An electrocardiogram (ECG or EKG) machine is a medical device used to record the electrical activity generated by the heart. This non-invasive test captures the heart’s rhythm and rate by detecting the electrical signals that coordinate muscle contractions. The resulting graph provides healthcare professionals with information on cardiac health, aiding in the diagnosis of conditions like arrhythmias or signs of a previous heart attack. It is a fundamental diagnostic tool utilized in medical offices, hospitals, and emergency settings worldwide.
Preparing the Patient and Equipment
Before beginning the procedure, the patient must be prepared to ensure the clarity of the tracing. The patient is asked to undress from the waist up and wear a gown, with privacy maintained. The ideal position is lying flat on the back (supine) or in a semi-recumbent position, with arms resting at the sides and legs uncrossed.
The skin where the electrodes will be placed must be prepared to reduce electrical resistance. Jewelry and metallic objects should be removed, and the skin cleaned with an alcohol wipe or abrasive prep pad to remove oils, lotions, or dead skin cells. Excessive chest hair must be clipped or shaved, as hair prevents the conductive adhesive from making firm contact. Simultaneously, the ECG machine should be powered on, checking that the lead wires are undamaged and the printer has an adequate supply of paper.
Applying the Electrodes
A standard 12-lead ECG requires the application of 10 electrodes, which are patches containing a conductive gel. These electrodes are divided into four limb leads and six precordial leads. The limb electrodes (Right Arm, Left Arm, Right Leg, Left Leg) are placed on the fleshy parts of the limbs, typically on the wrists and ankles, though shoulders and thighs are also acceptable. The Right Leg electrode often serves as the electrical ground to stabilize the signal.
The six precordial electrodes (V1 through V6) must be placed precisely on the chest using specific anatomical landmarks, which is essential for an accurate tracing.
- V1 is positioned in the fourth intercostal space (ICS) just to the right of the sternum.
- V2 is placed in the fourth ICS immediately to the left of the sternum.
- V4 is located in the fifth ICS in line with the middle of the clavicle (mid-clavicular line).
- V3 is positioned midway between V2 and V4.
- V5 is placed on the same horizontal level as V4, but at the anterior axillary line.
- V6 is placed on the same horizontal level at the mid-axillary line.
Ensuring firm adhesion and good skin contact for every electrode minimizes interference and helps produce a high-quality signal.
Acquiring the Tracing
Once all ten electrodes are in place, the machine is ready to acquire the tracing. The standard calibration for a resting ECG is a paper speed of 25 millimeters per second (mm/s) and a gain of 10 millimeters per millivolt (mm/mV). These settings ensure that the size and timing of the complexes are represented accurately. The patient must be instructed to remain still and breathe normally throughout the recording period, as movement can introduce interference.
During the recording, the technician must monitor the display for signs of artifact, which is electrical noise that distorts the cardiac signal. A slow, undulating baseline (wandering baseline artifact) indicates poor skin contact or patient breathing and can be corrected with better skin prep or securing a loose electrode. High-frequency jaggedness (somatic tremor) is caused by muscle tension or shivering and can be resolved by ensuring the patient is warm and relaxed. Electrical interference, which appears as a thick, fuzzy baseline, stems from nearby electronic devices or ungrounded equipment and may require unplugging non-essential items.
Post-Procedure Steps
After a satisfactory tracing has been acquired, the procedure must be concluded and documentation prepared. The electrodes must be removed gently, and any residual conductive gel or adhesive residue should be wiped away. The patient can then be assisted in redressing and resuming normal activities.
The printed or digital tracing must be labeled with the patient’s name, the date, and the time of the recording. Any deviations from standard electrode placement, such as an alternative lead site due to injury, should also be noted on the document. The technician’s role is to operate the equipment and obtain a clear tracing; interpretation of the electrical patterns for diagnosis is the responsibility of a qualified physician or cardiologist.