Evaluation of left ventricular function by impedance cardiography: a review.

There are a number of different methods by which the impedance waveform can at least partly predict ventricular function. Of these methods, the measurement of systolic time intervals has been best validated. However, much work still needs to be done on a wide variety of ICU and non-ICU patients to validate a stable and predictable relationship between PEP/VET and EF. Further work may also validate the other indices discussed above, but less confidence can be expressed as to their eventual clinical use at present. All of the work to date has examined the relationship between impedance and LV function. Although the impedance tracing is known to largely reflect LV ejection and aortic root flow, there may be some contribution from right ventricular function. To further evaluate this contribution, work using first-pass radionuclear techniques to selectively look at right ventricular EF will need to be done.