Degenerative Valve Disease: Treatment and Testing
Simon Swift
 
Degenerative valvular disease remains one of the commonest causes of morbidity and mortality in the cavalier King Charles spaniel. There has been progress in the treatment of degenerative valve disease with several studies reporting either new medications or novel uses of existing drugs. The aims however, remain the same, namely to slow the progress of the disease and improve the quality of life for those dogs affected. Ultimately, as the disease has been shown to be inherited(1), the solution remains with attempts to use testing to eliminate the disease from the breed. Current this involves auscultation and the breeding guidelines. These state that the brood bitch should be a minimum of 2½ years old with a clear heart, and parents with clear heart certificates, issued at 5 years or older. In addition, the stud dog should preferably be at least 2½ years old with a clear heart and with parents with clear heart certificates issued at 5 years of age or older.

Treatment

Sadly, despite several trials(2 and 3) there is no evidence that treatment with an angiotensin converting enzyme (ACE) inhibitor before the onset of heart failure delays the onset of heart failure. No trials have been performed using Pimobendan in this group of dogs and there is little theoretical basis for its use. Interestingly, asymptomatic dogs fed a “heart diet” had a reduction in heart size(4). The “heart diet” included decrease sodium, increased levels of arginine, carnitine and taurine as well as supplementation with omega 3 fatty acids. Whether this translates into a delay before heart failure develops remains to be proven.

Heart failure is characterised by breathing difficulties, poor appetite, weight loss, exercise intolerance and a cough usually at night. Once heart failure develops, diuretics such as frusemide are required to control the oedema in the lungs. The QUEST study confirmed that pimobendan prolongs survival significantly longer than an ACE inhibitor when combined with frusemide(2). However, although there is no data concerning the combination with an ACE inhibitor, most cardiologists would add an ACE inhibitor to frusemide and pimobendan. A recent study indicated that the addition of a mild diuretic, spironolactone, improves quality of life and prolongs life(5). This drug counteracts the effects of a natural hormone, aldosterone, which is increased in heart failure and has harmful consequences.

Unfortunately, the disease is progressive and many dogs progress to advanced heart failure. Other drugs may be indicated to:
  • Reduce systemic blood pressure and increase output
  • Control arrhythmias
  • Reduce pulmonary hypertension
  • Increased doses or frequency of diuretics
Testing

The initial scheme was established over 20 years ago. Due to the shortage of veterinary surgeons with further qualifications in cardiology and to encourage participation, it was decided at that time to allow all vets to complete the forms. The forms are returned and entered on the club database which now contains over 9100 dogs. However, only the results from veterinary surgeons with further qualifications in cardiology were used in the analysis of the database. Since then, heart testing schemes have been set up for other breeds such as boxers and Newfoundlands. These schemes use veterinary surgeons with further qualifications in cardiology such as certificates or diplomas. In an attempt to maintain uniformity, a panel of veterinary cardiologists was established and maintained by the Veterinary Cardiovascular Society (VCS). This list is available on the website (http://www.bsava.org.uk/vcs/). The British Veterinary Association, VCS and Kennel Club have agreed to take the current heart testing schemes run by the breed clubs with the help of interested members of the VCS into the official Breed Schemes as part of the accredited breeders program. So they will be run along similar guidelines to the current hip, elbow and eye schemes. Permanent identification will be required. Only forms completed by vets on the auscultation panel will be entered into the database and used for the “over 5” years clear list.

The talk will show the results from the database up to 2009. Cardiologists have tested more dogs than GP vets and this ratio is increasing. A recent study(6) in Sweden indicated a lack of improvement in the prevalence of degenerative mitral valve disease despite their breeding program. However, their breeding program is not identical to the UK scheme and these schemes are long term projects. As a result, the time frame used in the study may have been too short to show improvement and the results not applicable to the UK.

References
  1. Heritability of Premature Mitral Valve Disease in Cavalier King Charles Spaniels.
    T. Lewis, S Swift et al The Veterinary Journal 2010 Epub
  2. Effects of Pimobendan or Benazepril Hydrochloride on Survival Times in Dogs with Congestive Heart Failure Caused by Naturally Occurring Myxomatous Mitral Valve Disease: The QUEST Study.
    J Haggstrom, A Boswood, M O’Grady, O Jons, S Smith, S Swift et al J Vet Int Med 2008 1 – 12
  3. Results of the Veterinary Enalapril Trial to prove Reduction in onset of Heart Failure in Dogs Chronically Treated with Enalapril Alone for Compensated, Natrually Occurring Mitral Valve Insufficiency.
    C. Atkins, B. Keene, W. Brown et al J Am Vet Med Ass 2007 231 1061–1069
  4. Effects of Dietary Modification in Dogs with Early Chronic Valvular Disease.
    L. Freeman, J. Rush, and P Markwell J Vet Intern Med 2006 200 1116–1126
  5. Efficacy of Spironolactone on Survival in Dogs with Naturally Occurring Mitral Regurgitation Caused by Myxomatous Mitral Valve Disease.
    F. Bernay, J. Bland. J. Hagstrom et al J Vet Intern Med 2010 24 331–341
  6. Evaluation of the Swedish Breeding Program for Cavalier King Charles Spaniels.
    T. Lundin and C. Kvart 2010 Acta Vet Scand 52 54
 
 
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