Impedance cardiography
![Fig.1: Aortic blood pressure and aortic blood flow over one heartbeat interval: S = Systolic blood pressure; D = Diastolic blood pressure; MAP = Mean Arterial Pressure; SV = Stroke Volume; DN = dicrotic notch (aortic valve closure)](/Images/godic/202502/09/Relationship_between_Aortic_Blood_Pressure_and_Aortic_Blood_flow5206.png")
![Fig.5: The Frank-Starling Law and Inotropy: Three Frank-Starling curves shown for normoinotropy, hyperinotropy and hypoinotropy. A patient, who is normovolemic and normoinotropic, exhibits normal level of Ejection Phase Contractility (EPC). However, a patient who is hypovolemic can exhibit the same normal level of EPC if given positive inotropes, and a patient who is volume overloaded (hypervolemic) can also have normal level of EPC if given negative inotropes](/Images/godic/202502/09/Frank-Starling_Law_and_Inotropy5206.png")
Impedance cardiography (ICG) is a noninvasive technology measuring total electrical conductivity of the thorax and its changes in time to process continuously a number of cardiodynamic parameters, such as Stroke Volume, SV, Heart Rate, HR, Cardiac Output, CO, Ventricular Ejection Time, VET, Pre-ejection Period and used to detect the impedance changes caused by a high-frequency, low magnitude current flowing through the thorax between additional two pairs of electrodes located outside of the measured segment. The sensing electrodes also detect the ECG signal, which is used as a timing clock of the system.