Systolic honks in young children.

Three children with loud systolic honks were studied noninvasively with phonocardiography and echocardiography. It was shown that the precordial honk, like the late systolic mitral murmur and the clicking apical systolic sound, is part of a continuum of auscultatory sounds that result from a defect of mitral valve support and are classified under the general heading of mitral valve prolapse syndrome. Prolapse of one or both of the mitral valve leaflets is believed to cause the characteristic auscultatory findings of click, murmur or honk. The timing of these sounds in systole varies with different physiologic or pharmacologic maneuvers. Variations in the onset of prolapse are associated with changes in left ventricular end-diastolic dimensions.