What does the sounds lubb-dup mean in a cardiac cycle?


The period between the end of one heart beat to the end of the next heart beat is called a cardiac cycle. The cardiac cycle is formed of three phases

  • Atrial systole
  • Ventricular systole and
  • Joint diastole

When are the sounds “LUBB” and “DUP” produced respectively during heart beat?

The first sound “LUBB” is produced when the atrio-ventricular (tricuspid and bicuspid) valves get closed sharply at the start of ventricular systole. The second sound “DUP” is produced when at the beginning of ventricular diastole, the semilunar valves at the roots of aorta and pulmonary artery get closed.

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