Differential Diagnosis

A. Innocent Murmurs. Refers to murmurs that are not associated with any underlying structural heard disease (ie, heart is anatomically normal). These sounds are considered nonpathologic and physiologic. Patients with innocent murmurs do not require bacterial endocarditis precautions.

1. Peripheral pulmonic stenosis. Common systolic murmur of neonates, typically heard over pulmonic area (left second intercostal space), with wide radiation to back and into axillae bilaterally. Reflects the more acute angle of origin of branch pulmonary arteries from the main pulmonary artery. Rarely persists beyond 3-6 months of age.

2. Still's murmur. Common systolic murmur of childhood, rare in neonates. Typically grade 2-3/6, heard over the left lower sternal border and cardiac apex, and louder in supine posture. Distinguished by characteristic vibratory, honking, or twanging-quality overtone. This murmur, as with other innocent murmurs, may be accentuated with fever or increased cardiac output.

3. Venous hum. The only innocent continuous murmur; reflects the sound of normal systemic venous return through jugular veins. Diastolic component is louder, distinguishing it from arterial continuous murmurs. Heard at the right infraclavicular area in children in the sitting position; changes with head turning maneuvers, and eliminated by compression over jugular vein. 4. Pulmonary flow murmur. A systolic ejection murmur, heard over the pulmonic area. There is no click, as would be heard in valvar pulmonic stenosis, and the second heart sound (S2) is normally split. Exaggerated in older patients with absent thoracic kyphosis (straight back syndrome), which brings the pulmonary trunk closer to the anterior chest wall.

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