Simultaneous non-invasive assessment of arterial stiffness and haemodynamics - a validation study

The purpose of the study was to estimate the reliability of whole-body impedance cardiography (ICGWB)-derived pulse wave velocity (PWV) and stroke volume index to pulse pressure (SI/PP) measurements. The repeatability and reproducibility of ICGWB parameters were also determined. Agreement between the impedance and Doppler ultrasound-based PWV measurements was estimated in 25 healthy subjects in two consecutive measurements. Impedance-derived SI/PP (SIICG/PP) estimates were compared with simultaneously measured SI/PP based on thermodilution (SITD/PP) and direct Fick (SIFICK/PP) methods in 30 surgical patients. PWV measured between the aortic arch and popliteal artery using the impedance technique with selective electrode configuration (PWVIS) agreed well with the Doppler ultrasound method (PWVDOPP), the bias (PWVDOPP - PWVIS) and precision (+/- SD of differences) being 0.00 and 0.79 m s-1, respectively. PWV derived from the whole-body and popliteal impedance plethysmograms (PWVICG) overestimated slightly PWVDOPP values. The repeatability value for PWVIS was excellent, being 0.54 m s-1. The reproducibility values for PWVDOPP and PWVIS were very similar (2.17 and 2.42 m s-1, respectively). Changes in PWVIS correlated strongly with changes in PWVDOPP (r=0.74; P<0.0001), indicating that both methods reflected the true physiological variation in PWV. The agreement between SIICG/PP and SITD/PP or SIFICK was almost identical to the agreement between the SITD/PP and SIFICK/PP. In conclusion,whole-body impedance cardiography provides handy and reliable means of evaluating arterial stiffness on the basis of PWV and SI/PP simultaneously with conventional haemodynamic parameters. The method is highly repeatable and reproducible.