Repeatability of measurements of pulmonary venous flow indices

We investigated the measurement repeatability of four pulmonary venous flow indices. The indices were measured on 45 anonymised, transthoracic Doppler recordings of adequate technical quality. Measurements were taken by two independent observers, and repeated after 10 days. Plus/minus the repeatability coefficient, which was used to quantify repeatability, gives the 95% probability limits for random variation between repeated measurements. The index D-diff, which is the difference in duration of the pulmonary venous flow reversal during atrial systole and the transmitral A-wave, had repeatability coefficients of 50 and 57 ms intra- and inter-observer. For the fraction of antegrade pulmonary venous flow during ventricular systole, the coefficients were 12 and 13 percentage points, but improved to 6 and 7 among the high-quality recordings. The retrograde pulmonary venous flow during atrial systole as a fraction of the antegrade flow, had coefficients of 5 percentage points both intra- and inter-observer. The coefficient for the peak velocity of retrograde pulmonary venous flow was 0.05 m/s intra- and inter-observer. Thus, the systolic fraction was the only index that showed a satisfactory repeatability. We suggest that if the other indices are used, measurements should be taken by a blinded observer to avoid observer bias.