The impedance cardiogram, also known as ICG signal, is obtained using bioelectrical impedance (Bio-Z) technology and reflects the changes in blood volume.
Each cardiac cycle produces identifiable markers in the ICG waveform:
- Point A – Appears as a downward deflection in the ICG signal, caused by atrial contraction.
- Point B – Opening of semilunar valves (start of ventricular rapid ejection)
In the ICG signal, it is characterized as the onset of the systolic wave, corresponding to the moment of maximum increase in blood flow acceleration - Point C – Peak aortic blood flow ((dZ/dt)max), marking the end of the rapid ejection phase and the transition into the reduced ejection phase.
In the ICG signal, it is characterized as the peak (maximum value) of the systolic wave. - Point X – Aortic valve closure: Represents the end of ventricular systole and the beginning of semilunar valve closure.
In the ICG signal, it is characterized as the minimum value following the systolic wave (varying with heart rate) and corresponds to the point of maximum increase in blood flow deceleration. - Point O – Represents the opening of the left atrioventricular valve and the onset of ventricular filling.
Two important measurements:
- (dZ/dt)max → Used to determine peak blood flow
- B–X interval → Represents LVET (Left Ventricular Ejection Time)
Based on the positions and amplitudes of these characteristic points, enables accurate stroke volume calculation and cardiac performance evaluation.
Related Article:
What is Impedance Cardiography (ICG) and how does it measure stroke volume?