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(Hypertension. 2003;41:e7.)
© 2003 American Heart Association, Inc.

Letters to the Editor

Response

Cardiovascular Magnetic Resonance Unit, Royal Brompton Hospital, London, United Kingdom

An extract of the first 250 words of the full text is provided, because this article has no abstract.

In comparing 2 methods for assessing the same variable, it is usually the limits of agreement (the spread of the results) that are more important than the mean difference (net bias), which usually follows a regression toward the mean and can in principle be zero, despite obvious differences between measurement techniques. In our paper, the 95% confidence intervals were ±57.6 g and ±46.3 g for M-mode and 2D (Reichek formula), respectively, when compared with 3D CMR measurements, with mean differences of -14.3 g and -2.6 g, respectively. It is unsurprising that different papers may vary in the mean differences between techniques, given the different populations studied and the wide variety of left ventricular shape, but we note the very similar limits of agreement for both M-mode and the Reichek formula between our study and the correspondents’ paper (in press). For serial studies, it is again this spread of values (interstudy reproducibility) that is of prime importance in assessing individual and group changes, and it was noteworthy that the limits of agreement for the serial changes in our study were very similar to those for the baseline measurements.

We did not set out to test all available echocardiographic formulas. The intention was to test the reliability of the principle of calculated formulas with an assumed geometric shape against direct measurement, and we chose a commonly used and simple formula for 2D measurement, as well as the most widely used M-mode formula. To compare many different formulas would have been cumbersome and . . . [Full Text of this Article]