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(Circulation. 1961;24:180.)
© 1961 American Heart Association, Inc.

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The Mechanism of Respiratory Variation in Splitting of the Second Heart Sound

ROBERT F. CASTLE M.D.¹ KENNETH L. JONES B.A.¹

¹ From the Department of Pediatrics, Duke University School of Medicine, Durham, North Carolina.

This study of 68 normal children has shown that in the supine position and under conditions of normal respiration splitting of the second sound averages .02 second in expiration and .04 second in inspiration. Inspiratory increase in splitting of the second sound is the result not only of a delay in pulmonic valve closure but also of earlier aortic closure. Movement of the aortic component is responsible, on the average, for 35 per cent of the difference in splitting of the second sound in inspiration and expiration.

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				V. R. Pilapil and D. P. Zipes Small Atrial Septal Defect associated with Physiologic Splitting of the Second Heart Sound: Difficulty in Diagnosis Without Cardiac Catheterization Clinical Pediatrics, January 1, 1971; 10(1): 18 - 22. [Abstract] [PDF]