The graphic registration of heart sounds and murmurs (phonocardiography) has greatly facilitated analysis of their pattern, timing, and relation to hemodynamics. Many of the principles and facts so established are being applied to auscultation with great benefit to that art.
Systolic murmurs fall into 2 main groups, ejection murmurs and regurgitant murmurs, according to their shape and relation to the heart sounds.
Ejection systolic murmurs are separated from the first heart sound by the isometric contraction time; they are crescendo-diminuendo in pattern (diamond shaped) and finish appreciably before the second heart sound. They are due to ejection of blood from the left or right ventricle into the aorta or pulmonary artery when there is stenosis of the appropriate valve or outflow tract, valve disease without stenosis, or—without valve disease-increased forward stroke flow or dilatation of the aorta or pulmonary artery. Small ejection vibrations can be recorded in normal subjects and their physiologic accentuation is probably responsible for most systolic murmurs that prove to be innocent.
Regurgitant systolic murmurs are pansystolic for they start with the first heart sound and finish with the second; the volume of sound emitted is relatively constant throughout systole or increased in late systole. They are caused by backflow of blood through the mitral or tricuspid valve or by a left-to-right shunt of high velocity through a ventricular septal defect or patent ductus arteriosus.
- © 1958 American Heart Association, Inc.