Anatomy. ECG Electrodes ECG Waveform The 12 lead ECG.

Anatomy

ECG Electrodes

ECG Waveform

The 12 lead ECG

How does the heart work

AV node activated by Atrial depolarizationSends signal through His-purkinje bundleGet depolarization of SEPTUM

Left and Right BUNDLES transmit signal to Left and Right VENTRICLESNet “Vector” towards the LVShould be narrow (<120msec) if bundles working properlyThen have REPOLARIZATION = Twave

The appearance of this electrical activity depends on which lead you are using to look at it

Review of waveforms

How to Look at an ECG• Rate: Is the heart rate too fast or slow?• Rhythm: Sinus rhythm or not?• Axis: Where does the majority of

electrical activity point?• P wave: How big are the atria?• PR interval: How healthy is the AV node?• QRS wave: Is there abnormal conduction

or a ventricular source?• QT: Long is bad• Ischemia and hypertrophy

ECG PaperCan Determine Heart Rate

Rule: 300, 150, 100, 75, 60, 50 counting over for each big sqaure

What is the heart rate?

Answer = 75 per min

Rhythm : Is there a p wave? = Sinus

Is it followed by a QRS?

Is the rhythm regular or irregular?

Reasons to have an irregular rhythm

• Irregular pacemaker– Multifocal atrial

rhythm

– Atrial fibrillation

– Atrial fib/flutter

• Ectopic beats– PVC

– PAC

– PJC

• Irregular conduction– AV node block

• 1st degree:– PR interval > 200 msec

• 2nd degree:– Type 1: Wenkebach

– Type 2: dropped beat

• 3rd degree:– p waves marching

independent to QRS

Examples of Rhythms

Multifocal Atrial Rhythm

AFIB

Atrial Flutter

AFIB

V TACH

Example of a PVC

Telling the Axis from the leads

The axis wheel

The P wave

The QRS

QRS < 120 msec

QRS > 120 msecRabbit ears in V1 & V2

Wide S wave in V5 & V6

R axis deviation

QRS > 120 msecDeep slurred S wave in V1

Wide R wave in V6, I & avL

L axis deviation

Ishcemia vs Acute Infarct

Example of Ischemia

Examples of Infarctions

Review• Rate: Is the heart rate too fast or slow?• Rhythm: Sinus rhythm or not?• Axis: Where does the majority of

electrical activity point?• P wave: How big are the atria?• PR interval: How healthy is the AV node?• QRS wave: Is there abnormal conduction

or a ventricular source?• QT: Long is bad• Ischemia and hypertrophy

Describe this ECG

Describe this Strip