The tricuspid component of the first heart sound in mitral stenosis

The sound of tricuspid valve closure has been identified in 35 of 40 phonocardiograms of patients with mitral valve disease. Identification of the sound is facilitated by the delay of closure of the mitral valve thus separating these 2 components of the first heart sound. When the ventricular rhythm is irregular due to atrial fibrillation, the intensity of the sound is inversely proportional to the length of the preceding diastolic interval. When the sound of tricuspid closure is accentuated, it may be identified by auscultation as the initial component of a split first sound mesial to the apex. Measurement of the interval from the onset of the QRS complex of the electrocardiogram to the "first heart sound" should be made to the mitral component of the first sound when this can he identified on the phonocardiogram.