What are the characteristic heart sounds in patients with Tetralogy of Fallot (TOF)?

Characteristic Heart Sounds in Tetralogy of Fallot

Unoperated/Pre-Repair Patients

In unoperated patients with Tetralogy of Fallot, the hallmark finding is a loud precordial systolic ejection murmur from right ventricular outflow tract obstruction, which can be mistaken for a small VSD. 1

• Loud systolic ejection murmur is heard along the left sternal border, reflecting the degree of right ventricular outflow tract obstruction 1
• The murmur intensity is inversely related to cyanosis severity - more severe obstruction produces less flow across the RVOT, resulting in a softer murmur and more cyanosis 1
• Patients with severe obstruction and abundant aorticopulmonary collaterals may present with loud continuous murmurs over the thorax 1
• In "pink tetralogy" (mild pulmonary obstruction), the loud precordial murmur often leads to misdiagnosis as an isolated VSD 1

Post-Repair Patients

The typical post-repair patient has a soft ejection systolic murmur from the RVOT, with an absent P2 component of the second heart sound being the most consistent finding. 1

Primary Auscultatory Findings:

• Soft ejection systolic murmur from the right ventricular outflow tract is the most common finding 1
• Absent P2 component of the second heart sound is characteristic and reflects pulmonary valve disruption or absence 1
• Low-pitched, delayed diastolic murmur in the pulmonary area indicates pulmonary regurgitation, which is nearly universal after transannular patch repair 1

Additional Murmurs to Assess:

• Pansystolic murmur suggests a residual VSD or VSD patch leak 1
• Diastolic murmur of aortic regurgitation may be present, particularly with aortic root dilation 1
• Tricuspid regurgitation murmur can develop secondary to right ventricular dilation 2

Patients with Prior Palliative Shunts:

• Continuous murmur indicates a patent systemic-to-pulmonary shunt (e.g., Blalock-Taussig shunt) 1
• Cyanosis and clubbing are typically present in shunt-only patients 1
• Diminished or absent brachial and radial pulses on the side of a classic Blalock-Taussig shunt 1

Clinical Correlation

The absence or presence of specific heart sounds provides critical hemodynamic information:

• Absent P2 with diastolic murmur strongly suggests significant pulmonary regurgitation leading to RV volume overload 1
• Loud systolic murmur with preserved P2 may indicate residual or recurrent RVOT obstruction requiring intervention 1, 2
• New or worsening murmurs in previously stable patients warrant comprehensive echocardiographic reassessment 2

Important Pitfalls

• Do not confuse the soft post-repair RVOT murmur with significant residual obstruction - echocardiography is required for accurate gradient assessment 1
• The severity of pulmonary regurgitation is often underestimated by auscultation compared to Doppler echocardiography 1
• Absence of an audible diastolic murmur does not exclude significant pulmonary regurgitation, as 87% of post-valvotomy patients have PR on Doppler despite only 58% having an audible murmur 1
• A loud P2 is NOT expected in repaired TOF and should prompt evaluation for pulmonary hypertension from alternative causes 3