This article is a single center, 17-year retrospective study on the use of esmolol to control tachycardia in 22 dogs and 6 cats. Esmolol was used primarily in animals (22/28; 19 dogs and 3 cats) diagnosed with supraventricular tachycardia (SVT) or sinus tachycardia (ST); other diagnoses included atrial fibrillation (1; 1 dog) and ventricular tachycardia (5; 2 cats; 3 dogs). Administration was either as a bolus (13), bolus plus CRI (14), or a CRI (1).
Tachyarrhythmias were separated into those occurring from a cardiac disorder (7) or those from a noncardiac disease or source (21). Within these groups, animals were identified by initial rhythm diagnosis and underlying disease process. Arrhythmias in the cardiac group were varied with SVT (3), atrial fibrillation (1) and VT (3) present. In the non-cardiac group SVT/ST predominated (19) with the remaining 2 animals presenting with VT. Looking a bit closer, dilated cardiomyopathy (2), hypertrophic cardiomyopathy (4) and myocarditis (1) were the disorders present in the cardiac group. In the non-cardiac group, 12 animals were diagnosed with neoplasia (7) or inflammation/other (5) and 9 with a toxicity. Of those 9, 4 had albuterol toxicosis, 2 amphetamine toxicosis and 3 chocolate toxicosis.
Esmolol, a Beta1 receptor antagonist, is useful as a cardioselective antiarrhythmic due the rapid onset of action (< 10 minutes) and short half-life (15 minutes) in dogs. The rapid metabolism limits long term problems should adverse reactions such as bradycardia occur. The authors also state that it may be used in conjunction with another antiarrhythmic drug without worrying about a drug-drug reaction should esmolol be ineffective.
Treatment success included a reduction in heart rate and survival to discharge. The heart rate of 13/28 animals decreased by > 20% in 13/28 animals (average decrease of 48% +/- 18%). Decreased rate reduction occurred 11 animals at 1 hour and 2 animals by 2 hours. Nineteen animals survived to discharge. There was no correlation between treatment success and species nor between treatment success and initial rhythm diagnosis.
Esmolol has been used successfully in humans with caffeine, cocaine, and theophylline toxicosis. In this study, all 9 animals with toxin induced tachyarrhythmias survived. The authors suggest that esmolol should be considered in cases where the potential toxin is known to cause sympathetic overdrive or when pain, hypovolemia and other causes of tachycardia have been ruled out. They recommend that it be used cautiously in patients with a pheochromocytoma or ventricular tachycardia.
Two pearls for clinical use:
- The authors separated the data both by cardiac and noncardiac sources of the tachyarrhythmias and further by the underlying rhythm and by the underlying cardiac disease and underlying noncardiac disease.
- The article provided baseline knowledge on tachyarrhythmias and when esmolol may be used most effectively.