Historically, James Hope was one of the first physicians to recommend methods to recognize benign and innocent murmurs. In his 1942 textbook, Hope says “murmurs from these causes may easily be distinguished from that of valvular disease…” As the 20th century approached, it became more common knowledge among the medical community that healthy children and adolescents may have murmurs and gallops on physical exam that have no pathologic significance, especially in the asymptomatic patient. 
Murmurs are the most common reason for pediatric cardiologist referral and evaluation. There are reports that up to 72% of children will have a murmur at some point during childhood and adolescence, and of these, some may stay present until adulthood, while others will resolve with time.  The concern of many practitioners stems from the anxiety of misdiagnosing a benign murmur in the setting of congenital heart disease (CHD). 
The incidence of congenital heart disease in the general population is less than 1%, and of all the new murmurs referred to a pediatric cardiologist, less than 1% are a result of CHD. 
History and Physical
Evaluation and identification of benign heart murmurs can be done primarily by thorough medical history and focused physical exam.
Neonates and Infants
Conduct a perinatal, prenatal, as well as maternal history if paramount in the evaluation of newborns with heart murmurs.  Include:
- Maternal age, because advanced maternal age is associated with an increased risk of all heart defects.
- History of maternal infections, such as TORCH, with a special focus on rubella infection in the first trimester given its high association with patent ductus arteriosus (PDA), pulmonary valve abnormalities, peripheral pulmonary stenosis, and ventricular septal defects (VSD).
- Maternal diabetes mellitus is also of importance due to its association with asymmetric hypertrophic cardiomyopathy.
Postnatal history is just as important, and should focus on feeding difficulties (sweating while feeding), failure to thrive, cyanosis during feeding or activity, respiratory symptoms (tachypnea and increased work of breathing). 
Note that grade 2/6 and louder murmurs in the first 24 hours of life are more likely to have an underlying cardiac disease, while lower pitch murmurs in the first, second, or third day of life could be related to changes in pulmonary vascular resistance, a closing PDA, and/or physiological tricuspid regurgitation. 
The importance of pre-ductal and post-ductal oxygen saturation in newborns are also an important part of this initial evaluation as differences of less than 3% with overall normal saturations exclude many congenital cardiac pathologies. 
In older children and adolescents the above still holds true, however special attention to activity level should be paid. Any patient with a new murmur and decreased activity level, or worsening exercise tolerance (especially compared to peers), or complaints of shortness of breath, chest pain or syncope on exertion should raise major concerns for underlying cardiac pathology. 
When assessing exercise tolerance, it is important to do so with an age-appropriate approach. 
As with any other patient, it is always important to start the examination of a child who has a murmur by general inspection and not directly with auscultation. The examiner should pay close attention for any dysmorphic features, color changes, respiratory effort, or other congenital anomalies. 
Every patient should have a complete set of vital signs, including blood pressure (BP).  If there is already a concern for underlying cardiac disease, then 4-limb blood pressure would be highly recommended. Look for any discrepancies in upper and lower limb blood pressures as this could rule-out in aortic coarctation. Remember that lower limb BP is generally 10 to 20 mm Hg higher than upper limb, and if the upper limb BP is higher, then coarctation needs to be ruled out. 
Oxygen saturation is also important. Cyanotic heart lesions may not present at birth, especially ductal-dependent lesions or Tetralogy of Fallot. If intra/extra-cardiac shunting is suspected then upper and lower extremity pulse oximetry should be measured. 
Palpation of the distal pulses should always be done in cardiac patients.  The quality and timing of the pulses can be very important in physical finding associated with certain cardiac lesions. In benign murmurs, the clinicians should be able to feel equal and normal pulses throughout, keeping in mind that physiologically, the femoral pulses should be felt earlier than the brachial pulses in an otherwise normal patient.
Palpation of the chest is also important as it can give you information of cardiomegaly due to a displaced point of maximal impulse (PMI) or a hyperdynamic precordium.  Thrills are also important as they will help grade any murmurs (discussed later).
Lastly, palpation of the abdomen is crucial. The abdominal exam may give the examiner insight into the organs of the patient, for example, situs inversus as well as findings of congestive heart failure such as hepatomegaly. 
