The ECG Signal

Your heart is an incredibly powerful and complex muscle that works constantly because, unlike other types of muscle, the cardiac muscle never gets tired. You can measure your heart’s action through the skin by recording the electrical signals generated by the nerves that control the heart beat. The pattern of these nerve impulses is known as an electrocardiogram (ECG) and gives a great deal of information about how your heart is working. Medick’s MHM 100 Personal Heart Reporting Service allows you to monitor the health of your heart via regular ECG tests without having to visit your doctor. The shape of your ECG trace is as follows:

The heartbeat is generated by electrical activity in a cluster of cells called the sinoatrial node which is situated near the top of the atrium. The P wave represents the spread of electrical activity from the sinoatrial node through the atrium which then contracts and pumps blood into the ventricle. The QRS section of the wave represents the spread of the electrical impulse through the ventricular muscle during which the ventricles contract to pump blood into the body. The T wave represents the period of recovery for the ventricles before the next heartbeat.