Update on common congenital heart diseases in dogs and cats

The identification of congenital cardiac disease in dogs and cats is clinically important. Even when the disease is severe, most patients with the most common congenital heart diseases present free of overt clinical signs, and disease is detected incidentally during routine puppy and kitten examination. Cardiac auscultation forms the basis for identification of most congenital cardiac defects.

Murmur recognition by cardiac auscultation: innocent versus pathological Innocent murmurs (murmurs that are not associated with underlying cardiac pathology) are common in growing puppies and kittens. They may be related to physiologic anemia and hypoproteinemia associated with age, changes in cardiac geometry during growth, relative high heart rate, and other factors. Innocent murmurs are always low intensity (I–II/VI), early to mid-systolic, high frequency or musical in character, and located at the left parasternal region (often the heart base). Most innocent murmurs will disappear after 6 months of age, however innocent murmurs do continue to be recognized in some adults, which can pose a diagnostic dilemma.

Murmurs that persist through growth, murmurs of higher intensity, murmurs that have a diastolic component, or murmurs associated with other signs of cardiac disease warrant further investigation, even at young age. It is important to realize that there is not always a direct positive correlation between murmur intensity and severity of disease. Sometimes the opposite is even true (e.g., small ventricular septal defects produce loud murmurs while a large atrial septal defect will produce no or only a soft murmurs). Physical exam information should always be interpreted in conjunction with age and breed given the genetic basis of many congenital diseases.

The following diagram summarizes the murmur characteristics of most congenital heart diseases, after which the diagnostic work-up of several are discussed. Treatment options will be presented in my next talk. 

PATENT DUCTUS ARTERIOSUS (PDA)

Patent ductus arteriosus is persistence of the communication between the main pulmonary artery and the descending aorta beyond the neonatal period, almost always resulting in left-to-right shunting from the aorta to the pulmonary artery and recirculation of the lungs and left side of the heart. Left uncorrected, the volume overload can cause left-sided congestive heart failure (lung edema) at potentially at a very young age depending on the size of the shunt. Patent ductus arteriosus is readily identified or at least suspected on physical examination by presence of the characteristic continuous left base heart murmur. In cats it is best heard more caudoventrally. Bounding femoral pulses are also quite characteristic. Thoracic radiography will often reveal left atrial and ventricular enlargement, evidence of pulmonary overcirculation (enlarged pulmonary arteries and veins), and distinct main pulmonary artery, ascending aorta, and "ductus bump" bulges on the DV view. Evidence of CHF may be present. The diagnosis can be almost certain on the basis of physical examination alone. Echocardiography serves to confirm the diagnosis, rule out other concurrent cardiac defects, and plan interventional closure (next talk).  […]