Systolic Murmurs

Heart murmurs have been classified in many ways, one of which is based on the timing of the murmur. Systolic murmurs have been divided into four types.

Midsystolic – occurs after S1 and before S2. This murmur usually has a shape of a crescendo/decrescendo pattern. It builds up to a max. intensity and then degrades. It has also been called a diamond shaped murmur or an ejection type systolic murmur b/c most of these murmurs are in fact ejection murmurs; they represent blood flow out of the aorta or out of the pulmonary artery. However, other valvular abnormalities can produce crescendo/decrescendo murmurs so that it is not particularly useful to call something an ejection murmur when it may not be. It’s best to call it a midsystolic murmur. This is the most common type of murmur that is appreciated clinically. It can represent a normal state, a so called innocent or benign murmur, simply due to increased velocity of blood flow or it can represent a structural abnormality of the heart.

Holosystolic (Pansystolic) – The second most common type of murmur. These begin with S1 and end with S2. If they originate in the left side of the heart they end with aortic closure. If they originate in the right side of the heart, they end with pulmonic closure. These murmurs remain relatively constant in intensity. They usually represent murmurs of AV (atrioventricular)valve regurgitation i.e. mitral or tricuspid insufficiency. They may also occur in ventricular septal defects or other congenital heart defects, but they are typically murmurs of AV valve regurgitation.

Early Systolic – Rare event. Begins with S1 and is a decrescendo murmur ending before S2. Usually occurs in one or two very different settings. It occurs in individuals with ventricular septal defects that are small and are physiologically closing. That is, as systole continues, there’s a gradient btwn. the left and right ventricles, hence a murmur is generated due to velocity. As the defect becomes smaller with systole (if it is a muscular VSD vs. a membranous VSD), you get a decrescendo murmur. Paradoxically, you can also hear these murmurs in the opposite extreme case, the so called Eisenmenger syndrome, where you have right sided pressures at systemic levels (almost equal pressure in RV and LV). During systole, these murmurs can abate simply b/c of equalization of pressures in the RV and LV. This is an extreme end- stage condition in patients with large VSDs.

Late Systolic – Also rare. Begins after S1 and goes into S2. This is the murmur of mitral valve prolapse that occurs due to a valve becoming incompetent during systole and allowing a gradient of pressure btwn the LV and LA until the end of systole.

Category: Cardiology Notes