DEFINITION
Electrocardiography: It is a diagnostic procedure that graphically records the conduction, magnitude and duration of the electrical current generated by the heart.
Electrocardiograph: It is an instrument utilized to record the surface electrocardiogram (ECG). So, this is a sophisticated galvanometer, a sensitive electromagnet, which can detect and record changes in electromagnetic potential. It consists of:
- The electrodes: Located on the patient
- The cables: Attached to the electrodes
- An amplifier
- A galvanometer
- The write of mechanism: Effected through the galvanometer.
Electrocardiogram (ECG): It is a graphic recording of the electrical potentials or activity produced by cardiac tissue. By the placement of electrodes on selected areas of the body we usually record 12 views of the electrical activity. All four chambers of the heart are represented on this recording.
ECG is a graphic recording of electrical activity of the heart during the various events of cardiac cycle as recorded by placing the suitable electrodes on the surface of the body connecting them with a suitable galvanometer.
Willem Einthoven (1860–1927): Dutch physiologist and physician whose application of the string galvanometer to recording of the electrical activity of the heart lead to the development of clinical electrocardiography.
Augustus Desiré Waller (1856–1922): English physiologist who obtained the first ECG in man using a capillary electrometer.
WHAT TO LOOK FOR IN THE ECG? (HOW TO REPORT AN ECG?)
1. Name | : | Mr Hassan |
2. Age | : | 45 yrs |
3. Date | : | 14th June 2013 |
4. Rate | : | 110/min |
5. Rhythm | : | Sinus and regular |
6. P-wave | : | Tall and peaked in II, V1 |
7. P-R interval | : | 0.28 sec, and constant |
8. QRS complex | : | |
| : | 0.16 sec in V1 |
| : | Tall R in V1 |
| : | Normal or deep Q in II, III, aVF |
9. ST segment | : | Coved or raised or depression in 1, avL |
10. T-wave | : | Inverted in II, III aVF |
11. U-wave | : | Prominent in leads V3 – V6 |
12. The cardiac axis | : | −30° |
13. Comments | : |
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14. Additional remarks | : | Suggest exercise tolerance test (ETT) |
CLINICAL VALUE OF THE ELECTROCARDIOGRAM
The ECG is of diagnostic value in the following clinical circumstances:
- Atrial and ventricular hypertrophy/chamber enlargement/tachycardia or bradycardia
- Myocardial ischemia and infarction
- Pericarditis
- Systemic diseases that affect the heart
- Determination of the effect of cardiac drugs, especially digitalis and certain antiarrhythmic agents
- Disturbances in electrolyte balance, especially potassium (hypokalemia or hyperkalemia)
- Evaluation of function of cardiac pacemakers
- Analysis of abnormal rhythm.
- Arrhythmias
- Block—first degree block, sinoatrial (SA) block, bundle branch block
- Low voltage—in myxoedema, hypothermia, emphysema
- Exercise ECG to see coronary artery disease