Diagnosing and treating common congenital heart defects (Proceedings)
Congenital heart diseases are an important cause of morbidity and mortality in pediatric veterinary patients. The incidence of such defects is listed below.
Congenital Heart Diseases:
North American Study (canine) 0.46%-0.85%
Patent Ductus Arteriosus:
Is the most common congenital defect in dogs. It is a L- R shunting defect resulting from failure of closure of the left sixth aortic arch. If left untreated it results in left sided congestive heart failure. Clinically animals present with a Continuous (Machinery) Murmur at the left heart base with Hyperkinetic Femoral Pulses. A systolic murmur of mitral regurgitation may also be ausculted secondary to annular dilation from volume overload of the left ventricle.
Signalment: toy breeds (Corgi, Poodle, Maltese), German Shepard, Rottweiller are common large breeds affected. There tends to be a female:male (2:1) ratio.
Thoracic radiographs: Left ventricular enlargement, +/- L atrial enlargement, pulmonary overcirculation, "Ductus bump" (dilatation of the descending aortic), +/- pulmonary edema
Treatment – Multiple options to close the ductus now exist. Surgical closure has been the gold standard however interventional closure has overtaken surgery as the most common method in cardiology centers. Three devices have been studied and proven successful in our patients, Gianturco coil, Amplatz Plug, and the Canine ductal occluder.
Subaortic stenosis (SAS) is the second most common congenital defect in canine patients. It results in significant pathology and may cause sudden death. A fibrous, muscular or fibromuscular narrowing is formed just below the aortic valve in the LVOT that may involve the base of the aortic valve and the anterior leaflet of the mitral valve and anterior leaflet of the mitral valve since the annulus of these two structures is formed contiguously. The lesion may not be present at birth, can worsen over the first few months of life. MV dysplasia commonly associated.
Pathophysiology stenotic ring induces increase in LV afterload pressure overload→ concentric hypertrophy associated coronary arterial changes reduce coronary flow increased wall tension especially in subendocardial regions (↑ MVO2) → ischemia/arrhythmias.
Signalment : It is most commonly seen in large breed dogs such as Newfoundland, Golden Retriever, Rottweiller, Boxer, German Shepard; exact genetics unknown, suspect autosomal dominant with modifying genes or polygenic.
Exercise intolerance, syncope, sudden death, L-CHF (unusual) may all be present however a number of patients will present perfectly normal. Physical exam Cardiac auscultation often reveals an Ejection-type systolic murmur around left heart base (3rd - 4th ICS) of variable intensity radiates craniad and to the right, up the carotids and calvarium in some circumstances. The quality of the femoral pulses gives a strong physical exam clue as the severity of the stenosis. Reduced and late rising Pulses parvus et tardus suggest more severe disease.