Abstract

A 33-year-old geriatric, castrated, male California sea lion (Zalophus californianus), managed under human care, presented with exercise intolerance, lethargy, tachypnea and open-mouth breathing. Electrocardiogram (ECG) detected atrial fibrillation (AF) characterized by lack of P waves and irregular R-R intervals, with an elevated ventricular rate up to 200 beats per minute.^1,2 Echocardiography revealed no major underlying heart disease and mild valvular disease. Treatment was initiated with diltiazem, a calcium channel blocker, class IV antiarrhythmic drug. The treatment goal was to lower the ventricular rate or convert to sinus rhythm to prevent the deleterious effects of sustained tachycardia.^1-3 Given its novel use in a pinniped, a low dose was initiated at 60 mg diltiazem extended release (0.5 mg/kg orally every 12 hours). Monitoring was conducted daily using AliveCor® Kardia Mobile ECG and the dose was gradually increased every 3–4 days until the desired ventricular response rate was achieved. Additional monitoring was conducted twice weekly using 3-lead ECG and Polar® H10 chest strap heart rate monitor. At a dose of 180 mg (1.5 mg/kg orally every 12 hours), the ventricular response rate reached the desired range, averaging approximately 100 beats per minute. Clinical signs improved and no side effects were observed. AF was still present and the rhythm did not convert to a sinus rhythm; however, rhythm control has not been found to be superior to rate control in regard to preventing secondary cardiac changes.^4-6 Monotherapy with a low dose of diltiazem successfully managed tachycardia and associated clinical signs of atrial fibrillation in a California sea lion.

Acknowledgements

The authors thank all of the veterinarians, technicians, and trainers at the U.S. Navy Marine Mammal Program, National Marine Mammal Foundation, and San Diego Veterinary Cardiology for their assistance with this case.

* Presenting author
+ Student presenter

Literature Cited

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