After the completion of cardiac ultrasound studies in 2005 at Discovery Cove in Orlando and in 2006 at SeaWorld in San Diego, the physiologic parameters of the bottlenose dolphin heart can be defined. Based on these physiologic standards, the diagnosis of several cardiac conditions can be made. The lists of diagnoses that can be made with confidence include, but are not limited to, the following:
Hypertrophy of the ventricular walls
Dilatation of the atria and ventricles, including the grade
Systolic and diastolic dysfunction
Morphologic abnormalities of the valvular cusps and leaflets, including the form, location, and degree of abnormality
Morphologic variations from normal of the myocardium and endocardium, including the form, location, and degree
Cardiac examination in a dolphin is recommended in the following cases:
Cardiac examination is important to determine if a risk of genetic problems may occur with breeding. Examination can also reveal if breeding between two different delphinid species could lead to cardiac morphology concerns. The cardiac examination of a common dolphin/ bottlenose dolphin hybrid, revealed a heart size (chambers, walls, aortic diameter) typical of the common dolphin, even though the hybrid dolphin's weight was twice that of a common dolphin. The small heart size may be due to the common dolphin's gene pool. The myocardial tissue of the hybrid showed no evidence of pathology as a consequence of its small size. Further examinations are planned to observe if this apparently undersized heart will be able to maintain its function without secondary lesions, especially in the myocardium.
2. Infectious Disease
A dolphin that has experienced a systemic infection or significant toxemic event, should have a cardiac examination to determine if any change or pathology has occurred as a sequel to illness. It is known that toxemia and bacterial, viral, parasitic, or mycotic disease could lead to myocardial changes1,2, as well as changes of valve morphology. These changes could lead to valve insufficiency, with the potential of volume overload in the chambers and its consequences.
3. Rescued Animals
A cardiac examination in hospitalized, stranded animals is recommended to verify if myocardial changes are present. In rescued and stranded animals, myocardial changes are frequently observed and described.3,4,5,6
4. Routine Examination
Complete cardiac examinations of 22 bottlenose dolphins, one common dolphin and one Atlantic bottlenose dolphin-common dolphin hybrid were made in 2006 at SeaWorld San Diego. A one-year follow up examination of 10 Dolphins has been recommended for the following reasons:
Significant morphologic myocardial changes in one dolphin
Atrioventricular valve regurgitation in what the author considerers the upper physiologic range, combined with morphologic changes of the cusps, in six dolphins
Atrioventricular valve regurgitation above the physiologic range in one dolphin
Multiple changes of more than three parts of the heart in five dolphins
Periodic reexaminations are recommended as life history data is of interest and importance to better understand the significance of cardiac abnormalities over the life of the animal, and whether the observed changes are stable and compensated or progressive.
The authors would like to thank Sound Technologies Inc. for providing a Vivid-Cardiology Ultrasound Unit, the trainers at Discovery Cove Orlando, and Sea World San Diego for their time and dedication and the SeaWorld dolphins for their cooperation and patience.
1. Augier H, Park WK, C Ronneau. 1993. Mercury contamination of the striped dolphin Stenella coeruleoalba Meyen from the French Mediterranean coasts. Marine Pollution Bulletin 26 (6): 306-311.
2. Parsons ECM. 1998. Trace metal pollution in Hong Kong: Implications for the health of Hong Kong`s Indo- Pacific hump- backed dolphins (Sousa chinensis.) The Science of the Total Environment 214 (1-3): 175-184.
3. Bossard GD, Odell DK, NH Altmann. 1985. Cardiomyopathy in stranded pygmy and dwarf sperm whales. JAVMA 187: 1137-40.
4. Capelli R, Drava G, De Pellegrini R, Minganti V, R Poggi. 2000. Study of trace elements in organs and tissues of striped dolphins (Stenella coeruleoalba) found dead along the ligurian coast (Italy). Advances in Environmental Research, 4 (1): 31-42.
5. Turnbull BS, DF Cowan. 1998. Myocardial contraction band necrosis in stranded cetaceans. J. Comp. Pathol. 118: 317-27.
6. Cowan DF. Pathologist`s Report. Texas Marine Mammal Strandíng Network. 1-800-962-6625.