Cardiography is the diagnostic recording of the heart's activity by electronic means. This tool is used to create a variety of cardiographic readouts, such as electrocardiograms, electrocardiographs, echocardiographs, and impedance cardiographs, all of which fall under the umbrella term of cardiography. It is used to test, diagnose, and monitor problems relating to the heart and the flow of blood throughout the body.
A traditional cardiogram is printed out on special graph paper as the readout is being measured. The paper contains a grid of 0.04 inch (1 millimeter) squares. Cardiograph machines can change the speed of output, but there are certain velocity standards that are generally adhered to when conducting a cardiograph test.
The sensors used during a cardiogram are called electrodes. In most instances, 10 electrodes are applied to various parts of the body. After the electrodes are smeared with a special conducting gel, they are affixed to the skin. Generally, electrodes are placed on the right and left arms, the right and left legs, and across the chest and abdomen.
The electrocardiography type of cardiography provides a reading of the heart's activity over a certain period of time. The information is transmitted via the sensors placed on the skin. A noninvasive testing modality, electrocardiography senses and enhances the electrical impulses of the skin as the heart beats, offering an analysis of the heart's movement via an electrocardiogram or electrocardiograph. This form of cardiography was first fashioned in the 1870s by a medical student named Alexander Muirhead. Muirhead was able to detect a patient's heartbeat through attaching wires to the patient's wrist; as the technology has advanced, more sophisticated wiring is used and a greater number or sensors are placed in various locations around the body.
Echocardiography is a style of cardiography that employs the use of sonar to accurately measure a patient's heart activity. Ultrasound technology allows a cardiographer to move a sonar instrument over the body of the patient, providing a real-time reading of that patient's heart function. Echocardiography is widely known as a cardiac ultrasound.
Impedance cardiography (ICG) is a hemorheology technique that senses the flow of blood through the thorax. This testing method can help determine any number of issues associated with the heart and the flow of blood, including heart disease, heart dysfunction, and stroke. An ICG reading provides medical professionals with a wealth of information, including heart rate, cardiac output, stroke volume, stroke index, and the velocity index of blood flow through the aorta.