Normal Reference Ranges for Echocardiography: rationale, study design, and methodology (NORRE Study).

Background: Availability of normative reference values for cardiac chamber dimensions, volumes, mass, and function is a prerequisite for the accurate application of echocardiography for both clinical and research purposes. However, due to the lack of consistency in current echocardiographic 'reference values', their use for clinical decision-making remains questionable.
Aims: The aim of the 'Normal Reference Ranges for Echocardiography Study (NORRE Study)' is to obtain a set of 'normal values' for cardiac chamber geometry and function in a large cohort of healthy Caucasian individuals aged over a wide range of ages (25-75 years) using both conventional and advanced echocardiographic techniques.
Methods: The NORRE Study is a large prospective, observational multicentre study in which transthoracic echocardiographic studies will be acquired in 22 laboratories accredited by the European Association of Cardiovascular Imaging and in one laboratory in the USA accredited by ICAEL. The final sample size has been estimated in 1100 normal subjects in whom M-mode, 2D, and 3D imaging, colour Doppler, pulsed-wave Doppler, pulsed-wave tissue Doppler, and colour tissue Doppler imaging data will be obtained. All studies will be sent to a central echocardiographic core laboratory for quantitative analysis. Multiple studies will be performed for reproducibility analysis.
Conclusion: After completion of the NORRE Study, uniform reference limits according to age, gender, and anthropometric parameters will be available to standardize the quantitative interpretation of echocardiography.