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In their population-based study, Chahal et al. (1) reported average values of 49 ± 9 ml/m2 and 42 ± 8 ml/m2 for 3-dimensional echocardiography (3DE) end-diastolic volumes (EDV) in healthy European men and women, respectively. These volumes are significantly lower than those reported by other researchers who performed similar studies: 66 ± 10 ml/m2 and 58 ± 8 ml/m2, respectively, found by Aune et al. (2); and 55 ± 7 ml/m2 and 49 ± 6 ml/m2, respectively, reported by Kaku et al. (3) for the same age group. Even Fukuda et al. (4), who studied a Japanese population (significantly smaller body size than Europeans), found larger EDV: 50 ± 12 ml/m2 and 46 ± 9 ml/m2 in men and women, respectively. Interestingly, none of these previous studies has been referenced and discussed by Chahal et al. (1).
On the other end, the upper normal values (mean values ±2 SD) for 3D end-diastolic and end-systolic volumes reported by Chahal et al. (1) (e.g., 67 ml/m2 and 29 ml/m2, respectively, in males) are lower than the 2-dimensional echocardiography (2DE) upper normal limits reported in current guidelines (75 ml/m2 and 30 ml/m2, respectively) (5), contradicting all previous studies showing a greater underestimation of volumes measured by 2DE than by 3DE. Finally, making a simple calculation from the data provided in Table 1 in that paper (1), it seems that the European subjects were in low-flow state (stroke volume index 30 ml/m2 in men and 26 ml/m2 in women).
These data raise the issue of the accuracy of the measurements performed in this study, particularly when no reference (or at least comparison) modality, such as the simple stroke volume measured with 2DE and Doppler, has been provided. One possible explanation of the underestimation of the left ventricular volumes reported by Chahal et al. (1) may be the limited experience of the sonographers who performed measurements as stated by the authors (“ … all underwent a 4-week period of training in 3DE volume acquisition and off-line analysis by the vendor representative at the beginning of the study”) and underlined in the accompanying editorial (6). The effect of the reader experience on accuracy of 3D left ventricular volume measurements has been documented (7).
We concur with the idea that development of normative values is the first step for effective application of 3DE in clinical routine (6), and a meta-analysis of existing data could be a good start (8). However, there is a clear need to check the reliability of the data, too. Comparison with existing data and internal validation with stroke volume obtained by 2D and Doppler echocardiography may be a simple and practical way of checking results.
“However beautiful the strategy, you should occasionally look at the results.”
—Sir Winston Churchill (9)
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