Page 161 - Feline Cardiology

160 Section D: Cardiomyopathies

tolic function in the failing heart, exacerbate congestive
is debatable in cats and it can be given short-term to heart failure, or cause low-output (forward) heart failure
hospitalized cats for no longer than 2 days; the main that is evidenced by arterial hypotension. Cats that are
drawback appears to be a lack of efficacy rather than chronically treated with beta blockers for asymptomatic
adverse effects. HCM and then subsequently develop congestive heart
• Negative inotropic therapy including beta blockers and failure can be continued on atenolol, although the dose
calcium channel blockers may be used in some cats with
chronic heart failure but are not given in acute heart is often reduced by 30–50%. Beta blockers should be
failure unless there is a hemodynamically significant stopped, either temporarily or indefinitely, in the follow-
tachyarrhythmia. ing situations: the cat has bradycardia (HR ≤140) and is
• ACE inhibitors such as enalapril or benazepril may hypotensive, the degree of dyspnea precludes oral
Cardiomyopathies failure. Rather than starting as an emergency in-hospital medications. In the chronic setting, the use of beta
administration, or the cat is not able to tolerate oral
help provide adjunctive treatment in cats with heart
treatment, the ACE inhibitor may be started at home
blockers or calcium channel blockers in cats with HCM
once the cat is stabilized, eating and drinking, and
and heart failure is debatable since the largest multi-
hydrated.
center study to date in cats did not identify an improved
• Prophylactic anticoagulant may be started in cats with
high risk of arterial thromboembolism (ATE), including survival in cats with cardiomyopathy and CHF or arte-
rial thromboembolism treated with beta blockers,
those with spontaneous echocardiographic contrast, left calcium channel blockers, or ACE inhibitors, and a trend
atrial thrombus, history of prior ATE, or severe left atrial
dilation. toward decreased survival in cats treated with atenolol
(Fox 2003b). One hundred and eighteen cats were
enrolled in this study, including 57 cats with HCM and
37 cats with HOCM. Although no treatment improved
survival, there was a trend toward improved survival in
Outpatient treatment of symptomatic cats the enalapril group (p = 0.06) (Fox 2003b). The opinion
with HCM of many cardiologists is that some cats with CHF clini-
Cats with severe HCM may develop symptoms of cally improve when treated with an ACE inhibitor, and
dyspnea, tachypnea, exercise intolerance and lethargy, it should be used as adjunctive therapy along with furo-
anorexia, or syncope once heart failure develops. semide in all cats with heart failure.
Furosemide is the most efficacious and life-saving treat- Thoracic radiographs are essential to confirm the
ment to reduce pulmonary edema and slow accumula- presence of, and evaluate the severity of, heart failure in
tion of pleural effusion in cats with heart failure. cats that have clinical signs of tachypnea or dyspnea. In
Diuretics (furosemide) and ACE inhibitors are indicated cats with moderate or severe pleural effusion, thoraco-
for treatment of CHF due to almost any etiology except centesis should be done to immediately stabilize the cat
pericardial effusion and cardiac tamponade, so they prior to further diagnostic workup. Often a brief tho-
should not be withheld in animals that cannot be exam- racic ultrasound can be done to rapidly assess whether
ined by echocardiography. Treatment of symptomatic there is significant enough pleural effusion to require
cats with CHF due to diastolic heart failure caused by thoracocentesis. The cat is placed in sternal recumbency
HCM or other causes of increased myocardial stiffness with minimal manipulation or stress during the scan.
is aimed at reducing fluid accumulation (i.e., pulmonary Assessment of significant atrial dilation may also be
edema and/or pleural effusion) with furosemide and made during this initial brief ultrasound, which helps
additional chronic therapy with an ACE inhibitor. establish the likelihood of a cardiogenic cause of the
Cats in active heart failure rely on elevated sympa- pleural effusion. Thoracocentesis is done with the cat
thetic tone for maintaining, albeit decreased, cardiac typically in sternal recumbency. Ultrasound helps guide
output and blood pressure to remain alive. When beta the optimal site for thoracocentesis, where there is the
blockers are given in the setting of acute heart failure, most pleural effusion and furthest away from vital struc-
loss of the beta receptor stimulation may lead to further tures such as a severely dilated left atrium. Thoracocentesis
deterioration and worsened cardiac output and arterial is needed to physically remove substantial pleural effu-
hypotension. Therefore, treatment of cats with active sion, since diuretic therapy is not expected to mobilize
heart failure with a beta blocker is contraindicated the fluid quickly but is expected to lessen further fluid
unless there is a significant tachyarrhythmia such as ven- buildup. Often the best site for thoracocentesis is caudal
tricular tachycardia or supraventricular tachycardia with to the heart, at the level of the costochondral junction,
high heart rates (over 250 bpm). Massive tachycardic on the right side of the thorax. Unless the cat has life-
events (>250 bpm) adversely impact diastolic and sys- threatening dyspnea, the site is clipped and sterile prepa-