Cardiovascular and circulatory disorders

Platelet disorders

• von Willebrand disease is an inherited, common disease found in both dogs and humans. It is characterized by a deficiency of a protein called von Willebrand factor, which is involved in blood clotting. The disease varies from mild to severe, depending on the amount of von Willebrand factor present in the dog. Signs include spontaneous bleeding and excessive bleeding following surgery, injury, or during an estrous cycle.
  
• Thrombocytopenia is a common condition in dogs characterized by low platelet counts. Platelets are used in clotting the blood, so dogs with this condition may have spontaneous bleeding or prolonged bleeding following surgery, injury, or during an estrous cycle. Causes include some rickettsial infections such as ehrlichiosis, cancers such as hemangiosarcoma, or immune-mediated disease.
  
• Thrombocytosis is a condition characterized by an excess of platelets. Most cases are physiologic (caused by exercise) or reactive (secondary to some cancers, blood loss, or certain drugs). Rarely the condition is caused by a primary bone marrow disorder. In this last case, the platelets may not function normally, causing the blood to not clot properly.
  
• Hemolytic anemia is a type of regenerative anemia found in dogs characterized by destruction of the red blood cell. The most important type is immune-mediated hemolytic anemia, which can be a primary disease or secondary to cancer, infection, drugs, or vaccinations. Antibodies are present on the cell surface, leading to lysis and severe anemia. Other causes of hemolytic lesion include hypophosphatemia, exposure to toxins such as lead, infections such as ehrlichiosis or babesiosis, and rarely, neonatal isoerythrolysis. The behavioral condition pica, especially when involving the eating of concrete dust, tile grout, or sand, may be a sign of hemolytic anemia, indicating the need for a complete blood count to investigate a possible diagnosis.

Heart diseases

• Degenerative mitral valve disease is a common cause of congestive heart failure in dogs, especially small, older dogs. The leaflets of the valve become thickened and nodular, leading to mitral valve regurgitation and volume overload of the left side of the heart. Cavalier King Charles Spaniels have an inherited form of this disease.
  
• Dilated cardiomyopathy is a disease of heart muscle resulting in atrial and ventricular dilation. It is seen in large dog breeds such as Boxers, Great Danes, and Dobermanns. It is usually idiopathic, but can also be caused by taurine deficiency in Cocker Spaniels or doxorubicin use. Dilated cardiomyopathy usually results in congestive heart failure.
  
• Congestive heart failure is any heart disease that results in the inability to put out enough blood to meet the dog's needs. It can be caused by the above two diseases, heat stroke, electric shock, injury, infection, developmental heart defects, or high blood pressure. Signs depend on which side of the heart is affected. Left-sided heart failure may result in coughing and difficulty breathing from a build-up of fluid in the lungs (pulmonary edema) and fainting. Right-sided heart failure may result in a build-up of fluid in the abdomen (ascites), fluid around the lungs (pleural effusion), or peripheral edema.
  
• Sick sinus syndrome is most commonly seen in female Miniature Schnauzers. It is characterized by sinoatrial node dysfunction and often includes atrioventricular node disease and bundle branch block. Electrocardiogram findings include sinus bradycardia, sinus arrest, sinoatrial heart block, and asystole. The major sign is fainting.
  
• Aortic stenosis is a congenital disease in dogs characterized by left ventricular outflow tract obstruction. It is inherited in Newfoundlands, and also found in Golden Retrievers, Rottweilers, Boxers, Bulldogs, German Shepherd Dogs, and Samoyeds. Signs include fainting and exercise intolerance.
  
• Pulmonic stenosis is a congenital disease in dogs characterized by right ventricular outflow tract obstruction. Most commonly the narrowing occurs at the pulmonary valve. The most commonly affected breeds include terriers, Bulldogs, Miniature Schnauzers, Chihuahuas, Samoyeds, Beagles, Keeshonds, Mastiffs, and Bullmastiffs. Signs include exercise intolerance, but often there is only a heart murmur.
  
• Ventricular septal defect is a hole in the division between the heart ventricles. It is a congenital disease in dogs. There usually are no signs in dogs except for a heart murmur.
  
• Atrial septal defect is a hole in the division between the heart atria. It is an uncommon condition in dogs. Most are not clinically significant, but large defects may cause heart failure, cyanosis, and exercise intolerance.
  
• Tetralogy of Fallot is a congenital heart defect in dogs that includes four separate defects: pulmonic stenosis, a ventricular septal defect, right ventricular hypertrophy, and an overriding aorta. Keeshonds and Bulldogs are predisposed. Signs include cyanosis and exercise intolerance.
  
• Patent ductus arteriosus is the most common congenital heart defect in dogs in the United States. It is inherited in toy and miniature Poodles, and seen commonly in Pomeranians, Bichon Frises, and Malteses. Signs include cough and exercise intolerance.
  
• Heart valve dysplasia (including mitral and tricuspid valve dysplasia) is a congenital heart defect in dogs. Dysplasia of the mitral and tricuspid valves - also known as the atrioventricular (AV) valves - can appear as thickened, shortened, or notched valves.
  
• Cor triatriatum, specifically cor triatriatum dexter, occurs in dogs and is characterized by a fibrous division of the right atrium. It can be treated by balloon valvuloplasty.
  
• Pericardial effusion is a collection of fluid in the pericardium. It is usually serous (clear or yellow fluid) or serosanguinous (bloody fluid). Serous accumulation is caused by heart failure, peritoneopericardial diaphragmatic hernias, uremia, pericardial cysts, or hypoalbuminemia. Serosanguinous accumulation can be caused by cancer, usually hemangiosarcoma, idiopathic disease, trauma, clotting disorders, or left atrial rupture. Rarely pericardial effusion can be caused by infection and consist of pus. Drainage of the fluid is the ideal treatment.
  
• Pulmonary hypertension is high pressure in the pulmonary artery. In dogs it can be caused by heartworm disease or pulmonary thromboembolism. It can result in right-sided heart disease (cor pulmonale). Signs include difficulty breathing, cyanosis, and exercise intolerance.