A horse's heart may be the most important muscle in its entire body. As the pump for the cardiovascular system, which includes the heart and a closed system of blood vessels called arteries, veins, and capillaries, it is responsible for the rapid delivery of nutrients and oxygen to all of the horse's tissues and organs. In addition, the cardiovascular system plays a crucial role in the elimination of waste products, distribution of hormones, immune response, blood clotting, and body temperature regulation.

Heart disease can affect horses of all ages and breeds. It can be congenital (present at birth) or acquired (developed later in life). The most common abnormalities involve the valves and muscle of the heart. Cardiac problems can manifest clinically in different ways, including poor performance, exercise intolerance, presence of a heart murmur, irregular heartbeats, distended veins, peripheral swelling, poor growth, weakness, or collapse.

The most frequently diagnosed cardiac abnormalities in equine medicine include congenital anomalies, degenerative or infectious valvular diseases, diseases of the muscle or external envelope of the heart (pericardium), congestive heart failure, and arrhythmias.

The importance of the heart cannot be overstated and any disease affecting it should be promptly diagnosed and monitored carefully. In-depth evaluation of horses suffering from heart disease typically requires advanced and accurate diagnostic aids to determine the underlying problem and to recommend appropriate treatment.

The internal medicine group at the Marion duPont Scott Equine Medical Center provides cutting-edge diagnostic and therapeutic services for horses affected with cardiac disease. When referred to our practice, a complete cardiac evaluation will be conducted, and will include a physical examination to determine the heart rate and rhythm and to detect the presence of heart murmurs, a resting electrocardiogram (ECG) to examine the electrical activity of the heart, and sometimes radiographs (x-rays) to examine the size and shape of the heart.

A complete cardiac ultrasound evaluation (echocardiogram) will also be performed to examine the valves, muscle, and heart function. The echocardiogram uses different echocardiography techniques to examine the size, structure, and shape of the heart in motion. Color-flow ultrasound and other Doppler technologies are also used to evaluate speed and patterns of blood flow within the heart and large vessels connected to the heart such as the aorta and pulmonary artery.

With digital image storage of the echocardiogram evaluation, the clinicians can easily review cases and follow their progression over time. Archiving of the cardiac examinations also allows the clinicians to share this information with referring veterinarians and to use the material for teaching purposes.

Other diagnostic tools available at the Equine Medical Center allow the clinicians to acquire continuous electrocardiographic recordings over one or more 24 hour periods. These tools are frequently used with critically ill patients for identification and monitoring of infrequent arrhythmias, quantifying the severity of an arrhythmia, or for evaluation of the efficacy of drug therapy.

In addition, horses are often referred to our institution for poor performance. Although musculoskeletal and respiratory system diseases are more common causes of reduced athletic ability, certain heart conditions can also lead to the development of exercise intolerance. In some cases, an exercise test is crucial for the detection of exercise-induced cardiovascular dysfunction. Electrocardiography using a radio telemetry unit can be performed during a high-speed treadmill examination or an under saddle evaluation to determine the heart rhythm during exercise. A functional assessment of the heart can then be performed in the immediate post-exercise period with echocardiography.

Our medicine group strives to maintain the health of horses with heart disease as well as to achieve the best quality of life possible for them. Appointments for cardiology consultations are made on an outpatient basis. Emergency receiving is also available for patients with acute and more severe cardiac conditions requiring immediate attention. Please do not hesitate to call 703/771-6800 to schedule a consultation or to inquire about the cardiology services offered at the Marion duPont Scott Equine Medical Center.

Dr. Desrochers is a clinical assistant professor in equine internal medicine at Virginia Tech's Marion duPont Scott Equine Medical Center. She can be reached at desroann@vt.edu. To view her online profile, visit www.equinemedicalcenter.net.