Small Animal Review

Mitral valve disease (MVD) due to mitral valve degeneration, a common disorder in dogs, results in left ventricular hypertrophy and left atrial dilatation, and often congestive heart failure. The diagnosis can be suspected from clinical examination and a diagnosis can be made using echocardiography, but neither can reliably assess the extent of myocardial damage or function. Measurements of blood atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP) concentrations are used to assess cardiac function, since plasma concentrations of these hormones increase with atrial or ventricular overload respectively, while myocardial damage can be assessed by assaying cardiac troponin.

The value of measuring ANP and troponin in dogs with naturally occurring MVD has been assessed by Hori et al (Evaluation of atrial natriuretic peptide and cardiac troponin I concentrations for assessment of disease severity in dogs with naturally occurring mitral valve disease. J Am Vet Med Assoc. 2020;256(3):340–348. https://doi.org/10.2460/javma.256.3.340). They carried out a prospective multicentre study involving 316 privately-owned dogs with mitral valve disease and 40 healthy control dogs. Within the diseased group, 142 were in stage B1, 102 in stage B2 and 72 in stage C, with 63 dogs receiving a variety of drugs. Stage B1 and B2 dogs were those not showing clinical signs, with stage B1 dogs having left atrium-to-aortic root ratio on echocardiography of <1.7 or a left ventricular internal diameter in diastole normalised to body weight of <1.7 cm/kg^0.294, while stage B2 dogs had values of ≥1.7 and ≥1.7 cm/kg^0.294 for the two measured parameters respectively. The stage C group contained those dogs with a history of clinical signs of congestive heart failure. As expected, the median vertebral heart score and left ventricular internal diameter at end diastole were greater in dogs with disease compared to the control group, and within the disease population this parameter along with median heart rate and fractional shortening were also higher in dogs with stage B2 and C than for those in stage B1.