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Your Pet's Heart

Your pet's heart is responsible for pumping the blood that supplies oxygen and nutrition to all of the cells that make up your pet's body, and removes waste products from those cells so your pet can stay happy, healthy and active. In order to meet those needs, a medium-sized dog's heart has to pump more than a half-gallon of blood each minute, beating more than 100,000 times per day and resting only in between heartbeats! To accomplish this amazing task day after day, year after year, the heart has an extraordinarily strong, resilient muscle that is wrapped around its four chambers; four valves that ensure that blood moves in one direction only; and its own electrical system that stimulates the muscle to contract in an organized, efficient way at a heart rate that delivers the amount of blood needed to supply enough oxygen and nutrients to fuel all your pet's activities.

Heart Disease

Heart disease is relatively common in both dogs and cats. Current estimates suggest that about 10% of dogs and approximately 15% of cats suffer from some form of heart disease. 

In dogs, the most common form of heart disease is a degenerative condition that affects the mitral valve. Called a number of names (endocardiosis, myxomatous valvular degeneration, chronic valvular heart disease), this disease is usually a chronic, slowly progressive disease that most often affects small breed dogs in their middle to later years. Male dogs are more commonly affected than females.  The disease causes a typical heart murmur, which often allows the disease to be recognized by veterinarians long before clinical signs are apparent. 

Primary heart muscle diseases are also a relatively common cause of heart disease in dogs. These diseases include dilated cardiomyopathy (the most common, occurring almost exclusively in large or giant breeds such as Doberman Pinschers, Great Danes and Wolfhounds, more commonly in male dogs), hypertrophic cardiomyopathy (a rare disease in dogs), and arrhythmogenic right ventricular cardiomyopathy (ARVC, a common disease in Boxer dogs).

Pericardial diseases, while not as common as primary valvular or heart muscle diseases, is a common cause of cardiac emergencies and collapse (more common in larger, often middle-aged to older dogs).

Congenital heart diseases (patent ductus arteriosus or PDA is the most common, followed by pulmonic stenosis [PS], aortic or subaortic stenosis [AS or SAS], malformations of the mitral and tricuspid valves [MVD or TVD], and ventricular or atrial septal defects [VSD or ASD]) are relatively common causes of heart murmurs in dogs less than a year of age. Some congenital heart defects may be complex, consisting of multiple combinations of defects, and some may not be associated with an easily detectable heart murmur.  Many dogs with even serious congenital heart defects have no clinical signs at the time of diagnosis, and many can live normal lives if their disease is corrected at this stage -- for this reason, it's important to check out any heart murmur in a young animal.

In cats, primary heart muscle diseases (cardiomyopathies) are the most common heart diseases, with recent data suggesting that hypertrophic cardiomyopathy (HCM) may affect up to 15% of the entire cat population. Dilated and restrictive cardiomyopathy (DCM and RCM), as well as arrhythmogenic right ventricular cardiomyopathy (ARVC) are far less common, but also occur with some frequency in cats. 

Pericardial disease is a much less common primary finding in cats than it is in dogs. 

Essentially the same congenital heart diseases affect cats as affect dogs, however they are somewhat less common, and PDA in particular is less frequently observed in cats.


Heart Failure

Heart failure means that the heart is unable to pump enough blood to meet the body's needs for oxygen, nutrition and waste removal. Usually, the loss in pumping capacity is a symptom of an underlying heart problem, most commonly a leaking or narrowed heart valve or weakened heart muscle. Heart failure can also be caused (or worsened) by problems with the heart rate or rhythm, or by abnormal "plumbing" connections that can develop as a result of birth defects, either inside or outside of the heart. In companion animals, unlike people, heart failure is only rarely caused by blockage within the major arteries that supply blood to the heart itself (coronary artery disease), and "heart attack" (myocardial infarction) is a relatively rare occurrence in dogs and cats.

Although the term heart failure may sound like the heart suddenly stopped beating, heart failure usually develops slowly - often over years - as the heart gradually loses its pumping ability and works less efficiently. The severity of heart failure depends on how much pumping capacity the heart has lost, and what disease or process has caused the loss. Animals generally lose some heart pumping capacity as they age, but in companion animals, heart failure is rare unless some disease process severely damages either the heart valves or the heart muscle.

Early in the course of some heart diseases (e.g., chronic valvular disease, some forms of cardiomyopathy and some congenital heart defects), the heart may still be able to pump efficiently enough that the disease may have little apparent effect on the animal's lifestyle. If the progress of those heart diseases is allowed to continue unchecked, heart failure occurs, eventually interfering with even simple daily activities and devastating the pet's quality of life or causing sudden death.

Early diagnosis can provide a significant window of opportunity for effective treatment to alter the progression of heart disease, and most pets -- even those with clinical signs caused by incurable heart diseases -- can lead fuller, more active and happier lives with appropriate therapy.

Call the Cardiology Care Network Hotline tollfree at 888-962-7763 for answers to any questions that you have about your pet's heart disease, or to schedule an appointment through the NCSU Heart Failure Program. The Cardiology Care Network Technician is available between the hours of 9AM - 5PM Monday - Friday; Outside of regular business hours, emergency assistance is available 24 hours / day, 7 days / week through the NCSU-VTH Emergency service (phone 919-513-6911).

Sponsored by an educational grant
from Boehringer Ingelheim Vetmedica, Inc.