A presystolic murmur, also called presystolic accentuation, is a type of diastolic heart murmur typically associated with the opening snap in mitral valve stenosis. It is heard following the middiastolic rumble of the stenotic valve, during the diastasis phase, making it a "late diastolic" murmur. Less often, a presystolic murmur can be heard when a right atrial myxoma causes a tricuspid valve obstruction to blood flow.