• Pre and post exercise electrocardiography using a treadmill
• Radiography
• 24-hour electrocardiographic monitoring (Holter monitoring)
• Laboratory work
• Angiocardiography
• Pacemaker implantation
• Medical management of atrial fibrillation
• Coil embolization of guttural pouch mycosis
• Measurement of cardiac troponin

ARRHYTHMIAS IN HORSES (ABNORMAL RHYTHMS)

Cardiac arrhythmias occur commonly in horses. The cause and the treatment vary widely depending on the underlying etiology and type of arrhythmia. An ECG is necessary to confirm the diagnosis and choose the appropriate treatment

ATRIAL FIBRILLATION

Atrial fibrillation is the most common rhythm abnormality that occurs in horses. It rarely requires emergency treatment. Fortunately, most horses have no underlying cardiac disease but come to the CUHA for exercise intolerance. There are two ways to convert atrial fibrillation to normal sinus rhythm: medical therapy with administering quinidine or electrical cardioversion. The Cornell College of Veterinary Medicine is one of a few veterinary schools that are currently performing electrical cardioversion.

VENTRICULAR ARRHYTHMIAS

There are many causes for ventricular arrhythmias in the horse. Ventricular tachycardia is either caused be severe systemic disease (intestinal disease; colic, and infectious disease) or underling heart disease (see myocarditis). If the heart rate is very fast, this can be life threating and emergency treatment is required.

HEART BLOCK

AV (atrioventricular) block can be a normal variation in horses and rarely requires treatment. Many horses have an arrhythmia called second degree AV block. This arrhythmia is very common and often goes away with trotting or exercise. Normally the heart beat is initiated by the part of the heart called the sinus node. The impulse conducts through the atria and to the junctional point between the atrial and the ventricles. The junction is known as the atrioventricular node or AV node, in short. In second-degree AV block the electrical impulse from the top chamber of the heart (atria) does not conduct to the bottom chamber of the heart (ventricle) because the AV node malfunctions. It is very rare for a horse to have advanced AV heart block that would require pacemaker implantation.

MYOCARDITIS (Inflammation of the heart muscle)

Some horses with ventricular arrhythmias or heart block may have underlying inflammation of the heart known as myocarditis. In these situations monitoring of the arrhythmia and other tests (e.g. echocardiography, troponin I,) are required. Often the cause of the myocarditis cannot be identified, but this inflammatory process can often be treated with medication.

“LEAKY VALVE DISEASE” OF OLDER HORSES
DEGENERATIVE ATRIO-VENTRICULAR (MITRAL AND TRICUSPID REGURGITATION) VALVE DISEASE

Clinical Population: This very common disease usually affects older horses

Characteristics: The most commonly affected of the four heart valves is the mitral valve, which separates the left ventricle from the left atrium. Normally this valve closes when the heart contracts. Normally, this closure prevents blood from going back into the atrium so that the blood goes to the body. When the valve leaks, the blood goes backwards into the left atrium. The flow of blood going the wrong way is called "regurgitation." Therefore, this disease often is called mitral regurgitation. (If the valve between the right ventricle and right atrium also is affected the term tricuspid regurgitation is used.) Eventually the left atrium enlarges followed by fluid accumulation in the lungs because of too much volume and pressure. The valve leaks because it has "degenerated." The normal structural integrity of the leaflets of the valve is lost.

Symptoms: Many horses with this condition can still be used for performance or riding. Clinical signs include exercise intolerance, coughing, trouble breathing, increased breathing rate, collapse, or weakness.

Diagnosis: Virtually all horses with clinically important mitral and tricuspid regurgitation or aortic insufficiency will have a cardiac murmur heard through a stethoscope. Veterinarians can hear a murmur long (months to years) before clinical signs are noticed. Echocardiography, or ultrasound, is an important diagnostic tool to fully characterize the structure and function of the valves. This test permits the examination not only of the muscle and valves, but also of the blood flow in the case of doppler echocardiography. Therefore, the changes to the heart are measured and the amount of blood "going the wrong way" can be semi-quantified. Other tests may be ordered to ensure that other body systems are functioning adequately for the clearance of the drugs that will be used to treat the disease process.

Treatment: Horses with only very advanced stages of the disease require treatment.

Prognosis: The prognosis depends on the severity of the disease, which is determined by when it is diagnosed. Many horses identified early live for many years, while others with heart failure may only live a few months. The diagnostic tests not only identify the condition, but also tell use the stage of disease in each horse.

