Electrocardiogram of the heart

The electrodes are fixed over the chest, both handsand legs.

The results are recorded on graph paper

The recording of the heart takenafter mild to moderate exercise is called as

heart stresstest (stress ecg) or Tread Mill Test

Electrocardiogram reading is used to analyze....

• The rate of heart

• Normal and abnormal rhythm of heartbeats.

• The size and enlargement of the heart.

• Effects of drugs on the heart function.

• Toxicity of certain drugs

• Damage of the heart.

• Function of a device on heart like pacemaker.

• disease of the pericardium (covering layer of heart)

• metabolic changes of the body which alters the recording.

• Location of ischemia or infarction.

• Other heart diseases.

Risk factors for Electrocardiogram

ECG is painless test.

Manypatients refuse to do this test for the fear of pain and shock.

Hence there is no electricity is emitted from the machine itself. no chance for shock at all.

Very rarely patient may get skin allergies by putting the electrode disks overthe skin.

12 Lead Electrocardiogram and Lead Placement

Leads Connections

Bipolar

LeadI Right arm-Left arm

LeadII Right arm-Left leg

LeadIII Left arm-right leg

Unipolar

aVR Right arm

aVL Left arm

aVF Left foot

Chest Leads

V1,V2 V3 V4 V5 and V6

Interpretation of ECG

Normal ECG contains P,Q,R,S and T waves.

Irregular changes in these waves shows ischemic and infarction changes.

What is t waves and changes in Heart attack

T wave changes gives the clue for myocardial infarction.

T wave inversion shows the sign ofinfarction.

It is seen in the leads adjacent to the site of infarction.

Hyper acute elevation of t wave is seen in preceding ST segment elevation.

Area of infarction and ecg changes

ST segment elevation is seenin the leads adjacent to the site of infarction.

Leads II,III and aVF ------ Inferior(Lower) wall of the heart.

Leads V1,V2 and V3 ------ Anterior(Front) wall of the heart.

Leads V3 andV4 ------ Septal wall(the wall which divides the heart inthe midline)

Other leads may show reciprocal ST segment depression.

Absence of Q waves indicates thehigher risk for subsequent heart attack.

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