Congenital cardiac disease in dogs.

Ventricular septal defect (VSD) generally occurs high in the membranous septum rather than lower in the muscular portion. The English Bulldog and Siberian Husky may be predisposed. Clinical signs include a holosystolic or crescendo-decrescendo murmur best heard low on the right side at the 3rd-4th intercostal space and, with large defects, pulmonary congestion, exercise intolerance, cyanosis and ascites. The ECG is normal unless the right ventricle is hypertrophied, which causes right axis deviation and other electrocardiographic signs of right-sided heart enlargement. Plain film thoracic radiographs reveal signs of right-sided heart enlargement but often are not diagnostic. Nonselective angiocardiography is often not useful in diagnosing VSD with a left-to-right shunt of blood. Selective angiocardiography, in which contrast medium is injected directly into the left ventricle via a catheter, is the method of choice for diagnosis of VSD. Dogs with a small VSD remain asymptomatic, but those with large defects require surgical correction with a prosthetic septal pathic or pulmonary artery band.