Medina Spirit Necropsy: Cause of Death “Undetermined”

[Wandering Eyes]

The cause of GI Kentucky Derby winner Medina Spirit's (Protonico) sudden death on Dec. 6 at Santa Anita remains undetermined, according to the findings of a necropsy on the horse.

In a news release issued in tandem with the necropsy report, the California Horse Racing Board (CHRB) stated that a “definitive cause of death was not established despite extensive testing.”

According to the CHRB news release, “Omeprazole (an anti-ulcer medication) and furosemide (aka Lasix, a diuretic) were detected in blood and urine samples consistent with the medication report filed with CHRB by the attending veterinarian. No other drugs, heavy metals (including cobalt), or toxicants were detected.”

According to the necropsy report, Medina Spirit's thyroxine levels were below normal reference limits, and that microscopic changes in various tissues were mild and did not suggest a specific cause of death.

“The swollen lungs and foam in the trachea (windpipe), enlarged spleen, and congestion and mild hemorrhages in other tissues seen on the postmortem examination are common in horses dying suddenly, and are compatible with, but not specific for a cardiac cause of death,” the CHRB news release states.

The necropsy was performed at the California Animal Health and Food Safety (CAHFS) San Bernardino laboratory, by a team who form part of the diagnostic laboratory system of the University of California-Davis (UC Davis) School of Veterinary Medicine.

The Bob Baffert-trained Medina Spirit collapsed and died after a scheduled workout on Dec. 6 at Santa Anita.

Medina Spirit's death triggered a wave of international headlines, not only because the horse faces possible disqualification from the Derby after a post-race sample tested positive for betamethasone, but also because seven Baffert trained horses infamously died suddenly during training or racing between 2011 and 2013.

As highlighted in this TDN article from 2018, however, a host of unknowns typically surround instances of sudden death in racehorses—a term that comprises many different causes, not simply issues related to the heart.

Sudden death includes massive bleeding in the lungs or abdomen, fractures of the skull or neck, and hemorrhaging from a pelvic fracture-all these injuries can prove swiftly fatal in a manner that, outwardly, resembles a cardiac issue.

Even when post-mortems are performed, when it comes to sudden cardiac death, oftentimes there are no lesions, ruptured arteries or damaged heart tissue that pathologists can point to with authority and say this or that caused the heart to stop.

What's more, sudden deaths happen extremely rarely.

In a 10-year period between 2007 and 2017 in California, 8.2% of all training and racing related fatalities were sudden deaths. So, what are the possible causes of so-called equine heart attacks? Answers aren't always easy to come by.

This comprehensive 2011 international review study points out that pathologists were only able to make a definite diagnosis in 53% of cases, a presumptive diagnosis in 25% cases, with 22% of cases left unexplained.

Indeed, rupture of the aorta-the largest artery in the body-is “anecdotally thought to be a common cause of exercise-related sudden death in horses,” but that it occurs in only 1% of cases, the study found.

There are other possible causes. Unlike human heart attacks due to clogged arteries, the sheer size of the equine heart makes them susceptible to electrical irregularities, like arrhythmias—an irregular heartbeat—and heart murmurs, the presence of irregular heartbeat sounds.

Experts point to a possible connection between the use of substances like clenbuterol, calcium, magnesium and cobalt—those that can alter equine cardiac muscle—and sudden cardiac death. But that connection hasn't been made definitively.

What's more, there have been efforts to try to identify a possible connection between certain genes in horses and a higher susceptibility towards cardiac problems. But again, this is a sphere of research with a lot more leg-work needed.

This story will be updated.

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