Assessment of cardiac performance: short- and medium-term variability of impedance cardiography at rest and during dynamic exercise.

Short- and medium-term variability of impedance cardiography at rest and during exercise at a heart rate of 155-160 beats/min were assessed in 12 healthy men aged 21-28 years. Two consecutive measurements within 1 min were performed 4 times at 2-hour intervals on 2 days 14 days apart. Ejection fraction was the most reproducible of all impedance cardiography parameters, the CV ranging from 3.3-5.9%. The short-term reproducibility of cardiac output and stroke volume at rest was good, the between-repeats coefficient of variation (CV) being 4-6%. The reproducibility weakened with longer time span (between-day CV being about 12%) and higher heart rates (exercise). However, even the between-day reproducibility at rest was as good as that of heart rate. Between-day CV during exercise were about 20%.