Introduction to Heart and Blood Vessel Disorders of Horses

Last Updated on March 29, 2022 by Allison Price

The cardiovascular system comprises the heart, the blood vessels (the veins and arteries), and the heart. The heart’s function is to pump blood. The right side of your heart pumps blood to your lungs. There, oxygen and carbon dioxide are added to your blood. The left side pumps blood to other parts of the body. There, oxygen and nutrients are delivered directly to the tissues and waste products are eliminated (such as carbon dioxide). The cardiovascular system of horses must be able to supply blood efficiently to all areas of the animal. It must also function properly during training or racing.

Horses’ cardiovascular system

The heart, a muscular hollow organ, is divided into four chambers in mammals. The myocardium is the muscular tissue. The upper chambers are located on the left and the right sides of your heart, and they are called the left and right respectively (plural form of atrium). The left and right ventricles are the 2 lower chambers.

A number of valves control blood flow through the heart. The atrioventricular and ventricles valves are between the atria, the ventricles. The semilunar valves lie between the heart, the aorta, and the pulmonary vein. Each ventricle contains an outlet and an inlet valve. The mitral valve is the inlet valve. The aortic va is the outlet valve. The tricuspid or inlet valve is located in the right ventricle. The pulmonary va is the outlet valve.

Heart and Blood Vessel Disorders

The venae and cavae are the largest veins in the body. They flow into the right atrium. The right ventricle relaxes and blood from the right atrium flows through the tricuspid to the right ventricle. The right ventricle fills up with blood. The right ventricle contracts, pushing blood through its pulmonary valve to the pulmonary vessels, which then lead to the lungs. Blood in the lungs absorbs oxygen and releases carbon dioxide. The blood flows into the left atrium through the pulmonary veins. The blood from the left atrium flows through the mitral valve to the left ventricle when the left ventricle relaxes. The left ventricle fills up with blood. The left ventricle contracts and pushes blood through the aortic vale into the aorta. This is the largest artery in our body. This blood transports oxygen to every part of the body, except the lungs.

Two parts make up a heartbeat: diastole, and Systole. The sound of the mitral or tricuspid valves opening is one half of a heartbeat. The sound of the aortic or pulmonary valves closing is the other half. The ventricles relax during diastole and fill with blood. They contract and pump blood to the body during systole.

Different hormones control the rate and force of heart contraction and the extent of narrowing and widening blood vessels. They also control the autonomic nervous systems, which is the part of the nervous that controls voluntary activity.

Heart Rate

The sinoatrial NODE is the tiny electrical current that causes the heart to beat. The contraction of muscle fibers within the heart is caused by rhythmic electrical impulses. When a horse is resting, the sinoatrial node discharges approximately 30 times per minute. Horses, as well as other large animals, have a slower heart beat than animals smaller in size (such as cats and birds). The heart rate rises with exercise. Maximum exercise can increase the horse’s heart rate by 250 times per minute.

Heart Sounds and Murmurs

Heart sounds result from the rapid acceleration and deceleration in blood and the resulting vibrations within the heart as a result of the blood’s circulation. You can hear them using a stethoscope. You can hear 4 different heart sounds in healthy horses. A heart abnormality could be indicated by an absence or abnormality in one of these sounds.

Heart murmurs can be heard from the heart and major blood vessels. They are usually caused by turbulent blood flow, vibrations of structures in the heart such as a valve or vibrations. The most common characteristics of murmurs are their timing (that’s when they occur in diastole or systole or continuously), intensity (that’s how easily they can be heard or with difficulty), as well as where they occur. Some murmurs are not indicative of a heart condition. Horses may have early diastolic or systolic murmurs if they are not suffering from heart disease. Healthy young horses may sometimes experience a short, high-pitched, squeaking early diastolic heart murmur.


Arrhythmias refer to abnormalities in the frequency, regularity, and site of heartbeat formation. Arrhythmias do not necessarily mean that you have heart disease. Arrhythmias are not necessarily indicative of heart disease and do not require any specific treatment. However, some arrhythmias can cause serious signs such as sudden death or loss of consciousness. Abnormal heart rhythms can be associated with many disorders. Arrhythmias can be described as a slow rate ( bradycardia), fast rate ( Tachycardia), premature beats, irregular rhythms, or pauses in the rhythm. Your veterinarian may recommend an Electrocardiogram to determine the cause of an abnormal rhythm.

Atrial Fibrillation is an arrhythmia that occurs frequently in horses. Atrial fibrillation is a condition in which the electrical current flowing through the atria does not coordinate, stimulation of the Atrioventricular Node is irregular and frequent, and the heart beat is irregular and rapid. A horse may have a normal resting heart rate. Although atrial fibrillation may be caused by heart disease, it is most common in horses with no underlying heart condition. Horses without underlying heart disease are unlikely to show symptoms during rest or moderate exercise. The arrhythmia might only be apparent when the horse is engaged in strenuous exercise. Your veterinarian will be able to determine if the arrhythmia is caused by heart disease. Your veterinarian might use medication or electricity to convert your arrhythmia into a normal rhythm.


The rhythmic expansion of an arterial can be felt by the fingertips during physical examination. The facial artery is located below the lower jawbone and is where horses feel their pulses. In healthy horses, a jugular pulse can be detected in the lower neck. However, excessive pulsing of the jugular can be observed in horses suffering from heart failure. An abnormal pulse can be absent, strong, or weak. This could indicate a particular type of heart disease.

Allison Price
Allison Price

I’m Allison, born and raised in San Diego California, the earliest memory I have with horses was at my grandfather’s farm. I used to sit at the stable as a kid and hang out with my Papa while he was training the horses. When I was invited to watch a horse riding competition, I got so fascinated with riding!