Page 413 - Feline Cardiology

Chapter 29: Which Drug for Which Disease? 437

• Arteriovenous fistula (coil embolization or identifica- Premature Atrial Complexes/Atrial Tachycardia
tion and ligation) (AT)/Atrial Fibrillation (AF)
• Ventricular septal defect (typically large) causing left- • After underlying causes have been identified and opti-
sided congestive heart failure (pulmonary artery mally controlled, including resolution of congestive
banding procedure) heart failure, consider atenolol (6.25 mg/cat PO q 12–
24h) if clinical signs are present (clinical arrhythmia
The small size of the feline heart makes it a poor categories 1 and 2) with AT or AF. Consider the same
candidate for both open-heart procedures and catheter- treatment in any of the 3 categories if AT or AF persists
based interventions. Partial or complete palliation may at a rate of >260 beats/minute for several consecutive
be achieved for valvular pulmonic stenosis through tho- minutes or more.
racotomy and instrument dilation. • Target is to obtain a perfusing rhythm, i.e., an ade-
For the other congenital malformations, including quate cardiac output, typically requiring a heart rate
ventricular and atrial septal defects, mitral and tricuspid of <260 beats/minute. If initial dose of atenolol is
dysplasias, and others, medical treatment generally is insufficient and the cat is not decompensated with
indicated only after clinical signs of decompensation active heart failure, the atenolol dose can be increased
have occurred (an exception could be beta blockade, to 12.5 mg/cat PO q 12h. Other treatment options are
such as atenolol 6.25–12.5 mg PO q 12h in cats to consider switching to sotalol (2 mg/kg PO q 12h)
with disorders causing marked pressure overload, or adding digoxin (0.01875–0.03125 mg/cat PO q
notably severe pulmonic, pulmonary artery, or aortic 48h) unless HCM is present.
stenosis):

• Congestive heart failure: see above Premature Ventricular Complexes/Ventricular
• Aortic thormboembolism: see above Tachycardia
• Syncope: see “Arrhythmias,” below
• Severe polycythemia (HCT >60% in the cat); in • After underlying causes have been identified and opti-
patients with right to left shunts) mally controlled, including resolution of congestive
• Phlebotomy (withdraw 10 ml/kg body weight, may heart failure, consider lidocaine (0.25–1 mg/kg IV) or
repeat later the same day) as needed q 3–8 weeks or esmolol (50–200 mcg/kg/min IV CRI) if patient is in
more based on clinical response; target HCT is clinical category 1 or 2 and showing signs of hemody-
60–68%. namic compromise (e.g., poor/absent pulse, depressed
• Anticoagulation is not recommended, due to bleed- mentation) at the time of examination. If such signs
ing disorders paradoxically associated with con- abate, or are not present (category 3), verify that
genital heart disease–induced polycythemia in underlying causes such as hypokalemia, hyperthyroid-
children. ism, and hypoxemia, are optimally managed and if so,
consider atenolol (6.25 mg/cat PO q 12–24h) if ven-
tricular rate is consistently >260 beats/minute for
several consecutive minutes or more.
ARRHYTHMIAS
Broadly, feline arrhythmias can be divided into the fol- The target is a perfusing rhythm, i.e., an adequate
lowing 3 clinical categories: circulation, typically requiring a heart rate of <260
beats/minute. If atenolol is insufficient at starting dose,
1. Those occurring in patients with compatible overt may increase the dose to 12.5 mg/cat q 12h or consider
clinical signs such as syncope/collapse switching to sotalol (2 mg/kg PO q 12h), or mexiletine
2. Those in which clinical signs are present but they may (e.g., 3 mg/kg PO q 12h) may be added but
or may not be caused by the arrhythmia pharmacokinetic/pharmacodynamic studies in the cat
3. Those discovered as an incidental finding in an oth- are lacking to support safety of such treatment. Which Rx?
erwise well cat

The first step is diagnosis of the specific arrhythmia, REFERENCES
which may require extended ECG monitoring/telemetry
if the arrhythmia is only intermittent. Treatment is Amberger CN, Glardon O, Glaus T, Hörauf A, King JN, Schmidli H,
dictated by the type and clinical severity of the Schröter L, Lombard CW. Effects of benazepril in the treatment of
feline hypertrophic cardiomyopathy. Results of a prospective,
arrhythmia. open-label, multicenter clinical trial. J Vet Cardiol 1999;1:19–26.