Page 282 - Clinical Small Animal Internal Medicine

250 Section 3 Cardiovascular Disease

Digoxin is commonly used to treat dogs with concomi- with damage of the endothelium that triggers the coagu-
VetBooks.ir tant atrial fibrillation in order to control the heart rate. lation process. IE requires bacteremia. The most com-
mon sources of bacteremia are discospondylitis,
There are no controlled studies in veterinary medicine
evaluating digoxin, but it is believed that its administra-
tion could improve clinical signs of heart failure in dogs. prostatis, pneumonia, urinary tract infection, pyoderma,
and intravenous catheters. Circulating bacteria can bind
In the author’s experience, most dogs can be managed to the coagulum and induce inflammation that leads to
using a combination of furosemide, ACEI, pimobendan, expression of integrins that further facilitate bacterial
and spironolactone. Treatment should be individualized adhesion to the damaged tissue. Some bacteria, such as
for each patient and the goal is to keep the animal free of Staphylococcus sp., might increase their ability to bind to
clinical signs of CHF for as long as possible. the coagulum through increased expression of microbial
surface adhesive molecules. Vegetative lesions contain-
The Dog with Refractory Heart Failure (Stage D: ing bacteria provide a protective barrier and obstacle to
ACVIM Consensus) antibiotic penetration. Moreover, bacteria can produce
Stage D includes dogs refractory to treatments for stage enzymes that lead to further tissue damage.
C. Many of these dogs also have right‐sided heart failure, The only cardiovascular disease associated with an
which leads to congestion of the gastrointestinal tract increased risk of IE is subaortic stenosis. Historically,
that can decrease absorption of oral medications. periodontal diseases have been thought to increase the
Providing furosemide by subcutaneous injection may risk of bacterial endocarditis, but an association has
help to restabilize the patient. Chronic use of furosemide never been demonstrated.
can also lead to furosemide resistance and it is likely that
many stage D patients develop this condition. In these Epidemiology
dogs the use of an alternative loop diuretic, such as
torsemide, may represent a valid alternative. Adding a Infectious endocarditis is a rare condition in dogs and
diuretic with a different mechanism of action such as a cats. According to published data, prevalence of the
thiazide represents another alternative. The goal in these disease varies from 0.005% to 0.09% in the dog. The
cases is to induce “sequential nephron blockade” and prevalence in cats has not been reported but IE is less
improve diuresis. Patients on high doses or combina- frequently noted in this species. A recent retrospective
tions of diuretics should have their electrolytes and renal study has suggested that IE is becoming more common.
function monitored closely. This might be attributed to the increased recognition of
Amlodipine at the dosage of 0.05–0.1 mg/kg q12h is the disease due to the availability of echocardiography.
listed in the ACVIM consensus statement as a possible Large‐breed dogs are more commonly affected. A review
treatment for dogs with stage D CHF in order to obtain a of published data shows that the mitral valve is most
more effective reduction in afterload and improve car- commonly affected (60%) followed by the aortic valve
diac output. Arteriolar vasodilation associated with the (29%). Both the aortic and mitral valves are affected in
use of this drug can lead to severe hypotension. It is, 5% of the dogs, whereas the pulmonic and tricuspid
therefore, recommended to uptitrate the dosage of valves are rarely affected in dogs (4%).
amlodipine and monitor the blood pressure in order to
avoid hypotension. In the author’s experience, intrave- History and Clinical Signs
nous vasodilators, such as sodium nitroprusside, can
also help resolve an acute episode of pulmonary edema. Clinical signs in patients with IE are various and nonspe-
cific. Many patients show clinical signs related to the
underlying systemic disease that produced the bactere-
Valvular Infectious Endocarditis mia. Analysis of published case series including 183 dogs
with IE showed that the most common clinical sign is
lameness (67%), followed by anorexia (55%), lethargy
Etiology and Pathophysiology
(55%), acute onset of respiratory distress (52%), and
Valvular infectious endocarditis (IE) is a severe acquired syncope/weakness (15%). Fever is reported in 48% of
valvular disease of dogs and cats that is frequently caused cases. Presence of a murmur is reported in only 55% of
by bacterial infections. The most common pathogens cases with a definitive diagnosis of IE. The reason for the
associated with IE in the dog and the cat are Staphylococcus relatively low prevalence of murmurs may be similar to
and Streptoccoccus sp. Recently, Bartonella sp. has been what has been previously described for murmurs in
associated with IE, and has been considered responsible patients with MMVD. Moreover, when only the aortic
for up to 28% of IE in the dog. Less commonly, IE has valve is affected, the murmur can be diastolic and
been associated with fungi and Rickettsia spp. IE starts difficult to recognize. The recognition of a new systolic