Abstract

Elasmobranch cardiac anatomy and physiology have been well described;^1-6 however, cardiac disease has not been documented until recently where a leopard shark (Triakis semifasciata) at a public aquarium was diagnosed with dilated cardiomyopathy.⁷ Herein, an approximate 22-year-old male sand tiger shark (Carcharias taurus) is diagnosed with suspected congestive heart failure secondary to dilated cardiomyopathy with subsequent successful medical management. The shark initially presented with increased respiratory effort through increased mouth gape and buccal pumping, as well as focal, dependent, peripheral edema involving both claspers and base of the pelvic fins. Echocardiography revealed a heart rate of 20 beats per minute with a normal rhythm, atrial and ventricular dilation, and marked sinus venosus-hepatic sinus dilation within the cranial liver. Coelomic ultrasonography was unremarkable. Bloodwork including complete blood count, biochemistries, protein electrophoresis, and blood gas analysis was unremarkable except for a moderate anemia at 11%. Therapy for congestive heart failure was initiated with oral benazepril 0.5 mg/kg and torsemide 0.5 mg/kg three times weekly, but after six months of therapy with dosage increases, clinical and echocardiographic signs of suspected congestive heart failure progressed—particularly the dependent edema that now involved most of the ventrum from the caudal peduncle cranial to the pectoral girdle. Pimobendan 0.5 mg/kg orally was added to the therapeutic regimen, but then was increased to 0.8 mg/kg after minimal improvement echocardiographically after three weeks of therapy. After three months of pimobendan, clinical signs improved with reduction in respiratory effort, near resolution of dependent edema, and improvement of anemia. Cardiac size and function improved on echocardiography, with a reduction in both end-diastolic atrial and ventricular inner diameter, increase in atrial and ventricular fractional shortening, and reduction in sinus venosus-hepatic sinus dilation. At the time of this writing, the shark has remained stable after eleven months of pimobendan with no adverse effects. Cardiac disease in elasmobranchs may be underdiagnosed, providing a necessity for standardizing ultrasound techniques and cardiac measurements for each species of elasmobranch managed within zoos and aquaria building upon the work by Lai et al.⁵

Acknowledgements

Much thanks and appreciation to the shark keepers and Aquatic Health veterinary team for their dedicated care of this shark and assistance with this case.

*Presenting author

Literature Cited

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