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no prospective randomized clinical trials in cats with HF evaluating pimobendan, but a recent retrospective case series suggest that it is safe at similar doses used in dogs.59, 60 A pharmacokinetic study in cats suggests that pimobendan may have a longer half-life in cats than dogs.61 In dogs, the onset of action and peak blood levels of pimobendan and its metabolite are reached within 1 hour of administration of a single oral dose. Because of its rapid onset of action, the author has found it to be very useful in the management of severe acutely decompensated HF. Pimobendan is given as soon as the clinician feels that the dog or cat can take an oral medication. Dose and frequency escalation are common with recurrent or refractory HF with good clinical response.62 Pimobendan is primarily eliminated in feces via bile (95%); only 5% of the drug and its metabolites are renally excreted, making it safe to use with concurrent renal disease and HF, which is common in older dogs with MVD.63 The addition of pimobendan allows lower doses of furosemide and ACE-inhibitors. Adverse effects are surprisingly few. Because of the human experience, there are concerns for proarrhythmic tendencies. These concerns have, for the most part, been greatly reduced by the canine clinical trials showing no increase in arrhythmias. Since the introduction of pimobendan, the use of digoxin in the management of canine HF has decreased dramatically. The most common scenario when one may use digoxin (Digitek), usually combined with diltiazem (Cardizem), is in the management of rapid atrial fibrillation in the setting of congestive HF either caused by DCM or MVD disease, without evidence of renal insufficiency. If patients with HF are unable to take oral medications and have signs of severe low cardiac output HF, dobutamine (Dobutrex) is recommended. Dobutamine is an IV adrenergic-positive inotrope with primarily beta-1 effects. The dosage ranges from 1 to 10 mcg/kg/min CRI, starting at a lower dose and titrating upward based on blood pressure and electrocardiogram (ECG) monitoring. Tachyarrhythmias are the main adverse effect. This drug is most useful in cardiogenic shock (eg, Doberman pincher with severe DCM, hypotension, and severe pulmonary edema). If concurrent atrial fibrillation is present, rapid IV digitalization is recommended before dobutamine to slow AV nodal conduction. Other therapeutic considerations in the management of patients with HF include possible thoracocentesis or abdominocentesis, bronchodilators, and antiarrhythmic agents (see next section on arrhythmia management). If large-volume pleural or abdominal effusion is present and causing patient discomfort, the most effective therapeutic maneuver is the removal of the fluid by centesis. The optimal site for thoracocentesis and abdominocentesis can be guided by ultrasound. Additionally, if concurrent airway disease is suspected, empiric bronchodilator therapy may be beneficial. Many small-breed dogs with advanced valvular heart disease may also have significant airway disease that can contribute to clinical signs. Additionally, some cats with HF may develop peribronchiolar edema with associated bronchoconstriction. Inhaled albuterol (ProAir HFA) is an easy-to-administer bronchodilator with mask and spacer chamber (AeroKat). Other useful bronchodilators are terbutaline and theophylline. Bronchodilators should be used cautiously, however, because they may promote tachyarrhythmias if administered at high doses. Treating the first episode of acutely decompensated HF is usually successful. A recent study showed an estimated 80% survival rate to discharge for dogs with acute HF that were admitted to a university ED in an urban setting.21 Once the diagnosis and initial urgent management of HF has been performed, a plan for continued management and monitoring should be formulated. The therapeutic plan will be tailored to the individual patient based on the pathophysiology of the HF and any concurrent disease. An important and often overlooked part of the successful emergency management of congestive HF is open communication with the owner regarding the emotional, practical, and financial ability to deal with the long-term management of the animal’s heart disease. Survival times for most dogs or cats in HF with treatment vary from 6 months to 1 year, depending on the underlying cause of the heart disease and comorbidities. Arrhythmias Arrhythmias can occur with a wide range of diseases and vary greatly in their clinical signs from asymptomatic to collapse, depending on the rate, frequency, and complexity of the arrhythmia and the severity of any organic cardiac dysfunction or other noncardiac diseases. Tachyarrhythmias are suspected on physical examination in emergently ill patients on cardiac auscultation because of either sustained or paroxysmal bursts of tachycardia, generally at heart rates of 150 to 300 beats per minute. An ECG is necessary to further characterize the tachycardia into a sinus tachycardia, a ventricular tachycardia (VT), or supraventricular tachycardia (SVT). Sinus tachycardia is a physiologic rhythm that originates in the sinus node and occurs in response to increased need for cardiac output or increased sympathetic tone. Cardiac and noncardiac diseases may result in either supraventricular or ventricular tachyarrhythmias. Noncardiac disease conditions, such as sepsis, pancreatitis, autoimmune hemolytic anemia, pheochromocytoma, gastric-dilation-volvulus, splenic disease (eg, neoplasia, torsion), and end-stage uremia, may result in supraventricular and ventricular arrhythmias in the absence of structural heart disease. Another electrical rhythm disturbance that can be seen in critically ill patients is accelerated idioventricular rhythm (AIVR). AIVR is an ectopic ventricular rhythm with a rate of 60 to 120 beats per minute. AIVR is thought to be a relatively benign arrhythmia requiring no treatment. Electrolyte disturbances, such as hypokalemia, hypocalcemia, hypomagnesium or hyperkalemia, and digoxin toxicity may cause myocardial ionic abnormalities and arrhythmias. Other cardiac causes of