One in 10 dogs that present to primary care veterinary clinics may have heart disease. And about 75% of dogs with heart disease have chronic valvular heart disease (CVHD). CVHD most often affects the mitral valve, but in about 30% of cases it also affects the tricuspid valve. While veterinarians have long used classification systems (e.g. the modified New York Heart Association system: Class I, II, III, and IV) to judge severity and clinical signs in patients with heart failure, such systems are based on relatively subjective assessments of clinical signs.
To more objectively categorize patients and to complement the current classification system, the American College of Veterinary Internal Medicine (ACVIM) Specialty of Cardiology consensus panel has developed a set of guidelines for the diagnosis and treatment of CVHD. This new classification system is designed to help veterinary clinicians identify and treat CVHD by using a method similar to that already used for cancer patients. These guidelines integrate disease stage and clinical status with medication and dietary recommendations.
The guidelines are divided into four basic stages (A-D) of heart disease and heart failure, and for each stage, a consensus recommendation on diagnostic approach and treatment is given. In some instances, evidence for the efficacy of a diagnostic or treatment option was absent, conflicting, or weak. Thus the panel did not reach a consensus based on available evidence and collective clinical experience, and the panel's opinions are described separately in the guidelines.
These dogs are at high risk for heart failure, but have no heart murmur. They include small breeds, especially those with a predisposition to develop valvular disease (e.g. Cavalier King Charles spaniels). No drug or dietary therapies are recommended. If mitral regurgitation is identified during the normal breeding age of less than 6 to 8 years, potential breeding stock should no longer be bred.
These patients have a structural cardiac abnormality but have never had clinical signs of heart failure. They are usually identified during auscultation and have a heart murmur consistent with mitral valve insufficiency. Stage B is divided into B1 and B2 groups based on blood work, urinalysis, blood pressure measurement, radiography, and echocardiography.
Stage B1 patients are normotensive and have no abnormalities identified by the above tests or have equivocal enlargement of the left atrium or left ventricle or both. No drug or dietary therapies are recommended, and these dogs should be reevaluated with radiography or echocardiography with Doppler studies in about one year or perhaps sooner in large breeds.
Stage B2 patients are also normotensive but have an enlarged left atrium, left ventricle, or both. A consensus for drug and dietary therapies could not be reached for this group, but the panel provides opinions on treatment strategies that could be considered.
Stages C and D
Stage C dogs have a structural cardiac abnormality and current or previous clinical signs of heart failure caused by CVHD. Guidelines for standard drug therapy are provided for acute (in-hospital) and chronic (at home) treatment and management of Stage C patients as well as dogs classified as Stage D (CVHD that is refractory to Stage C treatments).
The treatments discussed include furosemide, oxygen supplementation, mechanical fluid removal (abdominocentesis and thoracocentesis), pimobendan, sodium nitoprusside, and enalapril, as well as treating anxiety and providing optimal nursing care and a home-based extended care program. Dietary therapy includes feeding to avoid loss of muscle mass, to ensure adequate protein intake, and to modestly restrict sodium intake. Acute and chronic drug therapy recommendations for Stage D dogs are more aggressive, since these dogs have been unsuccessfully treated already. Dietary recommendations for Stage C and D patients are similar.
For the first time, clinicians have a classification system for dogs with CVHD that ties disease stage with specific diagnosis and treatment recommendations. These guidelines give veterinarians a new tool to better tackle these tough cases with confidence and consistency.
Atkins C, Bonagura J, Ettinger S, et al. ACVIM Consensus Statement: Guidelines for the diagnosis and treatment of canine chronic valvular heart disease. J Vet Intern Med 2009;23:1142-1150.