Ventricular septal defect – perimembranous

Perimembranous ventricular septal defect (VSD)

Perimembranous ventricular septal defect (VSD)
Perimembranous ventricular septal defect (VSD)

Medium sized ventricular septal defect in peri-membranous location seen from the apical five chamber view. RV: right ventricle; LV: left ventricle; VSD: ventricular septal defect; Ao: aorta; RA: right atrium; LA: left atrium; IVS: interventricular septum. There is aneurysm of the interventricular septum covering the VSD, leaving a small gap. The VSD jet passes through this small defect which is restrictive (below). Interventricular septal aneurysm formation is one method of spontaneous closure of ventricular septal defects. Sometimes the septal leaflet of the tricuspid valve can get attached at the rim of the VSD leading to partial closure, but leading to tricuspid regurgitation. Alternate method of spontaneous closure is by prolapse of the aortic valve, although at the expense of producing aortic regurgitation. Apical five chamber view includes LV, LA, RA, RV and proximal aorta as the fifth ‘chamber’. The view is obtained by tilting the transducer slightly after obtaining an apical four chamber view from the cardiac apex.

VSD Jet on continuous wave Doppler
VSD Jet on continuous wave Doppler

VSD jet documented by continuous wave Doppler interrogation, showing an interventricular gradient of 61.5 mm Hg, which suggests that the defect is restrictive. Actual gradient may be even more as this jet has an incomplete envelope. Correct alignment of the jet parallel to the ultrasound beam is needed to measure the actual jet. If the alignment angle is more than 20 degrees, the gradient will be grossly underestimated. Modern echocardiographs incorporate angle correction algorithms to estimate the true jet velocity if there is significant angle between the jet and the Doppler beam. But this facility should be used cautiously as unphysiological values may be obtained for higher degrees of angle correction.

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