Cardiographic impedance works by measuring changes in the electrical electrical impedance of the thorax as the blood volume changes with each heartbeat.
By analysing these changes, this technique estimates important cardiovascular parameters such as the volume of blood ejected by the heart to the peripheral arteries.
These
Results help clinicians assess cardiac and arterial status in order to adjust drug treatment more effectively.
How is an impedance cardiography test performed?
Electrodes are placed on the patient's skin, usually around the neck and on the chest. These electrodes are used to send a low-level electrical current through the chest.
The device sends an electrical current through the body and measures the voltage drop. Changes in impedance are detected and recorded by the impedance cardiography technology.
With each heartbeat, blood is ejected into the arteries and veins. This ejection causes changes in blood volume in the chest, which changes the impedance. The device detects these changes in impedance during the cardiac cycle.
What does impedance cardiography mean?
Impedance refers to the resistance of a material to the passage of an electric current. With impedance cardiography, small electrical currents are sent through the body, and the resistance (or impedance) to this current is measured.
The electrical impedance of the thorax changes according to the volume of blood in the thoracic cavity. During the cardiac cycle, as the heart pumps blood through the arteries, the volume of blood in the thorax changes, affecting the electrical impedance.
What are the advantages of assessing this interaction?
It is a non-invasive examination, requiring no special preparation or invasive procedures.
It provides continuous, real-time monitoring of heart function.
What measurements are obtained through the assessment of this interaction?
Changes in impedance are used to create a curve corresponding to the cardiac cycle. By analyzing this curve, the device can estimate various parameters of cardiac function:
Stroke volume (SV): The volume of blood pumped by the heart with each beat. Impedance cardigraphy (ICG) can estimate SV based on changes in thoracic impedance.
Cardiac output (CO): The total volume of blood pumped by the heart per minute. It is calculated using stroke volume and heart rate.
Peripheral resistance: This is the resistance that blood encounters as it flows through the peripheral arteries. Peripheral resistance plays a crucial role in regulating blood pressure and blood flow. Increased resistance can lead to increased blood pressure and decreased blood flow to tissues and organs.
Heart rate (HR): The number of heart beats per minute, measured directly or inferred from the impedance curve.