An ECG (electrocardiogram) shows how the heart is beating by recording its electrical activity.
What an ECG Measures
An ECG is a non-invasive test that uses electrodes to detect and record the electrical signals produced by the heart. These signals control the heart's contractions. The ECG machine translates these signals into a waveform that can be analyzed by healthcare professionals. The waveform provides information about:
- Heart Rate: How fast the heart is beating.
- Heart Rhythm: Whether the heart is beating in a regular or irregular pattern.
- Strength and Timing of Electrical Signals: Reveals if electrical impulses are normal as they travel through the heart.
- Damage to the Heart Muscle: Indications of previous heart attacks or areas with reduced blood flow.
- Electrolyte Imbalances: Abnormal levels of electrolytes like potassium and calcium can affect the ECG.
How the ECG Procedure Works
- Electrode Placement: Small, sticky patches called electrodes are attached to the skin on the chest, arms, and legs. These electrodes are sensors that pick up the heart's electrical signals.
- Signal Transmission: The electrodes are connected to an ECG machine via wires.
- Recording: The ECG machine amplifies and records the electrical signals. This information is displayed as a waveform on a screen or printed on paper.
- Interpretation: A trained healthcare professional, such as a doctor or cardiologist, interprets the ECG waveform to assess the heart's function.
Interpreting the ECG Waveform
The ECG waveform is composed of several distinct components, each representing a different phase of the heart's electrical cycle:
- P wave: Represents atrial depolarization (the electrical activity that causes the atria, the upper chambers of the heart, to contract).
- QRS complex: Represents ventricular depolarization (the electrical activity that causes the ventricles, the lower chambers of the heart, to contract).
- T wave: Represents ventricular repolarization (the electrical recovery of the ventricles).
The shape, size, and timing of these components are analyzed to identify any abnormalities. For example:
| ECG Component | Potential Abnormality | Possible Condition |
|---|---|---|
| P wave | Absent or abnormal shape | Atrial fibrillation, atrial flutter |
| QRS complex | Wide or tall | Ventricular hypertrophy, bundle branch block |
| T wave | Inverted or elevated | Myocardial ischemia, hyperkalemia |
| ST segment | Elevated or depressed | Myocardial infarction (heart attack), angina |
Conclusion
An ECG is a valuable diagnostic tool that provides a visual representation of the heart's electrical activity, allowing doctors to assess heart rate, rhythm, and identify any abnormalities that may indicate underlying heart conditions.
