What GPs should know about the B2 dog and preclinical heart disease
Bottom line
A new Clinician’s Brief partner podcast, “The B2 Dog: What Every General Practitioner Should Know About Preclinical Heart Disease With Dr. Visser,” puts fresh attention on a familiar but often challenging case for small animal practice: the asymptomatic dog with stage B2 myxomatous mitral valve disease (MMVD). In the episode, veterinary cardiologist Dr. Lance Visser reviews how to recognize preclinical heart disease, why the B2 distinction matters, and how the regulatory landscape has shifted since the FDA expanded Vetmedin’s label to include delaying the onset of congestive heart failure in dogs with stage B2 preclinical MMVD. That expanded indication followed earlier conditional approval and was backed by the landmark EPIC trial, which showed pimobendan significantly prolonged the time to heart failure or cardiac-related death in dogs with cardiomegaly caused by preclinical MMVD. (cebroker.com)
Why it matters: For general practitioners, the practical issue isn’t just hearing a murmur, it’s identifying which dogs have crossed from B1 into B2, where treatment changes. ACVIM’s consensus guidelines define stage B2 as asymptomatic MMVD with evidence of cardiac remodeling, and they recommend pimobendan for dogs that meet those criteria. That makes accurate staging, client communication, and timely referral or imaging central to case management, especially because B1 dogs are monitored, while B2 dogs may benefit from starting therapy before clinical signs appear. (pmc.ncbi.nlm.nih.gov)
What to watch: Expect continued focus on earlier detection workflows in general practice, including when to image, when to refer, and how the newer labeled indications for chewable and oral solution pimobendan shape everyday management. (fda.gov)
Key facts
- Topic
- Preclinical heart disease in dogs with stage B2 myxomatous mitral valve disease (MMVD)
- Expert featured
- Veterinary cardiologist Dr. Lance Visser
- Stage B2 definition
- Asymptomatic MMVD with evidence of cardiac remodeling
- Guideline
- 2019 ACVIM consensus guidelines recommend pimobendan for stage B2 MMVD
- Key study
- EPIC trial
- EPIC finding
- Pimobendan significantly prolonged time to heart failure or cardiac-related death in dogs with cardiomegaly caused by preclinical MMVD
- FDA action
- FDA expanded Vetmedin’s label to delay onset of congestive heart failure in dogs with stage B2 preclinical MMVD
- Regulatory history
- Vetmedin-CA1 was conditionally approved in 2022
- Company
- Boehringer Ingelheim
A Clinician’s Brief partner podcast featuring veterinary cardiologist Dr. Lance Visser is spotlighting one of the most common cardiology decision points in primary care: what to do with the dog that appears clinically normal but meets stage B2 criteria for preclinical heart disease. The episode centers on myxomatous mitral valve disease, or MMVD, and comes at a time when the treatment conversation has become more concrete for general practitioners because the FDA has now fully approved pimobendan labeling for delaying the onset of congestive heart failure in dogs with stage B2 preclinical MMVD. (cebroker.com)
That matters because stage B2 has been a pivotal category in canine cardiology for years. Under ACVIM guidance, stage B refers to dogs with structural heart disease but no clinical signs of heart failure, with B1 reserved for dogs without cardiac remodeling and B2 for dogs with remodeling significant enough to change management. The 2019 ACVIM consensus guidelines formalized the recommendation to use pimobendan in dogs with stage B2 MMVD, reflecting the profession’s shift toward intervening before overt congestive heart failure develops. (pmc.ncbi.nlm.nih.gov)
The evidence base behind that recommendation is the EPIC study, a randomized clinical trial published in the Journal of Veterinary Internal Medicine in 2016. Investigators found that dogs with preclinical MMVD and cardiomegaly treated with pimobendan had a significantly longer time to the composite endpoint of congestive heart failure, cardiac death, or euthanasia for cardiac reasons than dogs receiving placebo. The study established preclinical B2 disease as a treatable stage rather than simply a monitoring category, and it remains a core reference point in continuing education and product labeling. (pmc.ncbi.nlm.nih.gov)
The regulatory story has evolved, too. FDA first conditionally approved Vetmedin-CA1 for this indication in 2022, calling it the first drug intended to delay onset of congestive heart failure in dogs with stage B2 preclinical MMVD. In December 2025, the agency announced full approval of Vetmedin chewable tablets for that use after Boehringer Ingelheim submitted the required effectiveness data, and FDA listings show the oral solution later gained the same B2 indication as well. Boehringer has framed the approval as a milestone not only for canine cardiology, but also for the agency’s expanded conditional approval pathway. (fda.gov)
Industry and professional commentary have largely treated the development as validation of what many cardiologists and informed GPs were already doing based on the literature. Clinician education materials tied to the podcast explicitly position the episode around staging, diagnostic criteria, EPIC data, and what the newer FDA approval means in practice. AAHA’s coverage similarly emphasized that the expanded label officially aligns approved use with stage B2 management. (cebroker.com)
Why it matters: For veterinary professionals, the biggest takeaway is that success in B2 cases depends less on drug familiarity than on case identification. A murmur alone doesn’t make a dog B2. Practices need a reliable pathway for distinguishing B1 from B2, whether through thoracic radiography, echocardiography, biomarker use in selected cases, or cardiology referral. That distinction affects treatment, monitoring intervals, and how teams counsel pet parents about prognosis. It also creates an opportunity for general practice teams to catch progression earlier, before the dog presents in respiratory distress or with advanced remodeling. (pmc.ncbi.nlm.nih.gov)
There’s also a workflow implication. As more practices incorporate murmur follow-up protocols and as approved formulations broaden, B2 management may become more standardized in first-opinion settings. That could mean more intentional screening of older small-breed dogs, clearer thresholds for referral, and more structured follow-up once a dog starts pimobendan. For clinics, this is as much a systems issue as a cardiology issue. (animalhealth.boehringer-ingelheim.com)
What to watch: The next phase will likely center on implementation: how consistently GPs apply B2 criteria, whether access to imaging remains a bottleneck, and how continuing education like this podcast shapes earlier, more confident intervention in dogs with preclinical MMVD. (cebroker.com)