ELECTROCARDIOGRAM INTERPRETATION

ELECTROCARDIOGRAM (ECG)

Electrocardiogram is a graphic record of algebraic summed potentials generated by the heart, recorded from the surface of the body using an electrocardiograph machine.

The magnitude, polarity, and configuration of the recorded electrocardiogram depends on the location of the recording leads placed on the body surface. The process of recording an electrocardiogram is called electrocardiography.

Aims and Objectives

Carry out electrocardiography correctly and successfully.
Interpret the electrocardiogram recorded.
Relate the interpretation with the heart status.
Assess the functional integrity of the heart.
Suggest the appropriate remedy if any that can improve the status detected.

Requirements

Functional Electrocardiograph machine & accessories
Volunteer subject
Volunteer ECG operator
Couch with linen
Screen (for privacy)
Cotton wool/tissue and spirit/alcohol

Procedure

The lab technician/tutor will introduce the electrocardiograph machine in use with its operational procedures.
The procedure of electrocardiography will be thoroughly explained to the volunteer subject by the volunteer operator.
The subject will be screened off, asked to undress to expose the chest, both upper limbs and both legs.
The subject then lies on his or her back on the couch, and relaxes while breathing quietly throughout the procedure.
The rest of the body surface that is not to be used is covered with linen.
The volunteer ECG operator prepares the surfaces for the leads electrodes attachment by clearing it with cotton wool soaked in alcohol or spirit.
Thinly coat the surfaces prepared with salt enriched electrode jelly and proceed to strap electrodes appropriately.
Record manually lead by lead till you get all the 12 leads designated, then proceed to record automatically all the 12 leads record as well.
Label the electrocardiogram recorded with the volunteer's particulars namely: Name, Sex, Age, time of recording, any medicines taken, and finally any known medical condition the volunteer subject has.
Switch off the electrocardiograph machine and disconnect off the subject.
Clean off the jelly applied on the subject with water and dry with cotton wool or tissue.

Results

Analysis of Results

Note: Attached is a tracing of a normal 12 lead electrocardiogram (ECG) and the relationship of the events of the cardiac cycle to the waves and intervals of the normal left ventricular surfaces complex. Use these to help you analyze your recorded ECG.

1. Estimate the frontal and horizontal plane QRS axes:

2. Describe the atrial pace maker and indicate its rate and regulating:

3. Describe the nature and duration of atrial activation (P wave):

4. Describe any supra ventricular premature contractions:

5. Describe the AV junction conductions:

6. Describe the rate duration and regularity of ventricular activation and site of its pace maker (QRS complex wave):

7. Describe the course of ventricular activation and the shape of the QRS complex:

8. Describe any abnormalities in J point and S-T segments:

9. Describe T wave changes:

10. Describe alteration in Q-T interval in relation to rate:

Conclusion

Recommendation / Suggestions

Discussion Questions

1. What is the significance of:

i. P wave:
ii. QRS complex:
iii. T wave:

2. Why is P wave usually largest in standard lead II?

3. Why is T wave small or absent in lead aVL?

4. What is the significance of the interval between the end of P wave and the beginning of the QRS complex?

5. What factors influence the duration of the:

i. P-R interval:

ii. Q-T interval:

Reference: A Normal 12-Lead Electrocardiogram Layout

I

aVR

V1

V4

II

aVL

V2

V5

III

aVF

V3

V6

Physiology Steeplechase: ECG Interpretation

ECG Steeplechase

Experiment: Electrocardiography

Must Know:

Waves: P (Atrial), QRS (Ventricular), T (Repolarization).
Calculations: 300 / Big Squares = Rate.
Placement: V4 is at the Apex (5th ICS, Mid-Clavicular).
Pathology: ST Elevation = Infarction.

Doctors Revision