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Summary of results of PROTECT clinical trial

Pimobendan (brand name Vetmedin) is used in dogs with dilated cardiomyopathy (DCM) to treat the symptoms of congestive heart failure (CHF). The PROTECT trial was set up to investigate whether the drug, if administered long-term to dobermanns with preclinical evidence of DCM, detected on the basis of echocardiography, could delay the onset of CHF and/or sudden death and in doing so prolong survival. As most dobermann breeders know, dobes of 4-9 years of age were offered free echocardiogram tests to identify dogs with evidence of preclinical DCM. Seventy-six dogs from ten centres in the UK and North America were enrolled into the trial, where half were given pimobendan and half a placebo. The median time for continuing this treatment was 427 days. 

The conclusions were as follows:

1. Dogs on pimobendan took significantly longer to reach the primary endpoint (defined as onset of CHF or sudden cardiac death) compared to those on placebo (median from start of trial to onset of CHF or sudden death 718 days vs 441). Thus, the dogs on pimobendan had a median additional time of about 9 months free of CHF or sudden death.

2. Dogs on pimobendan survived significantly longer (median from enrolment on trial to death 623 days vs 466; about 6 months longer). It may seem curious that the median time to death is shorter than time to onset above, but this is due to some dogs dying of other causes early in the trial.

3. Reduced systolic function, increased heart rate and =4 ventricular premature complexes (VPCs) on a 3 minute ECG are indicative of increased risk of developing CHF or experiencing sudden death. 

4. The drug decreased heart size in the majority of dogs that received it.

5. Although there were some gastrointestinal side-effects in a minority of dogs, none were serious enough to warrant withdrawing them from the trial.

These are very encouraging results that clearly indicate that dobermanns with preclinical evidence of DCM associated with ventricular dilatation should be given pimobendan on a long-term basis to improve their survival time and delay the onset of heart failure. Note that some dogs may have arrhythmias, but not increased heart size; these were not included in the study, so it is not known whether the therapy would help in this group.

I would like to note my thanks to the corresponding author of the article, Dr Adrian Boswood, who kindly reviewed and commented on the draft of this lay summary.

Summerfield NJ, Boswood A et al, Efficacy of pimobendan in the prevention of congestive heart failure or sudden death in doberman pinschers with preclinical dilated cardiomyopathy (the PROTECT Study) 2012, Journal of Veterinary Internal Medicine, vol 26, pages 1337-1349

© 2012 Sue Thorn

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