Heart Disease In Dogs & Cats: What You Need To Know To Keep Your Pets Healthy

Heart disease in dogs & cats is more common than you might think – and it’s important to understand the basics of heart disease in pets. When you take care of your pet’s heart, along with other aspects of health, you help ensure quality of life and longevity.

Primer On Heart Disease In Dogs & Cats: What is the Cardiovascular System?

The cardiovascular system is responsible for pumping blood throughout the body, ensuring that oxygen, nutrients, hormones, and the medications we give are delivered to the tissues and organs of your pets. The cardiovascular system is composed of the heart and blood vessels.

Primer On Heart Disease In Dogs & Cats: How Does The Cardiovascular System Work?

The heart is a muscular organ with built-in electrical impulses that cause rhythmic contractions. These contractions pump blood into the arteries. The pulmonary arteries carry blood to the lungs to be oxygenated. This blood returns to the heart through the pulmonary veins, and the aorta carries the oxygenated blood away from the heart to the rest of the arteries in the body. Smaller vessels called capillaries deliver oxygen and nutrients from the arterial blood to tissues while collecting waste products. The veins collect blood from the capillaries and return it to the heart to start the cycle over again.

Primer On Heart Disease In Dogs & Cats: What Can Go Wrong?

Unfortunately, cardiovascular disease is a common finding in our dog and cat patients. Abnormalities in the rhythm or strength of the heart’s contractions, changes in pressure within the blood vessels, and/or structural changes within the heart and vessels all can be problematic. Congestive heart failure occurs when abnormal pressure in the cardiovascular system causes fluid to leave the blood vessels and accumulate in either the lungs or the body cavities, depending on the nature of the heart disease.

Primer on Heart Disease In Dogs & Cats: Heart Disease in Cats

In cats, the most common type of cardiovascular disease is called hypertrophic cardiomyopathy, or HCM. HCM is a disease in which the muscular walls of the left ventricle of the heart are abnormally thickened. This causes the space within that heart chamber to shrink, resulting in less efficient delivery of blood to the tissues. To compensate, the heart will beat faster, and blood pressure increases. Both cause stress to the cardiovascular system, eventually leading to structural changes in other parts of the heart and congestive heart failure. Structural changes to the left atrium may result in blood clots forming within it, and these clots can enter circulation and block important blood vessels. This disease is believed to be genetic and is particularly common in the Maine Coon, Ragdoll, Persian, and Sphynx breeds of cats.

High blood pressure, or hypertension, often is seen in cats secondary to either HCM, chronic kidney disease, or hyperthyroidism. Sometimes, high blood pressure can cause bleeding and retinal detachment in the eyes, resulting in blindness.

Primer on Heart Disease In Dogs & Cats: Heart Disease in Dogs

The most common cardiovascular disease in older, small-breed dogs is chronic mitral valve disease. Valves within the heart direct blood flow between its chambers, and the mitral valve lies between the left atrium and the left ventricle. With age, the valve may become thickened or misshapen, resulting in inappropriate closure. This allows blood to flow backward and puts strain on the left atrium and ventricle due to decreased efficiency. Structural and pressure changes within the heart and blood vessels may eventually lead to congestive heart failure. Mitral valve disease can be genetic and may also be seen in younger dogs. This heart disease is common in the Cavalier King Charles Spaniel breed.

Larger dogs more commonly develop dilated cardiomyopathy (DCM). In contrast to HCM, DCM causes the development of thinner, weaker heart walls. This results in an enlarged heart chamber that is too weak to contract normally. Poor contractility of the heart often leads to weakness, reduced ability to exercise, and—as is the case with other types of heart disease—congestive heart failure. Like HCM, most cases of DCM are genetic. However, we’ve discovered that certain types of grain-free dog foods may predispose dogs to DCM who otherwise would not develop this type of cardiovascular disease.

When either the frequency or the timing of the heart’s contractions is abnormal, this is called an arrhythmia. Many types of arrhythmias are seen in veterinary medicine, including atrial fibrillation, ventricular tachycardia, and atrioventricular block.

Congenital heart disease is also seen in dogs with patent ductus arteriosus (PDA) being most common. In PDA, a blood vessel that should close at birth remains open, resulting in a disruption in the normal pattern of blood flow.

Of course, heartworms are another important cause of cardiovascular disease. A previous blog post covered this in detail.

Primer on Heart Disease In Dogs & Cats: What are the Signs of Cardiovascular Disease In Pets?

Sometimes, there are no outward signs of early cardiovascular disease. Symptoms of heart disease can be varied but often include:

• Less tolerance for exercise
• Labored breathing
• Weakness

Primer on Heart Disease In Dogs & Cats: How To Detect & Diagnose Heart Disease In Pets

Regular physical examinations help us detect cardiovascular disease, even in asymptomatic patients. Auscultation (the action of listening to sounds from the heart, lungs, or other organs, typically with a stethoscope as a part of medical diagnosis) is an important first step. Valvular diseases and PDA often create turbulent blood flow in the heart that we hear as a murmur through the stethoscope. Arrhythmias also can be heard in this manner. Harsh lung sounds and rapid breathing may be signs of congestive heart failure, prompting further investigation.

If a murmur is heard, chest X-rays and an echocardiogram are recommended. Both can be scheduled at Alford Avenue Veterinary Hospital. Chest X-rays are used to assess the general appearance of the heart’s shape and size and to evaluate the lungs. Rapid point-of-care ultrasound is used to quickly assess the lungs for fluid and to make brief assessments of the heart, but a lengthier scan is needed to more fully diagnose heart disease.

An echocardiogram uses an ultrasound probe to evaluate the chambers, walls, valves, and contractility of the heart – which can generate far more information than can be determined from chest X-rays. Ultrasound uses sound waves to make images and is a noninvasive imaging technique. Before the echocardiogram, one or both sides of the chest will be clipped to remove hair. Your pet will then lie down on an elevated, padded table designed to allow for easy access with the ultrasound probe, and most pets tolerate scanning without the need for sedation. Images and measurements are used to determine a diagnosis and to decide whether medication is needed.

All our veterinarians can obtain and evaluate chest X-rays and perform point-of-care ultrasound, but echocardiograms are scheduled with Dr. Cooner.  In some cases, referral to a cardiologist is recommended. We facilitate these referrals and share all medical and imaging reports to ensure our patients receive the best care possible.

Think your dog or cat has heart problems? Schedule an appointment with Alford Avenue Veterinary Hospital to get started.