Page 154 - Small Animal Internal Medicine, 6th Edition

126 PART I Cardiovascular System Disorders

PRECLINICAL (STAGE B) CVMD

VetBooks.ir It is important to assess the severity of MR and cardiac
remodelling. This helps determine risk for CHF and guide
recommendations for monitoring, management, and reeval-
uation. Thoracic radiographs and NT-proBNP are useful for
this. However, especially as the disease advances, echocar-
diography becomes more important to assess LA and LV
size, ventricular function, and other factors.

STAGE B1
Thoracic radiographs, blood pressure (BP) measurement,
and plasma NT-proBNP or echocardiography generally are
recommended yearly to monitor dogs with stage B1 disease;
FIG 6.4 although semiannual rechecks for large-breed dogs with
M-mode echocardiogram from a male Maltese with advancing CMVD are considered prudent because of their
advanced mitral valve regurgitation and congestive heart tendency to develop reduced myocardial function sooner.
failure. Note vigorous septal and left ventricular posterior Routine preventative healthcare should be continued, includ-
wall motion (fractional shortening = 50%) and lack of mitral ing heartworm disease prophylaxis, vaccinations, dental
valve E point–septal separation (arrows).
prophylaxis, etc. Concurrent medical problems should be
identified and managed as appropriate. Owner education
about the disease process and early signs of heart failure is
(TDI) measurement of lateral or septal annulus veloc- important.
ity help characterize LV diastolic function and LV filling Clients should be taught how to assess their pet’s resting
pressure. Discrimination of disease-induced mild diastolic (ideally, sleeping) RR to establish that individual’s normal
dysfunction is difficult, because many older dogs have baseline, and, as the disease advances, to help screen for pos-
the delayed relaxation pattern of mitral inflow (E/A<1). sible early signs of decompensation (see Chapter 3, p. 73 and
However, pseudonormal and restrictive inflow patterns are Box 3.2, p. 74). No specific cardiac therapy currently is rec-
common in dogs with advanced CMVD, especially those ommended for dogs in stage B1. For dogs with elevated BP,
with CHF. Mitral E velocities well over 1 m/s are common an ACE inhibitor (ACEI) is recommended to maintain
with advanced CMVD. However, mitral inflow pattern by normal arterial pressure and cardiac afterload. Normal exer-
itself is not a sensitive correlate for identifying high LA pres- cise and activity, as well as a normal diet, can be maintained
sure and pulmonary edema. Nor is the ratio of early LV at this stage although avoiding high-salt foods and treats is
inflow to annular tissue velocity ratio, E/Ea (also expressed recommended. Extremely obese dogs could benefit from
as E/E’ and E/Em), useful for predicting LA filling pressure weight reduction during this preclinical stage; however, a
(or CHF) in dogs with CMVD. However, the early mitral mildly overweight state is not considered problematic and
inflow velocity to IVRT ratio (E:IVRT) is more useful in could be helpful later if chronic CHF therapy becomes
identifying elevated LA (LV filling) pressure in dogs with necessary.
MR. This index combines peak mitral E velocity (determined
mainly by LV filling pressure and relaxation) and IVRT STAGE B2
(dependent mostly on LV relaxation). An E:IVRT >2.5 has Dogs with measurable left heart enlargement but without
been proposed as a cut-off value for predicting CHF in dogs ever having developed clinical signs of CHF are in stage B2
with CMVD. CMVD. Monitoring and routine healthcare recommenda-
tions for these dogs are similar to those for stage B1, except
recheck frequency is increased to every 6 to 9 months, or
Treatment and Prognosis sometimes more often for markedly advanced disease. In
Goals of preclinical (stage B) CMVD management are addition to a thorough physical examination and BP check,
to delay the onset of CHF, and to identify and treat the thoracic radiographs and echocardiogram or NT-proBNP
early signs of decompensation before fulminant pulmo- are done to monitor progression; echocardiography provides
nary edema develops. For dogs that already have devel- more specific information about cardiac enlargement and
oped CHF (stage C), therapy is aimed at controlling signs function. Screening for concurrent medical problems also is
of congestion, enhancing forward blood flow, reducing advised. Home monitoring, as described for stage B1 dogs,
regurgitant volume, and diminishing excessive NH acti- should be continued with greater attention.
vation. Ultimately, the goal is to provide good quality of Pimobendan (Vetmedin) at the standard label dose cur-
life while extending survival time. Box 6.2 outlines treat- rently is recommended for dogs with stage B2 CMVD.
ment guidelines for CMVD based on level of disease Pimobendan has been shown to delay the onset of CHF
progression. (by a median of 15 months) and prolong survival without