An opening snap is a high pitched and sharp sound that is heard in early diastole, which is the phase of the cardiac cycle when your heart ventricles are filling up with blood.
The opening snap is often associated with the forceful opening of a stenotic "narrowed", but mobile mitral valve and is a key finding in diagnosing mitral stenosis.
The cause of the opening snap is when the mitral valve, which is typically narrowed or thickened due to conditions such as rheumatic heart disease, opens up suddenly.
The second heart sound-opening snap interval may be up to 12 hundredths of a second.
And the opening snap is also associated with a loud first sound and the diastolic murmur of mitral stenosis.
The difference between an opening snap and an ejection click is that an opening snap is a diastolic heart sound caused by the sudden opening of a stenotic mitral valve in early diastole.
An ejection click on the other hand is a systolic heart sound occurring early in systole and is also often associated with aortic stenosis or pulmonary stenosis.
The main difference is their timing within the cardiac cycle: opening snap is in diastole, while ejection click is in systole.