Early disease detection for mitral valve disease

Cardiac disease is “the third most common cause of death in dogs, behind cancer and old age,” stated Brian Scansen, DVM, MS, DACVIM (Cardiology) of the Cardiac Education Group, noting that approximately 10% of dogs presenting to a veterinarian have heart disease. Heart disease in dogs often exists before clinical signs of disease are evident with the earliest indicators of its presence found in the patient’s history and physical examination.

During the 2026 Veterinary Meeting & Expo in Orlando, Florida, Scansen was joined by Sonya Gordon, DVM, DVSc, DACVIM (Cardiology) to discuss screening for mitral valve disease in canine patients.¹ Gordon stressed the importance of early disease detection, noting that “we can change what is going to happen for this dog if we identify disease early.”

The stages of mitral valve disease

Scansen noted that “A staging system is useful to strategy patients to characterize where they are in their disease process, and to normalize diagnostic and therapeutic strategies for each stage of disease.” The staging scheme for myxomatous mitral valve disease was last updated by the American College of Veterinary Internal Medicine in 2019 and includes:²

• Stage A: Dogs at risk for development of heart disease based on breed and/or age. These dogs do not have any structural changes to their heart, and both auscultation and imaging are normal.
• Stage B: Dogs with structural heart disease but no clinical signs. These patients will have a murmur on auscultation, as the presence of a murmur usually precedes any clinical signs of disease. This stage is further divided into:
  • Stage B1: Heart disease is present but no cardiac remodeling has occurred. Radiographs will have a normal cardiac silhouette.
  • Stage B2: Cardiac remodeling is now present, though patients remain asymptomatic. Radiographs will show changes in the cardiac silhouette. This stage is the threshold for treatment with pimobendan, which extends disease free interval and overall survival, which Scansen and Godon refer to as “health span.”

• Stage C: Dogs have current or previous clinical signs of congestive heart failure. These patients may require emergency treatment at initial presentation, followed by ongoing maintenance therapy.
• Stage D: Dogs with refractory, end-stage congestive heart failure.

Understanding the stages of disease allows veterinarians to target their screening efforts to maximize the chance of early disease detection and provide early intervention.

Client education in the pre-clinical stage

For patients in Stage A, the veterinarian’s primary role is client education. Veterinarians should inform clients of their pets’ increased risk for mitral valve disease based on breed, weight, and/or age considerations. The importance of regular wellness examinations should be stressed, as detection of a heart murmur on auscultation is often the first sign of disease. “The best test to screen for this disease is part of a normal physical examination,” explained Gordon.

Scansen noted that for patients presenting with early heart disease, there are “often no notable signs identified by the client, but when [the veterinarians] starts to probe more specifically, subtle signs will become more apparent.” Thus, it is important to take a thorough history at each appointment but also advise owners what signs they should monitor for, including changes in exercise tolerance, increased hiding behavior, increased weakness or syncope, cough, changes in respiration, abdominal distention, and weight loss. Nutritional discussions are also important for these patients.

Ultimately, preparing clients for the potential of heart disease early in their dog’s life or disease process helps clients to feel more empowered and prepared in the event their pet develops heart disease.

The cardiovascular examination

“The purpose of a thorough cardiovascular examination is to determine if heart disease is present,” said Scansen. Abnormal findings on an examination can also help to evaluate severity, narrow the differential diagnosis list, direct diagnostics, and dictate the urgency of treatment.

Careful auscultation is the most important step of the exam and should be performed in a quiet room with good patient restraint. Scansen recommends trying “to optimize the environment as much as possible” so that subtle sounds aren’t missed. Auscultation should be performed over all cardiac valves and lung fields. The patient should ideally be standing, with sternal recumbency the second-best position. Thorough auscultation is more difficult to perform on a patient in lateral recumbency.

Abnormalities on auscultation may include the presence of a murmur, changes in heart rhythm, or other abnormal heart sounds. Gordon shares that any abnormal heart sound should be a sign to pay close attention. For murmurs, noting where the point of maximal intensity is can help to narrow the differential diagnosis list. Gordon reminds veterinarians that the murmur grade does not necessarily correlate with disease severity.

In addition to auscultation, the cardiovascular examination should include assessments of overall health, including body condition score and muscle condition score, mentation, posture, mucus membrane color, capillary refill time, respiratory effort, arterial pulse quality and symmetry, palpation of the chest to check for a thrill and location of the apex beat, and checking for the presence of jugular venous distention or pulsation. Gordon recommends trending a patient’s respiratory rate over time, which means clearly noting a rate (not just “panting”) in the medical record on each examination.

What comes next

Detection of a heart murmur and/or other abnormalities on physical examination should prompt a discussion with the client about potential causes of the abnormalities and recommended diagnostics. For patients with a murmur, next step diagnostics include imaging to evaluate heart size, including radiographs and echocardiogram. For an arrhythmia, an ECG should be discussed. Gordon notes that these discussions should include considerations of any budgetary factors the client is experiencing. The results of these tests will determine if any treatment is indicated.

References

1. Scansen B and Gordon S. Before the murmur: Screening for Mitral Valve Disease. Presented at VMX 2026: Orlando, Florida. January __, 2026.
2. Keene BW, Atkins CE, Bonagura JD, et al. ACVIM consensus guidelines for the diagnosis and treatment of myxomatous mitral valve disease in dogs. J Vet Intern Med. 2019; 33: 1127–1140. https://doi.org/10.1111/jvim.15488