Congenital heart conditions occur as the result of abnormal heart formation during gestational development. Heart conditions can occur in the valves, heart chambers, vessels or the connections between any of these. In dogs, the main malformations include patent ductus arteriosus, pulmonic stenosis, subaortic stenosis and Tetralogy of Fallot. The prognosis for dogs born with congenital heart issues depends on the severity of the malformation, early detection of the condition and possible treatment options. If left untreated, many congenital heart issues can lead to death within the first year of life.
An Open Valve
In the womb the ductus arteriosus connects a puppy’s aorta to the pulmonary artery, allowing blood to flow around the undeveloped lungs for oxygen. In normal development, this vessel closes after birth, shifting blood flow into the lungs in order to collect oxygen. In patent ductus arteriosus, the ductus arteriosus remains open, diverting blood flow and increasing blood volume in the veins, arteries and left side of the heart, often causing left-sided congestive heart failure. Symptoms include coughing, exercise intolerance, rapid breathing, irregular heart beat and stunted growth. Surgical correction is necessary to close the vessel. Dogs left untreated typically die within the first year of life. Predisposed breeds include the poodle, Pomeranian, collie, Shetland sheepdog, German shepherd, cocker spaniel and English springer spaniel.
When the Opening Narrows
In pulmonic stenosis, the pulmonic valve that connects the pulmonary artery to the right ventricle has a narrow opening, resulting in blood flow obstruction. This narrowing can occur in the valve, slightly below the valve or just inside the artery. Mild stenosis often presents no symptoms or a simple heart murmur. However, severe stenosis can result in right-sided congestive heart failure within the first year if left untreated. Surgical intervention is necessary in severe cases. Breeds predisposed to pulmonic stenosis include the beagle, boxer, Chihuahua, cocker spaniel, English bulldog, mastiff, miniature schnauzer, Samoyed, Scottish terrier and wirehaired fox terrier.
Another Narrowing Condition
Similar to pulmonic stenosis, subaortic stenosis is a narrowing just below the aortic valve that results in restricted blood flow and increased work by the left ventricle of the heart. Mild cases can be asymptomatic, while severe cases can lead to left-sided congestive heart failure. Symptoms include heart murmur, coughing, fainting, blue-tinged gums, fatigue, exercise intolerance and sudden death. Treatments include surgical intervention or medication, such as beta blockers. Predisposed breeds include the boxer, German shepherd, German short-haired pointer, golden retriever, great Dane, Newfoundland and Rottweiler.
Malformation of the Heart
Tetralogy of Fallot is a congenital heart condition where four abnormalities occur. In this condition, a dog suffers from a hole between the two ventricles, heart muscle thickening, incorrect aorta placement and pulmonic stenosis. These abnormalities cause a large amount of blood to redirect around the lungs, resulting in low blood oxygen. Symptoms include shortness of breath, heart murmurs, increased breathing rate, dark or blue-tinged gums, loss of consciousness or seizures. Exercise restrictions, removal of blood volume, medication and surgical intervention are treatment options. Beagles, English bulldogs, miniature poodles, miniature schnauzers, fox terriers and Keeshonds are breeds predisposed to this abnormality.
- Michigan Veterinary Specialists: Congenital Heart Disease in Dogs
- PetMD: Heart Defect (Congenital) in Dogs
- WebMD: Congenital Heart Disease in Dogs
- PetMD: Congenital Heart Defect (Pulmonic Stenosis) in Dogs
- Mar Vista Animal Medical Center: Subaortic Stenosis
- Veterinary Diagnostics and Cardiac Evaluations: Subaortic Stenosis (SAS)
- PetMD: Tetralogy of Fallot in Dogs
- The University of Sydney Faculty of Veterinary Science: Disorder -- Tetralogy of Fallot
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