SAEVA Congress 2018 Proceedings | 12-15 February 2018 | ATKV Goudini Spa
is loudest, a ventricular septal defect (VSD) is most likely but if the left sided murmur is
loudest, a VSD in the outflow portion of the interventricular septum or complex
congenital heart disease should be suspected.
Ventricular Septal Defect
The membranous VSD is usually readily imaged with two-dimensional
echocardiography in horses. The visualization of the defect, combined with continuous
wave Doppler echocardiographic detection of the peak shunt velocity through the
defect is the technique of choice for diagnosing the VSD and determining its
significance in the horse. Inlet or membranous VSDs (the most common) are most
frequently imaged underneath the septal leaflet of the tricuspid valve and the
noncoronary or right coronary cusp of the aortic valve. The right parasternal LVOT long
axis view is the best view in which to image the membranous VSD.
VSD LVOT view
The size of the ventricular septal defect should be measured in two mutually
perpendicular planes across the defect's largest diameter to obtain an estimate of the
defect's size. VSDs in the muscular and outflow portions of the interventricular septum
are often more difficult to detect.
One of the aortic valve cusps (usually the noncoronary or the right coronary cusp) may
prolapse into the VSD, resulting in mild AR. Left atrial and left ventricular volume
overload are usually detected. Right ventricular enlargement and volume overload are
also present in horses with larger perimembranous VSDs or large defects located in
the muscular portion of the interventricular septum. Pulmonary artery dilatation is
detected in horses with large VSDs.
Pulsed, color flow and continuous wave Doppler echocardiography are used to identify
the location of the VSD, determine shunt direction and the associated pressure
gradient, and map shunt flow and any associated regurgitation. Interventricular
pressure gradients should be noninvasively estimated with continuous wave Doppler
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