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The term "dicrotic" means double beat. The dicrotic notch and the ensuing wave seen in the arterial pressure record is the pressure transient produced when the aortic valve closes at the end of left-ventricular ejection. It is also present in the pulmonary artery pressure record and signals closure of the pulmonic valve; yet its existence was doubted for many years. In the late 1800s, physiologists and clinicians argued for years over its existence; this is the story of that controversy.