What percentage of congenital heart diseases do not present with a murmur?

Percentage of Congenital Heart Diseases Without Murmur

Approximately 10-25% of congenital heart diseases do not present with a heart murmur, making clinical detection challenging and potentially leading to delayed diagnosis into adulthood.

Epidemiology and Detection Challenges

Congenital heart disease (CHD) occurs in approximately 0.4% to 1% of live births 1, making it the most common type of congenital anomaly. While heart murmurs are a classic finding in many CHDs, a significant proportion lack this clinical sign:

• In a recent study of adults with CHD diagnosed in adulthood, 26.5% of all CHD cases were not detected until adulthood 2
• Many of these patients were asymptomatic or had nonspecific symptoms that didn't prompt cardiac evaluation earlier in life
• The absence of murmurs contributes significantly to delayed diagnosis

Types of CHD Most Likely to Present Without Murmurs

Certain congenital heart defects are more likely to be "silent" (without audible murmurs):

1. Atrial Septal Defects (ASDs):

   • Often asymptomatic until adulthood
   • May have subtle or no murmur despite significant shunting
   • Represent 23.9% of CHDs diagnosed in adulthood 2

2. Partial Anomalous Pulmonary Venous Return:

   • Frequently missed in childhood due to absence of characteristic murmurs
   • Represents 18.3% of adult-diagnosed CHDs 2

3. Bicuspid Aortic Valve:

   • May not produce a murmur until stenosis or regurgitation develops
   • Accounts for 16.8% of CHDs diagnosed in adulthood 2

4. Coarctation of the Aorta:

   • Can be missed if the narrowing is mild or if collateral circulation develops
   • Represents 8.2% of adult-diagnosed CHDs 2

5. Ebstein's Anomaly:

   • May not present with a murmur in milder forms
   • Accounts for 5.6% of adult CHD diagnoses 2

Factors Contributing to Absence of Murmurs

Several physiological factors explain why some CHDs don't produce audible murmurs:

1. Pressure Gradients: Minimal pressure differences across defects don't generate turbulent flow necessary for murmurs

2. Size of Defects: Very small or very large defects may not produce audible murmurs

   • Small defects: Insufficient flow disturbance
   • Large defects: May equalize pressures, reducing turbulence

3. Location of Defects: Some anatomical positions are less likely to produce audible murmurs

4. Pulmonary Hypertension: When pulmonary pressures approach systemic levels, the pressure gradient across septal defects decreases, potentially eliminating murmurs

Diagnostic Implications

The absence of murmurs has significant implications for CHD detection:

• Approximately 10% of common CHDs survive undetected until adulthood 1
• In patients with congenitally corrected transposition of the great arteries (CCTGA), those without associated lesions may not have characteristic murmurs 1
• Among patients diagnosed in adulthood, 47.4% already had complications at diagnosis, with pulmonary hypertension being most common (24.3%) 2

Diagnostic Approach When Murmurs Are Absent

For suspected CHD without murmurs, a multimodality imaging approach is essential:

1. Transthoracic Echocardiography (TTE):

   • First-line imaging modality
   • Can be used as the sole diagnostic tool in approximately 81% of pediatric CHD cases 3

2. Advanced Imaging:

   • Cardiac MRI: Excellent for extracardiac anatomy (76% diagnostic yield) 4
   • Transesophageal Echocardiography (TEE): Superior for intracardiac anatomy (71% diagnostic yield) 4
   • Combined MRI and TEE: Provides comprehensive assessment (80% diagnostic yield) 4

Clinical Vigilance

Given the significant percentage of CHDs without murmurs, clinicians should maintain a high index of suspicion in patients with:

• Unexplained dyspnea or exercise intolerance
• Arrhythmias of unclear etiology
• Pulmonary hypertension
• Family history of CHD
• Abnormal ECG or chest X-ray findings

The absence of a murmur should never exclude CHD from the differential diagnosis when other clinical features suggest its possibility.