How should an affected horse be monitored?
The frequency and intensity of the monitoring depends on each patient, the stage of the disease, the response to treatment, and the status of other body systems.

Your scheduled visit to the Cardiology Service at the Cornell University Hospital for Animals begins when you pull up to the circular driveway in front of the equine hospital. Please park your vehicle in the driveway, come into the reception area and check in at the front desk. After a small amount of paperwork, our licensed veterinary technician will help you unload and walk your horse to its assigned stall. 

Often times, you may leave your vehicle and trailer right in the driveway but, if the lot is full, the receptionist will provide you with a parking pass and directions to nearby longer-term parking where overnight parking for trucks and trailers is also available.

After your vehicle is parked, a senior veterinarian, veterinary resident ask you questions about the horse's past medical, surgical, travel and vaccination history and current health. They will work together to conduct an examination of your horse. Students observe and participate in this examination, which is invaluable to their education and development. We appreciate your patience and understanding in allowing these future veterinarians to interact with you and your horse.

After the physical examination, our veterinarians will discuss their findings and treatment options, including cost. Together, you will develop plan for further diagnosis and treatment of your horse. 

In most cases, you will be asked to leave your horse in the care of the student after this initial examination so that we may begin appropriate diagnostic testing, which commonly includes echocardiography, thoracic x-rays and electrocardiography immediately after exercise using a treadmill.
 

We frequently work as a team with veterinarians from other services to ensure your horse received the most comprehensive care possible. Given our busy schedule and our collaborative environment, you will most likely be asked to return in the afternoon to discuss our findings and recommendations . Please understand that our primary concern is the well being of your horse, and that although we will always strive to minimize the duration of your stay, we do not wish to compromise patient care. When you return, you will meet with the cardiologist or cardiology resident and the student working with your horse to discuss their findings and therapeutic recommendations. In many cases, therapy will be in the form of medication that you can administer at home. In some cases, your horse may require hospitalization for supportive care or diagnostics. In the event that your horse requires an elective interventional procedure, the rationale, logistics, and risks associated with the procedure will be discussed at this time, and the procedure can often be scheduled either at the time of discharge or within 24 hours of discharge.

Before leaving the hospital, you will receive a copy of the cardiology report, which outlines the findings and recommendations for management of your horse’s case. Your referring veterinarian will also receive a copy of this report via mail. You will also receive a copy of discharge instructions, which outlines our findings and recommendations. We will strive to make sure that we have answered any and all questions that you may have prior to your departure.

Dr. Sparks

The story begins in 2009, when a team of Cornell clinicians revitalized a young thoroughbred mare named Dr. Sparks, becoming one of the first academic veterinary teams to perform the coil-embolization procedure. A promising athlete, Dr. Sparks’ life had fallen in danger when she developed a growing infection in her head which damaged a major blood vessel and had the potential to create life-threatening hemorrhage.  

“The kind of infection Dr. Sparks had often leads to traumatic emergencies in horses,” said Dr. Norm Ducharme, medical director of Cornell’s Equine Hospital. “Once it erodes into an affected blood vessel, the only sure way to save the horse is through a minimally invasive interventional radiology procedure to stop the bleeding by closing off the vessel.”

Instead, Dr. Ducharme assisted the members of the cardiology and imaging faculty and staff used a novel approach with the Hospital’s state-of-the-art c-arm, a machine which shows radiographic images of the body in real time. This real-time imaging enabled the team to use minimally invasive techniques to guide equipment through the horse’s arteries to exactly the right spot for stopping dangerous blood-flow. With the machine’s help, they were able to prevent hemorrhage and also occlude the blood supply to the infection. Dr. Sparks soon regained her bright demeanor and was able to return to live a productive life.

Thanks to the recent acquisition of a new, more powerful c-arm, which uses less radiation to achieve clearer images of higher resolution, CUHA’s experts are better able to help horses with internal infections using precisely guided minimally invasive techniques.  This work also requires a unique combination of expertise from three different disciplines: surgery, cardiology, and imaging.

“The beauty of this procedure is that you can watch in real time as you guide equipment through the patient’s body,” said Dr. Marc Kraus, a CUHA cardiologist who participated in two of the three coil-embolization procedures performed at Cornell. “Few schools have tried this because it’s difficult to image a horse’s head in real time. With the improved c-arm, we are even better equipped with the kind of advanced imaging that is needed to perform this procedure to help equine patients.”

American College of Veterinary Internal Medicine
A non-profit board created to enhance animal and human health by advancing veterinary internal medicine through training, education, and discovery.