Systolic murmurs which are best appreciated below the line of the second intercostal space near the sternum are likely to be holo-systolic type (regurgitant type) murmurs of atrio-ventricular valve (tricuspid or mitral valve) insufficiency or of ventricular septal defect.  Variations in pitch and location may help to differentiate the different murmurs of atrioventricular insufficiency.  Low to medium pitched murmurs along the lower left and right sternal borders are consistent with tricuspid insufficiency type murmurs.   The murmur is low pitched because the gradient between the peak right ventricular pressure and the right atrial pressure is usually less that 40mmHg (unless there are associated conditions such as pulmonic stenosis, elevated pulmonary vascular resistance or large ventricular septal defect.)   In contrast, the holo-systolic murmur of mitral insufficiency is usually best heard laterally at the apex of the heart with the patient in the left lateral decubitus position.  Mitral insufficiency has a high pitch because the gradient between the left ventricle and the left atrium is usually greater than 60-80mmHg during most of systole.  Because the left atrium is posterior to the left ventricle, the murmur of mitral insufficiency radiates posteriorly to the back.  The murmur of ventricular septal defect is usually heard below the line of the second intercostal space and is also usually holo-systolic.   Because the right ventricle is anterior to the left ventricle, the murmur of ventricular septal defect with left to right shunt radiates anteriorly to the left middle sternal border and not to the back.  This radiation pattern can be used to separate this high pitched holo-systolic murmur of a VSD from the similar murmur of mitral insufficiency.  Small muscular ventricular septal defects may completely close during the later part of systole due to the ventricular squeeze and this causes an early systolic murmur with a whispy trail-off high pitched quality.  The pitch of the murmur with ventricular septal defect is related to the relative pressure difference (pressure gradient) between the left ventricle and right ventricle across the VSD.  The larger the pressure difference between the ventricles, the louder, more harsh and higher pitched the murmur will be.  In the newborn period prior to 2 weeks of age, the pulmonary vascular resistance is higher than it will likely be at 1 to 2 months of age.  This means that the pressure gradient between the left and right ventricles will be small and newborns with ventricular septal defect may not present with a significantly loud or harsh heart murmur until 1 to 4 weeks of age.  After the normal maturational decrease in pulmonary vascular resistance the size of the ventricular septal defect may be estimated by the intensity, quality    (degree of harshness) and pitch of the heart murmur.  Tiny ventricular septal defects are soft and high pitched.  Small to moderate VSDs may have a loud (3-4/6), harsh, high pitched murmur.  Defects with a moderate to large amount of interventricular shunting may have loud murmur with a medium pitch.  Large (non-restrictive) ventricular septal defects may have a soft, medium to low pitch murmur or perhaps no VSD murmur at all.