In this heart sound, a combination of a grade 4/6 harsh ejection type (crescendo) systolic murmur as well as a grade 4/6 diastolic decrescendo murmur (ausculted over the left heart base) is audible. These murmurs in a 4-year-old boxer with congenital aortic valve stenosis are caused by severe valvular stenosis and severe aortic insufficiency. The combination of a systolic murmur (due to aortic valve stenosis and obstruction) along with a diastolic murmur (due to the aortic valve being malformed and leaking during diastole) creates what is called a ‘to-fro’ murmur. Compare this sound to the continuous sound of a patent ductus arteriosus to appreciate the differences between them.