Comparison of impedance cardiography and thermodilution-derived measurements of stroke volume and cardiac output at rest and during exercise testing.

BACKGROUND: Non-invasive evaluation of haemodynamic variables remains a preferable and attractive option in both pharmacologic research and clinical cardiology.
OBJECTIVES: The objective of this study was to evaluate the correlation, feasibility and diagnostic value of haemodynamic measurements by ICG with the thermodilution (TD) method at rest and during exercise testing.
METHODS: We measured stroke volume (SV) and cardiac output (CO) with both methods in 20 patients with suspected coronary artery disease (CAD). All measurements were performed simultaneously at rest and during bicycle exercise.
RESULTS: There was a highly significant correlation (p < 0.001) for measurements of SV between both methods at rest (r = 0.83) and during exercise (r = 0.85-0.87) with 50-100 watts. For measurements of CO, the respective correlations were r = 0.85 at rest and r = 0.92-0.94 during exercise. The mean difference for measurements of SV were 3.8 +/- 12.6 ml at rest and 6.5+/- 11.4 ml during exercise. For measurements of CO, the mean difference between both methods was 0.9 +/- 1.0 l/min at rest and 1.0+/- 0.8 l/min during exercise. Compared to TD measurements, ICG had a bias to overestimate SV and CO of approximately by 5-10%. One patient had to be excluded because of inappropriate quality of the ICG signals during exercise.
CONCLUSIONS: ICG is a feasible and accurate method for non-invasive measurements of SV and CO. Haemodynamic measurements by ICG were correlated highly significant to simultaneous measurements by the TD method.