Atherosclerosis in older horses: what you need to know

What is atherosclerosis in horses?

Atherosclerosis is a process in which the walls of arteries become thicker and stiffer due to the accumulation of calcium, fat and connective tissue. In horses, this primarily affects the large arteries around the heart, the aorta and the vessels that supply the intestinal wall. The condition develops insidiously over many years and is rarely a problem at a young age. In horses older than 15 years, veterinarians regularly observe calcified vessel walls during post-mortem examinations — estimates suggest 30 to 50 percent of older horses are affected. The reduced elasticity of the vessels raises blood pressure and makes the heart work harder, which can eventually lead to heart failure or sudden internal bleeding.

Risk factors you can influence

Some factors are fixed — age and genetics — but a number of risk factors can be effectively managed:

• Obesity and excessive energy intake, especially in horses with PPID (Cushing's disease)
• Prolonged lack of exercise, for example due to injuries or paddocks that are too small
• Consistently high grain rations that cause insulin spikes
• Chronic inflammation such as laminitis or dental problems that go untreated
• Elevated cortisol levels due to stress or poorly managed Cushing's disease

Symptoms you can recognise early

Atherosclerosis rarely presents a single clear symptom. You usually see a combination of vague complaints that can easily be attributed to ageing. Look out for:

• Faster fatigue during or after riding, even with light exercise
• Irregular or elevated heart rate during auscultation (above 48 beats per minute at rest is a warning sign)
• Swelling of the lower legs due to reduced venous return
• Colic symptoms without an obvious dietary cause, possibly due to poor intestinal blood supply
• Pale or bluish mucous membranes as a sign of circulatory problems

Diagnosis: what does the vet do?

There is no blood test that directly confirms atherosclerosis in horses. The vet combines several examinations: a cardiac ultrasound (echocardiography) to assess heart function and vessel walls, an ECG when there are indications of arrhythmias, and blood tests to detect underlying conditions such as PPID or insulin resistance. Cholesterol is a less reliable marker in horses than in humans, but triglyceride and insulin levels reveal a great deal about the metabolic risk profile. An early baseline assessment — from as young as 12 to 14 years — gives you something to compare later measurements against. Save those results in your horse's EquiSight horse profile so that your vet can immediately review trends over the years.

Treatment and daily management

There is no medication that reverses calcification, but you can slow its progression and maintain a high quality of life:

• Regular, adapted exercise: 20 to 30 minutes of walking per day promotes circulation without overloading the heart
• Forage-based ration with minimal refined carbohydrates; have a nutritional plan drawn up by a certified equine nutritionist
• Weight control: aim for a body condition score of 4 to 5 on a scale of 9
• Pharmaceutical management of PPID with pergolide if that has been diagnosed
• Regular dental checks and hoof care to eliminate chronic sources of pain
• Twice-yearly cardiac check-ups for horses older than 18 years

EquiSight helps you track trends

Atherosclerosis requires a long-term perspective. In your horse's EquiSight horse profile you record weight measurements, body condition scores and blood test results, so you can monitor the trend yourself without having to keep every old piece of paper. Through EquiCoach you can easily ask a question such as 'What should I look out for in a 20-year-old horse with Cushing's and high triglycerides?' and receive practical background information straight away. Use the calendar to schedule twice-yearly cardiac check-ups and nutritional evaluations, so that nothing slips through the cracks.