Page 280 - Clinical Small Animal Internal Medicine

248 Section 3 Cardiovascular Disease

echocardiographic diagnosis of mitral valve prolapse is of 558 dogs affected by MMVD at different stages has
VetBooks.ir dependent on the morphology of the valve, and because shown that more than 70% dogs were alive at the end of
the follow‐up period of 6.6 years (Figure 25.2).
the normal mitral valve and mitral valve annulus present
In another study of 256 dogs affected with preclinical
a wide range of normality, we recommend that the
diagnosis of mitral valve prolapse should be confirmed MMVD, the overall mortality was 27%, with cardiac
in at least two echocardiographic views. Indeed, we have death accounting for 11% during the 833‐day observa-
recently reported that in dogs, mitral valve morphology tion period. The same study showed that 30/83 dogs that
is saddle shaped, similar to what has been reported in were available for reexamination progressed to a more
people. Therefore, using the right parasternal long‐axis advanced stage of MMVD. Reported risk factors associ-
view may lead to an overestimation of the mitral valve ated with progression of the disease or death included
prolapse. age, gender, intensity of heart murmur, degree of valve
The ACVIM consensus statement recommends prolapse, severity of valve lesions, the degree of mitral
thoracic radiography for all dogs with MMVD to assess valve regurgitation, degree of left atrial enlargement,
the hemodynamic significance of the murmur through severity of eccentric hypertrophy, rupture of chordae
evaluation of heart size and pulmonary vasculature and tendinae, and increased concentration of natriuretic
to obtain a baseline when the patient is asymptomatic. peptides. Left atrial enlargement, assessed by echocardi-
Careful evaluation of thoracic radiographs may help in ography, seems to represent one of the most reliable
diagnosing concomitant primary respiratory diseases independent predictors of death. The risk of death from
that may be the cause for clinical signs, such as cough or cardiac disease for dogs with a left atrium/aortic root
dyspnea. Thoracic radiographs, together with physical ratio exceeding 1.7 was 2.1 times that of dogs with
examination, are also essential for monitoring dogs with smaller atria.
MMVD. A change in radiographic cardiac dimensions Another study reported that plasma N‐terminal pro‐
observed between two different time points has been brain natriuretic peptide (NT‐proBNP) concentration
suggested as a powerful predictor of outcome in dogs and indexed left ventricular end‐diastolic diameter were
with MMVD. independent risk factors for development of first‐onset
CHF. The presence of pulmonary hypertension due to
MMVD was recently reported to be associated with
Prognosis
higher risk of death.
Myxomatous mitral valve disease is characterized by a
long preclinical period and many affectws dogs die for Therapy
reasons other than CHF. A study including a population
The Asymptomatic Dog (Stage B: ACVIM
1.0 Consensus)
ISACHC 1 Treatment of dogs with asymptomatic MMVD has been
ISACHC 2 a subject of controversy over the past years. This stage
0.8 ISACHC 3 includes dogs with the disease who have never developed
CHF. This group represents the majority of dogs diag-
0.6 nosed with MMVD. The ACVIM consensus suggests
that asymptomatic dogs could be further subdivided into
those with no radiographic or echocardiographic evi-
0.4
dence of cardiac enlargement (stage B1) and those with
evidence of cardiac remodeling suggested by the pres-
0.2 ence of left atrial and ventricular enlargement (stage B2).
This subclassification emphasizes the fact that asympto-
0.0 matic dogs are a heterogeneous group, including patients
with very mild disease as well as those with more
0 10 20 30 40 50 60 70 advanced disease that are more likely to develop clinical
Months
signs of CHF.
Figure 25.2 Survival curves for dogs with different stages of heart The ACVIM consensus group unanimously recom-
failure according to the International Small Animal Cardiac Health mended not treating dogs with MMVD in stage B1 of the
Council. Class 1 ISACHC are dogs with preclinical MMVD, class 2 disease. In contrast, no consensus was reached for dogs
ISACHC are dogs with moderate congestive heart failure, and class in stage B2. Two multicenter double‐blinded studies
3 ISACHC are dogs with severe heart failure (showing clinical signs
at rest and requiring close monitoring). Source: Borgarelli et al. evaluating the efficacy of enalapril on delaying the onset
(2008). Reproduced with permission of John Wiley. of CHF in stage 1B dogs with MMVD have shown no