.

• Should never be bigger than T-wave

Osborn Waves

• Sometimes called “J-Waves”• Indicates HYPOTHERMIA• May be associated with bradycardia• Extra wave at the J-Point of the QRS-

complex.

Osborn Waves

Osborn Waves

END

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