What are the non organic causes of cardiac murmur?

Non organic causes of cardiac murmurs are innocent murmurs, hemic murmurs and functional murmurs.

1.Innocent murmur

1. Also called as stills murmur
2. Commonly occur in children, disappear as the child grows.
3. Here heart and its valves are normal and resting cardiac output is also normal.
4. They are the most common cause of murmur

Mechanism of innocent murmur

1. Innocent murmur is produced due to following
2. In children there is hyperkinetic circulation due to increased heart rate
3. Increased resistance in pulmonary vascular bed.

What are the features of innocent murmur

1. They are localised systolic murmurs
2. Best heard over the pulmonary area
3. Better heard in supine position, murmur disappear in upright position
4. Murmur better heard after exercise, fever and crying
5. Heart sounds are normal, there is no thrill.

2.Physiologic murmur

1. When the murmur is related to increased cardiac output they are called physiologic murmur.
2. Here there is no organic disease.
3. They occur due to rapid early ejection of blood into aorta producing turbulence.
4. They are short systolic murmurs best heard in 2-4left intercostals space.
5. No radiation of murmur
6. Standing increases the physiologic murmurs

3.Haemic murmur

1. In patients with severe anemia an ejection systolic murmur may be heard in pulmonary area.
2. They are produced due to increased blood flow through the pulmonary artery and dilatation of pulmonary artery.
3. Correction of anemia result in disappearance of murmur.
4. Sometimes you may get a systolic thrill.

4.Functional murmur / flow murmur

1. At the site of production of murmur there is no organic heart disease.
2. Murmur is produced due to increased blood flow across the valve

Examples are 

1. Systolic mumur in pulmonary area in atrial septal defect (ASD)
2. Graham steel murmur of functional pulmonary incompetence
3. Functional aortic stenotic systolic murmur in AR (Aortic regurgitation)
4. Apical mid-diastolic murmur in AR (Austin flintic murmur)

Features of flow murmur 

1. Usually 
2. Localised
3. Systolic
4. Soft murmur
5. No significant postural change in murmur
6. Usually there is no thrill (Thrill may sometimes present)
7. There is no cardiomegaly
8. 2nd heart sound normal
9. Murmur disappear after the correction of increased flow