title: [Léon Fredericq and the descending portion of the second positive wave (1st systolic wave) of the venous pulse: the negative cd or X wave in current nomenclature].
abstract: Understanding the venous pulse waves was a challenge for L. Fredericq. We show that his interpretation of the X depression previewed the nowadays visualization of the A-V valve movement through echography. We also present an a contrario demonstration on the same topic by observing that forcing a passive heart (Gad's experiment) cannot reproduce the atrial aspiration during the simulated ejection unlike it is in the beating organ.
mesh_terms: D006801:Humans; D008943:Mitral Valve / Q000502:physiology*; D009200:Myocardial Contraction; D011674:Pulse; D013318:Stroke Volume; D013599:Systole
vernacular_title: Léon Fredericq et la portion descendante de la seconde onde positive (1ère onde systolique) du pouls veineux: ondulation négative cd ou X dans la nomenclature actuelle.