(This is an excerpt from an article by Lauren Gold, courtesy of Cornell University College of Veterinary Medicine)
Standardbred racehorse Hard Hitter came to Cornell University to see veterinary cardiologists Anna Gelzer and Marc Kraus last fall after uncharacteristically dropping out of a race in Saratoga Springs. He was diagnosed with atrial fibrillation, a condition that caused his heart to lose efficiency under stress. When stressed, he became short of breath and unable to run.
Doctors recommended internal electric cardioversion, a procedure to shock his heart back into normal rhythm. Cornell is one of just a few facilities in the country to offer the treatment; about a dozen horses have been treated so far — all with success.
In Hard Hitter’s case the procedure would take much longer than usual — and would lead to the discovery of a new technique.
Atrial fibrillation, in which the heart’s upper chambers (atria) quiver and cause ineffective heart contractions, is common in horses — as well as in humans with other heart ailments. In horses it usually occurs in otherwise healthy hearts.
Pasture horses can live full lives with atrial fibrillation. But afflicted racehorses in the past were treated with quinidine, an anti-arrhythmic drug that often causes severe side effects and doesn’t always work. For Hard Hitter and his generation of racehorses, though, cardioversion is a new, quick, relatively painless procedure — costing about $1,700 — that gets otherwise healthy horses back into racing shape in just a few weeks.
Hard Hitter would be given an internal shock via two catheters threaded through his blood vessels into carefully chosen spots in his heart. He would be under general anesthesia for the shock — but first he had to be awake and standing as doctors positioned the catheters.
And this is a tricky job: Gelzer and resident Sophy Jesty inserted two catheters fitted with shock-delivering coils into Hard Hitter’s neck, where his skin had been anesthetized. Kraus pushed an ultrasound receiver into the horse’s chest and on a screen watched one catheter make its way toward the heart’s right atrium and the other to just above the heart in the left pulmonary artery. The locations allow the current to reach the largest possible area of the atrial wall without affecting other regions of the heart.
The crew then lined the obliging horse up against the back wall of a green-padded stall. An anesthesiologist looped his halter lead and a rope tied to his tail over two hooks. Vet students lined up beside him, feet braced and hands out. The anesthesiologist administered a shot — and the 950-pound animal fell gently, backwards and down.
Gelzer administered the first shock to the heart: 100 joules. She and the team peered at the electrocardiogram (EKG) monitor — and shook their heads. Like many horses, Hard Hitter would require more than one shock.
A second try failed, and a third. The EKG wasn’t changing. The cardiologists consulted X-rays and ultrasound images, adjusted the positioning of the leads and tried again. Still no luck.
Then Gelzer had an idea: inject harmless saline solution through the catheters. This would provide contrast in the ultrasound imaging and better show the exact location of the leads. They gave it a try — and almost immediately they saw that one lead was in a little too far.
They repositioned the lead, tried again. And — voila: Normal sinus rhythm.
“We learn something new every time,” said Kraus (after cheers subsided). Gelzer’s trick now will be incorporated into standard protocol, he added.
As for Hard Hitter, he stayed overnight for monitoring, then hit the road back to Saratoga. And just a few weeks later, he was back in light training. Chances are 60 percent that the fix will be permanent.
Blogger’s comment: I love this story. Cornell’s reporter has skillfully taken us inside the surgery unit by making an otherwise anonymous patient into a real horse–and with a great name, no less. But moreover, the writer made the surgeons into real human beings who had something to learn from a horse who wasn’t worth a million dollars. Thanks, Hard Hitter and Cornell!