The auscultatory examination should always be done systematically. The 4 general areas of the cardiac exam (aortic, pulmonary, tricuspid, and mitral) should be examined first, followed by areas of radiation such as the neck, axilla, and back. 
Each heart sound should be assessed independently for any abnormalities, clicks, extra sounds, and finally the presence of murmurs.
Special note should be made to the following characteristics of any murmur:
Timing: Systolic versus diastolic. Note than holosystolic/pansystolic murmurs are most often associated with cardiac lesions such as VSD. Purely diastolic murmurs are by definition always pathologic until proven otherwise by echocardiogram or cardiac cath. 
Intensity: Grading scale of 1 to 6. Note that a specialist should evaluate any murmur with a grade higher than 3 and consider it pathologic until proven otherwise. 
- Grade 1 is a sound softer than the heart sounds
- Grade 2 is a sound as loud as the heart sounds
- Grade 3 is louder the heart sounds
- Grade 4 is a grade 3 sound plus presence of a palpable thrill
- Grade 5 is a very loud sound heard with stethoscope barely on the chest
- Grade 6 is a very loud sound heard with the stethoscope just off the surface of the chest 
Location: Location of the murmur on the chest by auscultatory regions mentioned above. The region where the murmur is heard the loudest should be specified here. 
Quality: Harsh, blowing, musical, and squeaky. Benign murmurs are most often blowing or musical in quality. 
Pitch: Low, Medium, or High. High pitched murmurs are most often pathologic. Most benign murmurs have a low-soft pitch vibratory quality. 
Radiation: Murmurs are often heard loudest at one region and softer in others. Areas to which murmurs radiate to should be of note. Specifically radiation to unilateral axillae like in mitral regurgitation, or radiation to neck as in aortic stenosis.  Some benign murmurs may also radiate like pulmonary flow murmurs which radiate to the back or peripheral pulmonary artery stenosis which radiate to bilateral axillary lines. 
Response to Maneuvers: Pathologic murmurs, especially those of valvular origin will not change in intensity with maneuvers.  Other pathologic murmurs such as that from hypertrophic cardiomyopathy may change, but that will not be discussed in this article.
Benign murmurs often do change significantly with position. Specifically of note is the stills/flow murmur which is loudest while the patient is supine given the decrease in afterload seen in this position.  Venous hum murmurs also change but in the opposite manner. Venous hums are best heard with the patient sitting up and will most often completely disappear with the patient in the supine position. 
One auscultatory finding to keep in mind is that of a flow murmur in the presence of a widely-fixed split S2. The wide-fixed split second heart sound is the most consistent finding of an ASD even without the presence of a systolic ejection murmur.
Types of Benign Murmurs
Systolic Ejection Murmurs
Stills Murmur 
- Most common; usually disappears by adolescence but can persist into adulthood
- Musical, soft, vibratory low-pitched systolic ejection murmur heard best over left lower sternal border and apex. Grade 1 to 3/6. Loudest when supine. No radiation.
Innocent Pulmonary Flow Murmur 
- Second most common,
- Soft, blowing, low-pitched systolic ejection murmur, grade 1 to 3/6, usually heard best over the left upper sternal border and may radiate to the back and axilla.
Peripheral Pulmonary Artery Stenosis 
- Most commonly in the first year of life, especially in premature babies
- Short, soft, mid-systolic ejection murmur, grade 1 to 2/6, heard best over right/left upper sternal border with radiation to the axilla.
Arterial Supraclavicular Murmur 
- Most commonly seen in late childhood and early adolescence
- Brief, low-pitched murmur, grade 1 to 3/6, best hear in supraclavicular fossa and may radiate to the neck.
Benign Continuous Murmurs
Venous Hum 
- Most common continuous benign murmur, most often seen between 2 to 8 years of life
- Soft, whirling, low-pitched murmur, grade 1 to 3/6, heard best in high right sternal border and the right infraclavicular area in the upright position. Murmur does not radiate, disappears completely when supine or when patient extends the neck and turns to the right.
Mammary Souffle 
- Least common, usually heard primarily in young adult women, especially when pregnant or lactating.
- Soft, blowing, high-pitched systolic murmur, grade 1 to 2/6, heard best over anterior chest, specifically over the breasts, softer when upright or with high stethoscope pressure.