Cardiology > Functional Murmurs

   Background

Functional murmurs (also called innocent or physiologic murmurs) are non-pathologic heart sounds resulting from normal blood flow dynamics through the heart or great vessels. They occur in the absence of structural cardiac abnormalities and are most commonly found in children, adolescents, pregnant women, and hyperdynamic states. 

II) Classification or Types 

By Age Group: 

• • Still’s Murmur: Common in children; musical or vibratory systolic murmur best heard at the left lower sternal border. 

• • Pulmonary Flow Murmur: High-pitched systolic murmur in adolescents or adults, best heard at the left upper sternal border. 

• • Venous Hum: Continuous murmur heard over the upper chest or neck due to jugular venous flow. 

• • Supraclavicular Systolic Murmur: Common in healthy children and young adults; due to blood flow in the subclavian or brachiocephalic artery. 

• • Mammary Souffle: Systolic-diastolic murmur heard during pregnancy or lactation, due to increased blood flow through the mammary arteries. 

By Physiologic State: 

• • Hyperdynamic states (fever, anemia, thyrotoxicosis, anxiety, exercise, pregnancy) 

By Timing: 

• Systolic (most common) 

• Diastolic (rare; typically pathologic if present) 

• Continuous (e.g., venous hum) 

III) Epidemiology 

• • Sex: Occurs equally in males and females. 

• • Age: Most prevalent in children (50–70%) and adolescents; less common in adults. 

• • Geography: Globally prevalent. 

• • Comorbidities: Usually none; associated with increased cardiac output in certain physiologic states. 

  Etiology

I) What Causes It 

• • High flow states across structurally normal valves: 

• • Fever 

• • Exercise 

• • Pregnancy 

• • Anemia 

• • Thyrotoxicosis 

• • Anxiety 

• • Physiologic flow in developing cardiovascular systems (children) 

II) Risk Factors 

• • Age (childhood or adolescence) 

• • Febrile illness 

• • Hyperthyroidism 

• • Anemia 

• • Pregnancy 

• • Anxiety or heightened sympathetic tone 

   Clinical Presentation

I) History (Symptoms) 

• • Asymptomatic 

• • No associated fatigue, dyspnea, syncope, or chest pain 

• • Found incidentally during routine examination 

II) Physical Exam (Signs) 

Vital Signs: 

• • Normal; occasionally mild tachycardia in high-output states 

Cardiac Exam: 

• • Soft, low-grade systolic murmur (grade I–II/VI) 

• • Best heard at left sternal border or pulmonary area 

• • Varies with position (often disappears when supine) 

• • No radiation, thrills, clicks, or gallops 

• • Normal S1 and S2 

• • No heaves or displaced PMI 

Pulmonary and Peripheral: 

• • Normal respiratory sounds 

• • No edema, cyanosis, or clubbing 

  Differential Diagnosis (DDx)

• • Pathologic murmurs: 

• • Aortic stenosis 

• • Pulmonary stenosis 

• • Hypertrophic cardiomyopathy 

• • Ventricular septal defect 

• • Mitral valve prolapse 

• • Atrial septal defect 

• • High-output states: 

• • Anemia 

• • Fever 

• • Hyperthyroidism 

• • Pregnancy 

   Diagnostic Tests

Initial Assessment: 

• • Clinical evaluation is paramount; often sufficient to distinguish innocent from pathologic murmurs. 

Further Evaluation (if murmur is atypical or exam unclear): 

• • Transthoracic Echocardiogram (TTE): 

• • Confirms normal cardiac anatomy and function 

• • Used when murmur characteristics suggest potential structural abnormality 

• • ECG: 

• • Normal in innocent murmurs 

• • Rule out arrhythmias or chamber enlargement 

• • Chest X-ray: 

• • Normal cardiac silhouette and pulmonary vasculature 

• • CBC, TSH (if systemic cause suspected): 

• • Anemia or thyrotoxicosis 

   Treatment

I) Medical Management: 

• • No treatment required for innocent murmurs 

• • Address underlying cause in high-output states: 

• • Antipyretics for fever 

• • Iron supplementation for anemia 

• • Beta-blockers or antithyroid drugs for hyperthyroidism 

II) Interventional/Surgical: 

• • Not indicated for functional murmurs 

• • Reassure patient and family 
    
    
    

 Patient Education, Screening,
Vaccines

• • Explain benign nature of the murmur 

• • Emphasize no restriction on activity or sports (if confirmed as functional) 

• • Educate about signs of pathologic murmurs (e.g., cyanosis, fatigue, syncope) 

• • Screen for anemia, thyroid disease if suspected 

• • Routine vaccinations as per age/guidelines 

  Consults

• • Pediatric/Cardiology consult: 

• • Murmur > grade III 

• • Diastolic murmur 

• • Associated symptoms (e.g., cyanosis, exertional syncope) 

• • Murmur that increases with standing or Valsalva 

• • Abnormal ECG or CXR findings 

• • Primary Care: 

• • Routine monitoring in asymptomatic patients 

   Follow-Up

• • None required for confirmed innocent murmurs 

• • Annual physical exams with auscultation 

• • Follow-up echocardiogram only if murmur characteristics change 

• • Monitor for any emerging symptoms or clinical changes