Background/aims: Measurement of cardiac output in hyperkinetic patients with cirrhosis by Doppler echocardiography is increasingly reported, but has not been validated. We have compared simultaneous measurements of cardiac output by Doppler echocardiography (CO(d)) and by the indicator dilution technique (CO(I)).
Methods: Twelve patients with cirrhosis were studied. CO(d) was measured as the spatial mean velocity of the left ventricular outflow tract, multiplied by the cross-sectional area and the heart rate. CO(I) was determined by the standard indicator dilution technique after injection of 125I albumin and 99mTc albumin into the right atrium and subsequent sampling from the femoral artery.
Results: The mean CO(d) and CO(I) were similar (7.20 vs 7.15 l/min, NS). A highly significant correlation was present between CO(d) and CO(I) (r = 0.86, P < 0.0001; slope 0.91, Y(0) = 0.78 l/min). However, the mean squared difference between CO(d) and CO(I) was 2.3 (l/min)2. A Bland-Altman plot revealed no trend with the level of cardiac output. The standard deviation (0.79 vs 0.30 l/min, P < 0.01) and the coefficient of variation (10.5 vs 4.2%, P < 0.01) of duplicate measurements were significantly higher with the Doppler technique.
Conclusion: Doppler measurements of cardiac output in groups of patients with cirrhosis are accurate with respect to the group mean, but marked disagreements of over- and underestimation were seen in individual patients. The reproducibility of the Doppler technique is acceptable, although not as good as that of the indicator dilution technique.