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Chapter 19: Congestive Heart Failure 297

used for chronic oral therapy of significant hypokalemia placed on anticoagulant therapy, and they can be done
(K < 3 mEq/l). Acid-base abnormalities are also common ∼2 weeks after initiation of therapy. Recheck echocar-
in cats with acute heart failure. Metabolic acidosis, diag- diograms can be done every 3–6 months for assessment
nosed by low bicarbonate concentration, may reflect low of atrial size, myocardial function, spontaneous contrast
output heart failure causing poor tissue perfusion and or intracardiac thrombus, or pulmonary hypertension.
lactic acidosis. Concurrent low venous oxygen partial Progressive, severe atrial dilation despite medical therapy
pressure (PvO 2 < 30 mm Hg) is consistent with poor indicates that the patient may be at risk of developing
tissue perfusion and increased tissue extraction of refractory heart failure. Myocardial failure may develop
oxygen. Therapeutic targets are to improve contractility in some patients that initially had preserved systolic
and increase cardiac output. Respiratory acidosis (ele- function. Patients with myocardial failure are good can-
vated PCO 2 ) is an ominous sign of impending respira- didates for positive inodilator therapy with pimoben-
tory failure and the potential need for mechanical dan. Echocardiography is the test of choice to evaluate
ventilatory support for the fatiguing respiratory muscles. for development of pulmonary hypertension that may
Respiratory alkalosis is not uncommon in dyspneic or develop in animals with severe heart failure. Right ven-
tachypneic patients. Hyperventilation is triggered by tricular concentric and eccentric hypertrophy, right
hypoxia, stimulation of atrial stretch receptors, or pul- atrial dilation, pulmonary artery dilation, and increased
monary edema stimulating pulmonary nociceptive J velocity of tricuspid regurgitation (>3 m/s) are all con-
receptors, and it usually improves as the edema is cleared. sistent with the diagnosis of pulmonary hypertension.
Sildenafil (1 mg/kg PO q 8 h) may reduce symptoms,
Monitoring for Recurrent Heart Failure severity, and frequency of syncope, and reduce pulmo-
Blood pressure, radiographs, and blood chemistry are nary artery pressure in animals with significant pulmo- Congestive Heart Failure
the most essential diagnostic tests to monitor during nary hypertension (consider if right ventricle: right
acute and chronic heart failure therapy. Vasodilators atrial pressure gradient >55 mm Hg) (see Chapter 25).
(ACE inhibitors) in combination with other cardiac
medications such as furosemide and antiarrhythmic OUTCOME AND PROGNOSIS
therapy (atenolol or diltiazem) may lead to hypotension
and may necessitate reduction in dose or discontinua- Outcome and prognosis include the following:
tion. Atenolol and diltiazem are reserved for patients
with significant tachyarrhythmias because they may • Heart failure is an advanced stage of severe heart
worsen acute heart failure. Respiratory status may be disease.
simply assessed by monitoring resting respiratory rate • Diseases associated with the shortest survival once
and effort, while the cat is resting in the cage without heart failure occurs include idiopathic dilated cardio-
manipulation. Radiographs are useful to assess for per- myopathy, arrhythmogenic right ventricular cardio-
sistent pulmonary edema or pleural effusion after myopathy, and restrictive cardiomyopathy. Survival
diuretic therapy, and helps the clinician plan appropriate ranges from days to a few months.
diuretic doses during transition to chronic oral therapy. • Survival is widely variable in cats with concurrent
Assessment of hydration status by physical examination, hypertrophic cardiomyopathy and congestive heart
PCV/TS, and severity of azotemia or electrolyte derange- failure and ranges from months to 1.5 years or longer.
ments on blood chemistry are essential to form a treat- • Negative prognostic indicators for cats with heart
ment plan for chronic heart failure therapy. failure secondary to HCM include tachycardia at pre-
A respiratory log recorded by the owner is a simple sentation, (increased) age, and left atrial size.
and practical tool to monitor for recurrence of heart
failure. On a daily basis, the owner records the resting Survival in cats with heart failure is highly variable and
respiratory rate and effort, appetite, and clinical dependent on the etiology of the heart disease. Cats with
demeanor, and the clinician can review the log intermit- heart failure secondary to idiopathic dilated cardiomy-
tently during a phone consultation with the owner. A opathy, arrhythmogenic right ventricular cardiomyopa-
resting respiratory rate that is persistently ≥40 breaths/ thy, or restrictive cardiomyopathy tend to have very
min increases the clinician’s suspicion of ongoing heart short survival times and usually succumb within several
failure and may preempt a recheck or a trial increase of weeks to months (median survival time: DCM 11 days
furosemide dose with reassessment of the respiratory log (Ferasin et al. 2003), ARVC 30 days (Fox et al. 2000),
a week later. RCM 132 days (Ferasin et al. 2003)). However, survival
Recheck echocardiograms are useful in cats with of cats with heart failure secondary to HCM is highly
spontaneous contrast or intracardiac thrombi that are variable. Median survival times in two retrospective,