Page 159 - Small Animal Internal Medicine, 6th Edition

CHAPTER 6 Acquired Valvular and Endocardial Disease 131

the intrapericardial bleed is modest and the dog appears hypotension is avoided. If spironolactone or another diuretic
relatively stable, conservative management might be success- is also being used, it should be reduced or discontinued,
VetBooks.ir ful. This involves cage rest, BP support, continued CHF depending on the level and progression of azotemia. Like-
wise, some cases can tolerate a slight decrease in furosemide
therapy, and removal of a small volume of pericardial fluid
only if required for signs of tamponade. Over time, the
monitoring (RRR and other signs) is required. Alternatively,
rupture could seal and pericardial blood would be reab- dose without precipitating pulmonary edema; however, close
sorbed. For dogs with echo evidence of an intraluminal the dose or frequency of ACEI could be decreased. Increas-
thrombus in the LA, there is presumably increased risk for ing pimobendan to q8h dosing also might help by improving
arterial thromboembolism (ATE). However, it is unclear renal perfusion. It is important to verify that the patient does
whether the benefit of antiplatelet therapy to reduce ATE not have a treatable underlying disease that may be affecting
potentially outweighs the risk of worsening intrapericardial renal function, such as ascending urinary tract infection.
bleeding, if a full thickness tear is present or develops. Dogs Mild azotemia can be acceptable as long as the patient feels
that survive are prone to another LA tear. good and is eating well. Electrolytes should be monitored. If
the azotemic patient is receiving digoxin, serum concentra-
CHRONIC AIRWAY DISEASE tions should be monitored more often to avoid toxicity. The
Chronic bronchitis and collapsing trachea are common in digoxin dose may need to be reduced or discontinued.
older small breed dogs. Associated signs are sometimes dif-
ficult to differentiate from CHF signs. At home, RRR moni- Prognosis
toring, changes in exercise tolerance and activity level, and The prognosis for dogs with CMVD can be quite variable.
thoracic radiographs are helpful in this regard. For dogs with Most dogs remain in a preclinical stage for years, and some
a new or worsening cough, especially a dry honking cough, never develop CHF. The median survival time for dogs with
that maintain normal RRR at home, empiric therapy (e.g., more advanced (stage B2) disease could be slightly more
antibiotic trial, bronchodilator, and finally antiinflammatory than 2 years. Although some suggest that median survival
doses of glucocorticoid) or further diagnostic testing can be times in dogs with moderate CHF might range from about
offered (e.g., radiographs with airway fluoroscopy, tracheal 1 to 3 years, the therapy used, complications that develop, or
wash or bronchoscopy with bronchoalveolar lavage, and even breed may influence this. However, for dogs with
culture of airway secretions). For persistent dry cough in the advanced CHF, survival times between 6 to 9 months are
absence of pulmonary edema, a cough suppressant (e.g., probably more likely. Yet some dogs with advanced stage C
hydrocodone or butorphanol) can be helpful. This may only disease do well for many months, or even a couple of years,
be needed intermittently when the dog is having a “bad day” with appropriate therapy. Despite periodic episodes of CHF
of coughing. It is important that the owner continue to decompensation or other complications, quality of life can
monitor RRR and be alert to possible episodes of recurrent be good most of the time. Nevertheless, some dogs die or are
pulmonary edema. euthanized during the first onset of CHF. Estimates of cardiac
death from CMVD have ranged from around 40% to almost
ABNORMAL BLOOD PRESSURE 70% of cases. Nevertheless, management strategies for CHF
Systemic hypertension, although not caused by CMVD, can are becoming more effective in controlling clinical signs and
complicate its treatment. Because hypertension can exacer- increasing survival time. Factors that have been associated
bate MR and cardiac workload, BP should be checked at each with disease progression or worse prognosis include older
visit. If elevated, and if ACEI dose is already maximized, an age, male gender, more severe valve lesions and degree of
arteriolar vasodilator (e.g., amlodipine) is added. Care valve leaflet prolapse or MR, ruptured chordae, severe LA
should be taken to verify that the high BP readings are not and LV enlargement, reduced LV systolic function, and ele-
just related to excitement. vated natriuretic peptide levels.
Conversely, hypotension can occur with excessive dosing Risk factors for first onset CHF are mainly related to
of an arteriolar vasodilator, dehydration, persistent arrhyth- increased heart size and associated high circulating NT-
mias, and/or poor contractility. Although uncommon, LA proBNP concentration. One study identified NT-proBNP
rupture with cardiac tamponade causes acute and profound concentrations ≥1500 pmol/L, end-diastolic LV dimension
hypotension indexed to aortic root diameter (LVIDd:Ao) ≥3, and VHS
>12 v as independent risk factors for first onset CHF in stage
RENAL DYSFUNCTION B dogs with CMVD, with failure likely to occur within the
Impaired renal function is common in older dogs with subsequent 3 to 6 months. The rate at which heart size
CMVD; it can be difficult to manage when there are increas- increases has been observed to accelerate within the 6 to 12
ing congestive signs. The lowest effective doses of furosemide months before clinical CHF onset.
are used. Optimizing forward cardiac output also helps pre- Prognostic indicators of reduced survival after CHF
serve renal perfusion. BP should be monitored, and high onset also relate to left heart enlargement, and high circu-
levels managed as possible. An arteriolar vasodilator (e.g., lating NT-proBNP and cardiac troponin I concentrations,
amlodipine) added to standard therapy can help improve although a decrease in circulating NT-proBNP concentra-
forward cardiac output and renal perfusion as long as tion after CHF therapy is thought to be a positive sign. LA