title: [Cardiac Doppler. Gradients theory].
abstract: The authors remind of the theoretical basis which establish the validity of the Doppler method in the evaluation of valvular stenosis, and the origin of Bernouilli's formula: P1 - P2 = 1/2 p (v1-v2), in which P1 v1 represent pressure and speed proximal to the stenosis, and P2 and v2 represent pressure and speed at the level of the stenosis. This Bernouilli formula is only a particular case of the general law of preservation of mass and energy. Bernouilli's equation may only be applied under certain, well defined, conditions: isolated stenosis, short, not tunnel-shaped, exceeding 0.1-0.2 cm2: under this threshold, the trans-stenotic flow becomes spray with loss of the definition of the Doppler signal. The reliability of this equation is the basis for the reliability of the Doppler in the evaluation of all valvular stenoses by their instant and intermediate gradients.
authors.affiliation: Service de Cardiologie, Hôpital Sud, Amiens.
authors.forename: J P
authors.initials: JP
authors.lastname: Lesbre
authors.forename: D
authors.initials: D
authors.lastname: Choquet
authors.forename: C
authors.initials: C
authors.lastname: Mertl
mesh_terms: D015150:Echocardiography, Doppler; D006801:Humans; D014465:Ultrasonics
vernacular_title: Le doppler cardiaque. Théorie des gradients.