ASD vs. VSD Murmur Difference

ASD (Atrial Septal Defect)

• Wide, Fixed split S2 (in contrast to the normal variation in splitting during the respiratory cycle).
• Most commonly, a soft pulmonary ejection murmur (systolic flow murmur) can be heard over the 2nd LEFT intercostal space.
• There can accompanying diastolic rumble due to increased flow over the tricuspid valve.
• NOTE: The murmur generated is not from the flow through the defect. WHY? The shunt flow across the ASD has too low a velocity and produces too little turbulence to be audible.

VSD (Ventricular Septal Defect)

• Holosystolic murmur (continuous left-to-right shunt) at 3-4th intercostal space with a thrill (vibratory sensation felt on the skin overlying the heart, which indicates turbulence)
• NOTE: Smaller defects generate louder murmurs due to more turbulence!

References

1. Bradley EA, Zaidi AN. Atrial Septal Defect. Cardiol Clin. 2020 Aug;38(3):317-324.
2. Spicer DE, Hsu HH, Co-Vu J, Anderson RH, Fricker FJ. Ventricular septal defect. Orphanet J Rare Dis. 2014 Dec 19;9:144.