Still's functional vibratory murmur

Specialty: Pediatrics.

• Innocent still breath
• benign infantile heart murmur
• systolic vibratory murmur

Why it occurs

• Accelerated and turbulent blood flow through an anatomically normal left ventricular outflow tract (vibration is attributed to the chordae tendineae of the left ventricle or the aortic valve itself in hyperdynamic states)
• High fever or dehydration (states of high cardiac output that temporarily increase circulatory speed and murmur intensity)
• Childhood anemia (lower blood viscosity promotes turbulent flow and enhances functional murmurs)
• Strenuous physical activity or anxiety (sympathetic stimulation with tachycardia that increases the transvalvular pressure gradient)

Initial workup

The clinical diagnosis is made through a thorough physical examination. The classic Still's murmur is systolic ejection, of grade I-II/VI intensity, with vibratory or "musical" timbre, located at the low-middle left sternal border, which noticeably decreases in intensity or disappears completely when changing position from supine to standing. If there are clinical doubts or red flags: 12-lead electrocardiogram (ECG) (to rule out ventricular or atrial hypertrophy). Chest x-ray (to evaluate cardiac silhouette and pulmonary flow). Color Doppler echocardiogram (definitive study of choice to unequivocally rule out any structural heart disease such as atrial septal defect, ventricular septal defect or valvular stenosis).

Standard management

• No type of pharmacological treatment or bacterial endocarditis prophylaxis is required for innocent Still's murmur. If anemia is associated, treatment consists of the administration of ferrous sulfate — elemental iron at doses of 3-6 mg/kg/day orally
• Antipyretics such as Paracetamol (dose of 10-15 mg/kg orally) or Ibuprofen (dose of 10 mg/kg orally) to control fever, which will immediately reduce the hyperdynamic component and the intensity of the murmur.