Diastolic Murmurs

There are three types of diastolic murmurs

1. Early Diastolic Murmur (EDM). These are the most common type. It is a decrescendo murmur initiated by the (incomplete) closure of the aortic (or pulmonary on the right) valve. This is a high frequency murmur because of the high pressure gradient between the aorta and the left ventricle during diastole. This high frequency is unique among diastolic murmurs. To refresh your memory, the high frequency sounds kind of like the shooshing of Darth Vader breathing. Since the blood is flowing from the aorta back into the left ventricle you would listen for this along the lower left sternal border. They are best heard with patient sitting up, leaning forward, in held expiration. He did not say what it would sound like on the right.

2. Mid Diastolic Murmur (MDM). These tend to be low frequency sounds that develop as blood flows through the A/V valves. They are described as “rumbles”. They can be caused by either a restrictive valve (mitral stenosis) or sheer volume such a large left to right shunt. In this case, so much blood (the normal atrial return plus the added volume from the previous systole) is flowing over the tricuspid it causes a rumble. As you can guess, the same type of rumble will develop over the mitral valve in severe, chronic mitral regurgitation.

3. Pre-Systolic Murmurs. It would be too sensible to call these late diastolic murmurs, but know that that is essentially what they are. These are murmurs that run into the first heart sound. Early closure of the mitral valve during severe aortic regurgitation will show this (the murmur runs into S1 here because the murmur is basically causing S1 if the flow is big enough).

4. Continuous Murmurs. The definition of this is a little tricky. The murmur does not have to be constantly present to be termed continuous. It is a continuous murmur if it can be heard during systole and diastole. If it runs through S2, it is a continuous murmur. It is also to be distinguished from “to and fro” murmurs. These can appear to run through S2, but are actually two distinct murmurs, one of them ending at S2 while the other starts. An example of a to and fro murmur would be combined mitral regurgitation (systolic) and aortic regurgitation (diastolic). Continuous murmurs are rare and usually occur in the context of congenital heart disease. The typical one is caused by a patent ductus arteriosus. It produces a loud murmur in the second left intercostal space and will follow the pulmonary artery out toward the left lung. This can strange sounding if the murmur is loud enough to obscure S2.

Category: Cardiology Notes