Today our topic of discussion is Electrocardiogram of Medical Surgical Procedures.
Electrocardiogram of Medical Surgical Procedures
ELECTROCARDIOGRAM
Electrocardiogram (ECG) invented by Enthovan in 1901 (Fig. 29.89). It is a permanent record of the electrical activity of the heart. It is a tracing made of the various phases of the heart action by means of an electrocardiography.It is a graphical representation that describes about the heart.
The electrocardiogram is an instrument which detects very small electrical signals, generated by depolarization and repolarization of the myocardium. Electrodes are attached to the limbs and chest of the patient, and electrical changes are amplified and recorded on a moving paper.
Normal Conduction System of the Heart
The electrical impulse is generated in the sino-atrial node (pacemaker) of the heart. It spreads through the both atria and cause atrial contraction. It crosses the atrioventricular node and is passed down through right and left bundle branches and finally reaches the Purkinje fibers, where the ventricular contraction takes place.
Purpose of ECG
- Electrocardiogram is the most important signal tool for the diagnosis of arrhythmias
- It is helpful to study the cardiac functions-rate, rhythm and axis
- It helps to diagnose cardiac disease condition: myocardial infarction, injury, ischemia and hypertrophy
- It helps to detect electrolytes imbalance hyperkalemia
- To give valuable diagnostic information about cardiac
- function To confirm the coronary heart disease in most cases
- To demonstrate cardiac arrhythmias such as ventricular tachycardia and heart block.
Components of ECG
Electrocardiography consists of waves, complexes and intervals.
- Wave or complex: It is a deflection that can be positive or negative wave-atrial depolarization QRS complex- ventricular depolarization. T wave- ventricular repolarization.
- Segment: A is the period of time between a wave or complex, e.g. ST-segment
- Interval: An interval is the time between two points on the ECG, e.g. PR-interval
- Time duration (normal) for the P-wave-0.08 seconds PR-interval less than 0.20 seconds (average 0.16 seconds), QRS complex-0.08 seconds, ST segment 0.12 seconds and T-wave-0.16 seconds.
ECG Graph Sheet
- ECG tracing are recorded on graph paper, which is divided into small (1/1 mm) squares light lines and large (5/5 mm) squares by heavier lines.
- Horizontal lines (Y-axis) measures the amplitude (voltage), one small square represents 1 mm and a large square represents 5 mm or 0.5 mm. .
- The vertical lines (X-axis) measure time, each small square represents 0.20 seconds.
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