Electrocardiography (ECG)
Also known as: ECG, EKG
Electrocardiography is the recording of the heart's electrical activity through electrodes placed on the skin. The resulting tracing, an electrocardiogram (ECG or EKG), displays the heart's rhythm and conduction as a series of characteristic waves.
Electrocardiography is a noninvasive diagnostic technique that records the electrical impulses generated by the heart as they spread through the cardiac conduction system. Electrodes attached to the limbs and chest detect these small voltage changes at the skin surface, and the machine plots them over time as a tracing called an electrocardiogram (abbreviated ECG or EKG).
Each heartbeat produces a repeating waveform. The P wave reflects atrial depolarization as the impulse leaves the sinoatrial (SA) node and spreads across the atria; the QRS complex reflects ventricular depolarization, the powerful signal that triggers ventricular contraction; and the T wave reflects ventricular repolarization as the ventricles reset for the next beat. Intervals between these waves — such as the PR interval and QT interval — measure how long conduction takes through each part of the pathway.
A standard diagnostic study uses 10 electrodes to generate a 12-lead ECG, viewing the heart's electrical activity from twelve angles. Clinicians use the tracing to evaluate heart rate and rhythm, detect arrhythmias and conduction blocks, and identify signs of ischemia, infarction, chamber enlargement, and electrolyte disturbances. Proper skin preparation, correct electrode placement, and a still, relaxed patient are essential for an artifact-free tracing.
The CCMA (Certified Clinical Medical Assistant) exam tests electrocardiography as a core clinical skill. Candidates should know the conduction pathway, the meaning of each wave and interval, correct lead placement for a 12-lead ECG, and how to recognize common artifacts and troubleshoot a poor-quality tracing.
Key takeaways
- Electrocardiography records the heart's electrical activity through skin electrodes, producing an ECG/EKG tracing.
- The P wave shows atrial depolarization, the QRS complex ventricular depolarization, and the T wave ventricular repolarization.
- A standard 12-lead ECG uses 10 electrodes to view the heart from twelve electrical angles.
- ECGs are used to assess rate, rhythm, conduction, ischemia, and electrolyte effects.
- The CCMA exam tests conduction anatomy, waveform meaning, lead placement, and artifact troubleshooting.