Dr. Byars--Pericarditis Becoming More of a Problem

By Kimberly S. Graetz

While the numbers are nowhere near those associated with early fetal loss and late gestation pregnancy loss, there is a pattern appearing with horses developing pericarditis (fluid in the sac around the heart), said Dr. Doug Byars, a specialist in internal medicine at Hagyard-Davidson-McGee's medicine unit in Lexington, Ky. At the industry meeting on Thursday, May 10, he reported that there had been 20 cases of pericarditis at Haygard's and Rood and Riddle Equine Hospital in the past week.

On Saturday morning, May 12, Byars reported that eight cases of pericarditis had been admitted to his clinic on Friday. Affected horses have ranged in age from young foals, to yearlings, to broodmares. Both sexes have been affected.

Byars said there are other things that are going on, like higher than normal infections after orthopedic procedures that indicate lowered resistance (compromised immune system), but "none are enough of a pattern to jump up and slap you," he said. "The pericarditis is in slap mode."

He said when veterinarians begin to see increasing numbers of a problem--such as with the red bag presentations of foals and the early fetal losses--it indicates a pattern is being established. Byars predicted that in the next three to four days, the industry will see more pericarditis cases.

He said while this is a significant problem, none of the treated horses has died. Since being alerted to the potential for pericarditis and recognizing early symptoms, veterinarians and farm managers are paying close attention to horses which seem to be lethargic or have symptoms that look like pneumonia. Byars said veterinarians are checking heart rates on some of these horses that seem to have a general malaise or appear to be getting a pneumonia and are hearing a muffled heart beat. This is because of the fluid accumulating in the sac around the heart.

Pericarditis with effusion--or a crushing of the heart because of fluid compression--is called tamponade. Dorland's Medical Dictionary expands a bit farther in saying that cardiac tamponade is acute compression of the heart caused by increased intrapericardial pressure due to the collection of blood or fluid in the pericardium from rupture of the heart, penetrating trauma, or progressive edema.

Treatment consists of intensive medical and physical care that might include draining the fluid from around the heart.

While none of the treated horses has died and all seem to be
responding to treatment, there is a worry about the future of these horses. The pericardium appears thick on ultrasound exam, said Byars. "So we must be careful of the pericardium scarring down and the problem becoming constrictuve pericarditis." Constrictive pericarditis results when the heart can't expand. It has the same clinical signs of heart failure as effusive pericarditis (when the fluid is there), but there is not much that can be done to treat it. The pericardium (sac around the heart) becomes scarred and doesn't let the heart expand normally, thus it can't function to move blood through the body.

"We can't do much about this problem in horses," said Byars. "I don't know of a successful pericardectomy (full or partial removal of the pericardium) in the horse. But who knows, we might get good at it in the next month or so."

Byars said that during these past couple of weeks, veterinarians and farm managers have been proactive in attempting to help the affected horses, even though a definitive cause isn't known. "I think from the beginning we've been on target to home in on this. Even though we don't know exactly the cause, we know quite a bit about medications and care and other syndromes that are similar to what we are seeing to be able to help these horses."

Other, non-specific problems being seen in the field that might or might not be related to the fetal/foal loss and pericarditis are oral ulcers, lameness, laminitis, fevers, and colitis. Some of these are to be expected normally with a large group of horses, and it will take time to tell if any or all of these other symptoms are connected with the initial problem of pregnancy loss.