Hemodynamic-Phonocardiographic Correlations of the Fourth Heart Sound in Aortic Stenosis

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Abstract
The hemodynamic findings obtained at left heart catheterization in 46 patients with aortic stenosis of varying severity were correlated with the presence of a fourth heart sound determined phonocardiographically. From this correlation it may be concluded that, when a fourth heart sound is detectable in an adult patient with aortic stenosis, it usually indicates that the obstruction is severe (gradient exceeding 70 mm. Hg, left ventricular systolic pressure above 160 mm. Hg), that the left ventricular end-diastolic pressure is elevated (12 mm. Hg or above), and that the "a" wave in the left atrial pressure pulse is tall (14 mm. Hg or higher). The sound probably results from a forceful atrial contraction that forces a large volume of blood into a ventricle, the walls of which have been rendered less compliant than normal by the presence of left ventricular hypertrophy. The presence of this sound is easily detectable at the bedside by auscultation, and its presence may be confirmed by phonocardiography. The potential clinical usefulness of this physical finding, the presence of which is capable of separating patients with moderate or severe obstruction from those with mild obstruction, is self-evident.