Electrocardiography (ECG) is a crucial diagnostic tool used in veterinary medicine to assess the electrical activity of an animal’s heart. It provides valuable insights into heart rate, rhythm, and potential cardiac abnormalities.
Understanding ECG
An ECG records the electrical impulses that travel through the heart during each heartbeat, which is the process where the electrical activity of the heart is generated by the movement of charged ions (like sodium, potassium, and calcium) across the cell membranes of cardiac muscle cells, which occurs through specialized channels that open and close in a coordinated manner, creating an electrical impulse that triggers the heart muscle to contract and pump blood. These impulses are displayed as waveforms on an ECG machine, allowing veterinarians to analyze heart function.
The key components of an ECG reading include:
P wave – Represents atrial depolarization, the first electrical pulse generated by the sinoatrial (SA) node. This triggers the contraction of the atria, allowing blood to flow into the ventricles.
QRS complex – Represents ventricular depolarization, where electrical impulses travel through the atrioventricular (AV) node and the bundle branches, causing the ventricles to contract and pump blood to the lungs and the rest of the body.
T wave – Represents ventricular repolarization, the recovery phase where the ventricles reset electrically to prepare for the next heartbeat.
U wave – A small, often unnoticed wave that follows the T wave. It is thought to represent repolarization of the Purkinje fibers or delayed ventricular repolarization. Its presence can sometimes indicate electrolyte imbalances or other cardiac abnormalities.
In parts 2 and 3, we talk about how electrodes pick up all these electrical signals from the heart and what the best practices are to have a nice reading on your ECG monitor.
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