Cardiology 

Cardiology is the diagnosis and treatment of diseases of the heart. There are a range of diagnostic tools available, including radiography, electrocardiography and echocardiography.

Radiography involves the use of X-rays to allow detection of cardiac enlargement, pulmonary hypertension (increased blood pressure within the circulation to the lungs) and in extreme cases, pulmonary oedema (fluid in the lungs).

Electrocardiography involves the use of electrodes attached to the skin over the heart and on the neck to detect the electrical activity of the heart. The cardiac rate and rhythm can be recorded at rest or during exercise onto a paper trace, or can be recorded over a 24-hour ambulatory period onto a tape. This allows arrhythmias and isolated or runs of abnormal beats to be detected and definitively diagnosed. This is particularly important in equine cardiology, as physiological arrhythmias are frequently detected in normal horses and these have to be distinguished from arrhythmias due to underlying cardiac or metabolic diseases that require medical therapy.

A portable ECG machine such as this can capture the rhythm of an exercising horse - this can be done in the field but is often done on a high-speed treadmill such as the one shown

Cardiac murmurs are also frequently detected in horses and ponies. They are the result of turbulence of blood within the heart, due to leakage to blood through closed valves or due to blood flow through an abnormal communication between two cardiac chambers or blood vessels. Murmurs vary in the  significance of their effect on the horse's well-being and performance - it is always wise to discuss the importance of any findings with your vet.

Echocardiography is the use of ultrasound to visualise the structure and function of the heart. 2D echocardiography allows cardiac chamber size and motility to be assessed. Colour flow Doppler ultrasonography allows blood flow within the heart, particularly across the valves, or abnormal communications, to be detected. 'M mode' ultrasonography allows valve motility and chamber contractility to be assessed. Thus the origin and therefore significance and prognosis of equine cardiac murmurs can be evaluated.

Ultrasound of the heart of a pony with degeneration of the aortic valve

Colour Doppler Echocardiograph of a pony with a 'hole in the heart'