The Varying Clinical Spectrum of the Systolic Click-Late Systolic Murmur Syndrome

Striking auscultatory variations with changes in posture were observed in 30 individuals with either mid-late systolic clicks, late systolic murmurs, or both, particularly in the upright position. Twenty-seven patients had late systolic murmurs; in nine, however, the murmur was not heard until assumption of the sitting position. Mid-late systolic clicks were heard in 20 patients while supine and in three only on sitting. Click movement (usually toward the first sound) was common during sitting or standing. Late systolic murmurs became holosystolic in 25 patients. In 20, the murmur did not become holosystolic until standing. Systolic whoops, not heard in the supine position, developed on assumption of the sitting position (three patients) or standing (three patients). With prompt squatting, the auscultatory findings reverted to those heard in the supine position in eight of nine patients. All observations were confirmed with phonocardiograms. Structural alterations in the mitral valve complex resulting in systolic prolapse of leaflets into the left atrium occur in these patients. Posture related changes in mitral valve function most likely explain the auscultatory phenomena.