SN7
SHORT NOTE
5M
Define Innocent (Functional) Murmurs. Describe its types and management.
Definition
- An innocent (functional or physiological) murmur is a heart murmur that occurs in the absence of any structural cardiac abnormality.
- Such murmurs are very common — heard in up to 50% of normal children at some time — and are benign.
Characteristics (the '7 S'S of an Innocent Murmur')
- Soft (grade ≤ 2/6) and Systolic (never purely diastolic).
- Short duration; Sensitive (varies with position/respiration).
- Single (no added sounds), with a Small area of radiation and a Sweet (soft, musical) quality.
- Normal S2; no thrill, no symptoms, and a normal ECG/X-ray.
Common Types
- Still's murmur — a low-pitched, vibratory/musical systolic murmur at the lower left sternal border (the commonest).
- Venous hum — a continuous murmur below the clavicle that disappears on lying down or turning the head.
- Pulmonary flow murmur — a soft ejection systolic murmur in the pulmonary area.
Features Suggesting a Pathological (not Innocent) Murmur
- A loud (grade ≥ 3) murmur, a thrill, or a diastolic murmur.
- An abnormal second heart sound, added sounds, or radiation.
- Symptoms (cyanosis, breathlessness, poor feeding, failure to thrive) or abnormal pulses/ECG/X-ray.
Management
An innocent murmur needs no treatment and usually no investigation — only reassurance of the family. If any pathological feature is present, echocardiography and cardiology referral are indicated.
WHY They Occur
Innocent murmurs arise from normal turbulent blood flow across normal structures, and are commoner during fever, anaemia or exercise (high-output states) — they may disappear when the child is well and calm.
Approach
- A careful history and examination usually distinguish innocent from pathological murmurs.
- If all features are reassuring, only reassurance is needed; any concerning feature warrants echocardiography.
When to Refer
- Any murmur that is loud (≥ grade 3), diastolic, or accompanied by a thrill.
- An abnormal S2, added sounds, abnormal pulses, cyanosis, or symptoms (poor feeding, breathlessness, failure to thrive).
- Diagnostic uncertainty — echocardiography settles the question.
Never diastolic — any diastolic murmur is pathological.
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