What is the classic murmur of a ventricular septal defect (VSD)?

Classic Murmur of Ventricular Septal Defect (VSD)

The classic murmur of a ventricular septal defect (VSD) is a holosystolic (pansystolic) murmur best heard at the lower left sternal border. 1

Characteristics of the VSD Murmur

• Timing: Holosystolic (pansystolic), beginning with the first heart sound (S1) and continuing through systole to the second heart sound (S2) 1
• Location: Best heard at the lower left sternal border 1, 2
• Quality: Harsh, high-pitched 1
• Configuration: Plateau-shaped (uniform intensity throughout systole) rather than crescendo-decrescendo 1
• Radiation: May radiate across the precordium 1
• Intensity: Variable, depending on the size of the defect and pressure gradient between ventricles (typically grade 2-6/6) 1

Physiologic Basis

• The holosystolic murmur is generated by blood flow between chambers that have widely different pressures throughout systole (left ventricle to right ventricle) 1
• The pressure gradient and regurgitant jet begin early in contraction and last until relaxation is almost complete 1
• In large VSDs with pulmonary hypertension or small muscular VSDs, the shunting at the end of systole may be insignificant, resulting in an early or midsystolic murmur rather than the classic holosystolic murmur 1

Dynamic Auscultation Findings

• The intensity of the VSD murmur increases with:
  • Handgrip exercise 1
  • Transient arterial occlusion (bilateral arm cuff inflation) 1
• The murmur typically decreases during Valsalva maneuver 1
• Unlike semilunar valve murmurs, VSD murmurs do not increase in intensity following a premature ventricular beat 1

Associated Findings

• A palpable left parasternal heave may be present due to right ventricular volume overload 2
• Fixed splitting of the second heart sound may be present if there is associated atrial septal defect 1
• In patients with significant left-to-right shunting, signs of pulmonary overcirculation may be present 1
• Cardiomegaly may be evident on chest X-ray in moderate to large defects 2

Variations by VSD Type

• Perimembranous VSDs (most common, ~80% of cases) typically produce the classic holosystolic murmur 1, 3
• Muscular VSDs may have a more variable murmur, sometimes early or midsystolic rather than holosystolic 1
• Inlet VSDs (often associated with Down syndrome) also produce a holosystolic murmur 1

Clinical Pearls

• The murmur of VSD should be distinguished from mitral regurgitation, which is also holosystolic but typically loudest at the apex rather than the left sternal border 1
• In post-myocardial infarction VSDs, the murmur may rarely be continuous rather than just holosystolic 4, 5
• In patients with congenitally corrected transposition of the great arteries (CCTGA) who have an associated VSD, the holosystolic murmur will be similar to those with normal connections 1

Remember that while auscultation is valuable for initial diagnosis, echocardiography is essential for confirming the presence, size, location, and hemodynamic significance of a VSD 1, 6.