Ventricular Septal Wall Dyskinesia in 2 Steller Sea Lion Pups (Eumetopias Jubatus)
IAAAM 1991
Dawn M. Smith, AHT; Laurie J. Gage, DVM

On August 20th, 1990 a Steller sea lion (Eumetopias jubatus) pup (SSL#9) was admitted to the Marine Mammal Center in Sausalito, Ca. He had been removed from the rookery at Ano Nuevo Island by a research team from the University of California at Santa Cruz after attempts to reunite him with lactating females failed. He presented with spasmodic episodes that appeared to be brought on by stress (especially restraint). The spasms were accompanied by a cardiac gallop rhythm. Once the restraint was finished the animal returned to normal activity within a minute. It is not known how long after the spasms stopped the animal's heart rate and rhythm returned to normal as unrestrained auscultation was not possible.

Due to the difficulty of obtaining good electrocardiograms on pinnipeds with the equipment available at the Center, it was decided that a sonogram should be attempted. The sonogram, done on August 26, 1990, showed a dyskinesia (an impairment of the power of voluntary movement that results in fragmented or incomplete movement if the heart) of the mid to apical ventricular septal wall. The videotape of the sonogram was sent to a veterinary ultrasound specialist. In his opinion, it did not appear that the dyskinesia was the cause the symptoms noted nor that it presented a life threatening situation. He requested a follow-up sonogram and a sonogram on a same-age conspecific for comparison as he had not seen any sonograms of sea lions previous to this.

The second sonogram, done on November 18, 1990, showed the same dyskinesia. The incidence of spasms had decreased by this time, with only very occasional occurrences, none of the severity seen in the first few weeks of hospitalization. The sonogram of the conspecific, SSL#7, taken from Ano Nuevo Island under similar circumstances on August 20th, 1990, showed a similar dyskinesia. This animal was totally asymptomatic. The availability of a small, juvenile California sea lion{Zalophus californianus}, CSL#1 168, and the similarity of the two species led us to do a sonogram on that animal as well to determine if otariids in general showed this type of cardiac movement. This animal demonstrated the very same dyskinesia. Attempts to perform sonograms on northern fur seal pups (Callorhinus ursinus) in rehabilitation at the Center have not been successful so we cannot say with certainty that this condition occurs in the three types of otariids we normally see. The combination of a very dense haircoat and very little body fat made imaging the fur seal difficult. The excitability of the species also reduced the amount of time we could restrain the animal for the procedure without causing hyperthermia.

Both Steller pups are of an age and size to make further sonograms difficult, if not impossible, without the use of anesthetic agents. The policy of the Center is to not use any anesthetic agent on a rehabilitator animal unless it is necessary for a diagnostic procedure. The fact that the original animal is not in distress at this time, coupled with the minimal direct value of the procedure to these animals means that we will not be able to follow the two animals' cardiac development further. We are presently attempting to determine who, if anyone, besides ourselves has done studies on otariids and if any were done, what their findings were. We are also consulting with a cardiologist regarding the possible significance of our findings. We look to other facilities to help us with this study. We would request that any facility with ultrasound capability consider doing similar studies so that we might determine if this actually is a normal movement of the ventricular wall for otariids rather than a true dyskinesia. We will attempt to do sonograms on as many appropriate cases as possible until there is a significant database to judge this on. As a study in progress we will attempt to obtain comparative studies on several phocids as well.

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Dawn M. Smith, AHT

Laurie J. Gage, DVM
Six Flags Marine World
Vallejo, CA, USA

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