Heart murmurs in puppies and adult dogs

Abstract

Heart murmurs in puppies and adult dogs are common findings in first-opinion veterinary practices during routine health checks. Heart murmurs in puppies can be innocent or pathological. Differentiating between innocent and pathological heart murmurs in puppies is important as, for some congenital cardiac diseases, life-saving treatment is available if early intervention is initiated. Therefore, referral of puppies with a heart murmur to a cardiology specialist is recommended to reveal congenital heart diseases. Ideally, referral takes place before the puppy is sold to a new owner and before the puppy develops clinical signs of heart disease. Heart murmurs in adult dogs are, in most cases, the result of an underlying heart disease. The most frequently diagnosed underlying condition is myxomatous mitral valve degeneration. There are international guidelines (included in the ACVIM Consensus Statement) for the management of this common disease. The guidelines describe a staging system and give recommendations for both diagnostics and treatment. The first part of this thesis describes that innocent heart murmurs in puppies typically disappear by three months of age, but they can persist up to 9 months. This result emphasizes that postponing the referral of a puppy with a murmur to a cardiology specialist until a murmur disappears is a dangerous strategy because puppies can die of congenital heart disease as early as three months of age. However, in first-opinion veterinary practices this is a commonly heard recommendation to try to distinguish innocent from pathologic murmur, when veterinarians are uncertain about the results of heart auscultation. The main part of the thesis focusses on how veterinarians assess, document, and interpret heart murmurs. The results suggest that first-opinion veterinarians detect murmurs easily, but they have difficulties in recognizing and documenting innocent murmurs in puppies. This can lead to an erroneous interpretation of a pathologic murmur as being innocent. In adult dogs, 60% of the surveyed veterinarians followed the staging system of the international guidelines on myxomatous mitral valve degeneration. The survey results show that veterinarians can diagnose cardiogenic pulmonary edema, but they have difficulties differentiating stage B1 from stage B2 in the subclinical stage of the disease. Unfortunately, 13% did not recommend additional examination in a dog with a moderate-intensity heart murmur, despite the recommendations in the international guidelines. However, most veterinarians correctly applied the newest study results to treating a dog with myxomatous mitral valve degeneration. The therapeutic approach varied more with increasing severity of the valve disease. This finding reflects the disagreement on medical management among the experts who wrote the consensus guidelines. A surprising finding was that none of the veterinarians recommended surgery for the valve disease. This thesis shows that integrating high-quality veterinary care into everyday practice remains challenging in veterinary medicine.