He published 360 papers on cardiovascular medicine from 1898 to 1945, covering the whole subject apart from congenital malformations.
Until 1910 his papers were concerned with general medicine, and after 1910 he focused on cardiology.
His book La Tension artérielle en Clinique, published in 1910, was the standard text on the measurement of blood pressure.
He realised the importance of electrocardiography, and published on arrhythmias, particularly ventricular tachycardia.
He studied angina pectoris, describing the syndrome in Les Angines de Poitrine in 1925; he maintained the belief that coronary artery disease was the cause.