Not so fast!

Over at the gold mine for Cavalier health research Cavalierhealth.org they bring us conflicting veterinary views on when pimodendan aka vetmedin should be given to a dog with Mitrial Valve Degeneration (MVD). First we have Cardiologist Philip Fox claiming EPIC Study makes echocardiography optional in prescribing pimobendan before heart failure.

"In a Fall 2016 newsletter column, USA veterinary cardiologist Dr. Philip Fox (right) asserts that in determining when to start administering pimobendan to MVD-affected dogs under the EPIC Study, either x-rays orechocardiography may be used. Specifically, he writes:
"In light of these findings, clinicians should change how they diagnose and manage MVD. Dogs with heart murmurs should be screened early, rather than wait for clinical signs of coughing or respiratory distress to develop. Assessment can be effectively made using history and physical examination along with the added benefit of chest radiography and/or echocardiography." (Emphasis added.)"

The editor of Cavalierhealth.org notes that their greatest fear has happened after the EPIC Study report

"There you have it. Our greatest fear about the terribly flawed EPIC Study report is that it would encourage veterinarians to skip echos entirely and diagnose heart enlargement solely based upon x-rays.  (See our March 2017 blog article, "Will general practice vets cut corners to prematurely prescribe pimobendan to MVD-affected cavaliers?", for more details.)"

But then Cardiologist Mark Rishniw says "Not so fast!" in prescribing pimobendan to all heart-enlarged MVD dogs. The editor of Cavalierhealth.org ​tells us that Cardiologist Mark Rishniw "questions the basis for the EPIC Study authors' optimism about starting all heart-enlarged MVD-affected dogs on pimobendan, regardless of the extent and/or rapidity of the enlargement. From the EPIC Study authors' viewpoint, he writes"

"Essentially, the risk of developing Chronic Heart Failure (CHF) or dying was almost halved, regardless of how bad the dog’s disease was going into the study. On the face of it, this sounds great. Based on this information alone, every dog with MMVD and left atrial enlargement (correctly identified!) would benefit from pimobendan treatment. Not so fast! The decision to treat a dog requires additional information to be considered. First, the baseline risk of developing CHF needs to be determined, i.e., what is the chance that this dog will actually develop CHF at some point in the future?" (Emphasis added.)

"He then takes into account the statistics from the study and asks this ultimate question:"

"Is 'earlier' treatment better than 'later' treatment? The survival curves provide clues to this answer. ... Now, if there was a clear benefit of 'earlier' rather than 'later,' we might expect the survival curves to diverge, ie., continue to move further and further apart. But they don’t. For the majority of the study, they remain parallel. So, the benefit with more severely affected dogs is about 300 days, and the benefit with the least severely affected dogs is about 300 days. This suggests that taking the more measured approach of waiting until a dog exhibits evidence of disease progression before instituting therapy is not compromising that dog nor reducing the benefit of the drug. And, dogs that were never going to progress to more severe disease and never develop CHF would not be subjected to needless drug administration (and needless expenses)." (Emphasis added.)

A significant number of Cavaliers that are diagnosed with a murmur do not progress to CHF and with suggesting as Cardiologist Phillip Fox does, that just an x-ray can be used for determining when to prescribe pimobendan with heart enlargement in all dogs, regardless of breed, using a VHS value of 10.5+, is a measurement so low that most Cavaliers that don't have MVD could be considered a candidate for being prescribed pimobendan. I think the more measured approach of Cardiologist Mark Rishniw of the dog exhibiting evidence of disease progression, which "is not compromising that dog nor reducing the benefit of the drugs" is certainly a better option than dogs being "subjected to needless drug administration (and needless expense)."