Heart murmurs are common in the first days of life and do not usually signify structural heart problems. If a murmur is present at birth, however, it should be considered a valvular problem until proved otherwise because the common benign transitional murmurs (eg, patent ductus arteriosus) are not audible until minutes to hours after birth.

If an infant is pink, well-perfused, and in no respiratory distress and has palpable and symmetrical pulses (right brachial pulse no stronger than the femoral pulse), the murmur is most likely transitional. Transitional murmurs are soft (grade 1–3/6), heard at the left upper to midsternal border, and generally loudest during the first 24 hours. If the murmur persists beyond 24 hours, blood pressure in the right arm and a leg should be determined. If there is a difference of more than 15 mm Hg (arm > leg) or if the pulses in the lower extremities are difficult to appreciate, cardiology consultation should be arranged.

One way of thinking about innocent murmurs is to consider the vascular system as a series of tubes and compartments that are joined to each other. At these junctions there can be a normal degree of turbulence as the blood traverses from one tube or chamber to the next. This normal turbulence can set the surrounding tissues into vibration and this vibration is transmitted out through the chest and to the stethoscope. Types of innocent murmurs include:

Venous Hum


Following the course of the blood, we can first discuss the normal and positional low- pitched continuous rumble of the blood draining through the jugular veins and the superior vena cava into the right atrium. This murmur disappears with turning of the head or change from the sitting to supine position.


Pulmonary Flow Murmur

Next, the blood may be mildly turbulent as it flows from the right ventricular out flow tract across a normal pulmonary valve and into a rapidly growing main pulmonary artery or branched pulmonary artery. This pulmonary flow type murmur is common in infants, has a medium pitch, a soft 2/6 intensity and is heard best along the left upper sternal border. It generally does not radiate well through out the back. Importantly, this innocent murmur is not usually associated with an early systolic ejection click (but mild pulmonary artery stenosis may.) When the diagnosis of benign pulmonary flow type murmur is made, extra care must be taken to ensure that there is a normal physiologic split of the second heart sound with respiration, and that the precordial activity is normal (absence of right ventricular prominent lift).

Peripheral Pulmonary Artery Stenosis Murmur

In the first two months of age, it is common to have a mild degree of turbulence at the branch point from the main pulmonary artery to each of the branched pulmonary arteries. This innocent murmur of mild branched pulmonary artery turbulence (also termed mild peripheral pulmonary artery turbulence) has a medium pitch and radiates though out the precordium with specific radiation to the axillae. The blood then traverses the lungs and returns to the left atrium and left ventricle. As the ventricle squeezes, blood is ejected though the left ventricular out flow tract past the aortic valve to the aorta.

Still’s Murmur

The flow of blood within the left ventricle may set in vibration support tissue within the left ventricle (left ventricular muscle cords) or the support structures to the mitral valve near the left ventricular out flow tract, such as the cordae and papillary muscle attachments to the left ventricle. This causes a soft grade 2/6 crescendo-decrescendo (ejection) type murmur with a medium pitch (relatively pure uniform frequency of 70- 130 cycles per second) and a characteristic musical vibratory quality “like plucking a taught piece of string under water”. This is the “Still’s-Murmur (George F. Still 1909) ” and is frequently also termed a benign ventricular ejection type murmur.

Supraclavicular Arterial Bruit Murmur

Innocent flow murmurs which are related to mild turbulence across a normal aortic valve radiate slightly to the right upper sternal border, are not associated with an ejection click, are crescendo-decrescendo and systolic, have a non-harsh quality and are termed the murmur of aortic bruit.

Finally, blood turbulence across normal aortic branches to the arms and head (brachiocephalic systolic murmur or supra- clavicular systolic murmur), or chest (mammary souffle) may cause innocent murmurs.

Source: Rain.com, Wikipedia.org, and Babycare Blog