A presystolic murmur, also called presystolic accentuation, is a type of
diastolic heart murmur
Diastolic heart murmurs are heart murmurs heard during diastole, i.e. they start at or after S2 (heart sound), S2 and end before or at S1 (heart sound), S1. Many involve stenosis of the Heart valve#Atrioventricular valves, atrioventricular valves ...
typically associated with the opening snap in
mitral valve stenosis
Mitral stenosis is a valvular heart disease characterized by the narrowing of the opening of the mitral valve of the heart. It is almost always caused by rheumatic valvular heart disease. Normally, the mitral valve is about 5 cm2 during d ...
. It is heard following the middiastolic rumble of the stenotic valve,
[Eric J. Topol]
The Topol Solution: Textbook of Cardiovascular Medicine
Third Edition with DVD, Plus Integrated Content Website, Volume 355. Lippincott Williams & Wilkins, Oct 19, 2006; page 222. during the
diastasis phase, making it a "late diastolic" murmur.
The murmur is heard due to antegrade flow of blood through a progressively narrowing mitral opening during the end of the
atrial systole
The cardiac cycle is the performance of the human heart from the beginning of one heartbeat to the beginning of the next. It consists of two periods: one during which the heart muscle relaxes and refills with blood, called diastole, following ...
. This antegrade flow through the mitral valve before it completely closes appears to be the result of a pressure gradient at the end of diastole.
As its name so indicates, the presystolic murmur is heard before the mitral valve produces the S1 heart sound.
Less often, a presystolic murmur can be heard when a right
atrial myxoma causes a tricuspid valve obstruction to blood flow.
References
Heart murmurs
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