More than 10% of dogs will develop heart disease in their lifetime. Fortunately, veterinarians are equipped with a number of tools to detect, diagnose, and treat it.

Family veterinarians are equipped to detect early signs of many heart diseases. Veterinary cardiac specialists offer cutting edge diagnostics and treatments that have greatly increased quality of life and survival times with affected dogs.

“A board certified veterinary cardiologist has gone through at least four years of additional training and a vigorous examination process, says Steven Rosenthal, DMV, Diplomate, ACVIM (Cardiology), of Cardiac Care for Pets. “They offer a higher level of expertise in the physical exam and cardiac diagnostic skills to help formulate treatment, monitoring, and potentially interventional plans for heart disease.”

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What Is Heart Disease and Heart Failure?

Heart disease is defined as any abnormality of the heart, whether due to structural, functional, or electrical abnormalities. Heart disease can be categorized as follows:

1. Valvular disease, in which the heart vales don’t open or (more often) close, properly
2. Myocardial disease, in which the heart muscle pumps too weakly or (less often) doesn’t relax adequately
3. Arrhythmias, in which the heart beats too erratically, too fast, or too slow
4. Vascular disease, in which the blood vessels interfere with blood flow
5. Shunts, in which there are abnormal openings between the left and right side of the heart, or between the lungs and the body
6. Abnormally high or low levels of blood
7. Cardiac parasites, such as heartworms; or infections

Heart disease in turn can lead to heart failure. Heart failure manifests in two main ways: low output heart failure, in which the heart can’t pump enough blood to oxygenate the organs; or congestive heart failure, in which fluid leaks from dammed up blood into tissues, causing fluid build-up in the lungs or abdomen.

Signs of low output heart failure include exercise intolerance, weakness, and fainting. Signs of congestive heart failure include coughing, difficulty breathing, or fluid build-up in the abdomen and legs. More advanced cases can also cause a bluish tint to the gums, rhythm abnormalities, and sudden death.

What Are Common Types of Heart Disease?

Heart diseases can be divided in a number of ways, including acquired versus congenital diseases.

Acquired Heart Disease

The majority of heart problems are acquired as a dog ages. These can be divided into conditions affecting the heart valves, and those affecting the heart muscle.

Mitral valve disease is the single most common heart disease, especially in small dogs. In it, the heart’s mitral valve fails to close all the way, allowing blood to escape backwards through the valve opening. When this “regurgitation” is severe, fluid accumulates in the lungs, causing signs of congestive heart failure. Arrhythmias may also develop. Fortunately, only about 30% of dogs with mitral valve disease will progress to heart failure. Treatment is aimed at reducing these signs, rather than eliminating the cause.

Cardiomyopathy, better known as dilated cardiomyopathy (DCM), is the second most common heart disease in dogs, and the most common in certain large breeds. In it the heart muscles are weakened and don’t allow the heart to contract and pump fully. As it worsens, the heart chambers enlarge, the valves may leak, and congestive heart failure develops. Sometimes arrhythmias can cause sudden death. Treatment is aimed at increasing contractility, stabilizing heart rhythm, and reducing signs of congestive heart failure.

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Pericardial effusion occurs when the sac around the heart fills with fluid, making it difficult for the heart to beat. It may occur for no known reason, or in response to inflammation or cancer of the heart. It presents as weakness and difficulty breathing and is usually an emergency. Treatment entails using a syringe to remove the fluid, but often gives only temporary relief.

Heartworm infection is the most common preventable heart condition. Mosquito bites transmit the immature forms, which migrate to the heart and mature, eventually interfering with heart function. Prevention is with monthly medications. Treatment requires prolonged drug therapy.

Congenital Heart Disease

Less than 1% of heart disease in dogs is congenital, meaning the dog is born with the defect. Of these, patent ductus arteriosus and subaortic stenosis make up about half of all cases of congenital heart defects.

Patent ductus arteriosus (PDA), an abnormal opening between two major blood vessels leading from the heart, is the most common congenital heart defect. This opening is normal in fetuses, but normally closes around birth. If it doesn’t close, the blood doesn’t get properly oxygenated, and eventually it can cause congestive heart failure. Treatment is with surgery in small dogs, or with occluding devices placed by catheter in large dogs.

Subaortic Stenosis (SAS) is the second most common congenital heart defect in dogs. It’s characterized by abnormal tissue that obstructs blood flow just below the aortic valve. The heart has to work harder to pump blood past it, eventually causing the heart muscle to thicken and weaken. Treatment is with medications.

Other congenital heart problems include pulmonic stenosis, ventricular septal defect, atrial septal defect, mitral valve dysplasia, tricuspid valve dysplasia, tetralogy of Fallot, cor triatriatum, and persistent right aortic arch.

How Is Heart Disease Diagnosed?

Diagnosing heart disease before the signs are obvious can give you a head start in treatment, and delay progression of the disease. That’s one reason to have your dog checked annually by your veterinarian, or even better, attend a heart health clinic offered at many AKC dog shows.

“The initial symptoms of heart disease can be found with awareness of changes in our pet’s behavior at home and having routine checkups with a primary care veterinarian,” says Bill Tyrrell, DMV, Diplomate, ACVIM (Cardiology), also of Cardiac Care for Pets. “At this checkup, if a heart murmur or irregular heartbeat or rhythm is noted, some diagnostic testing can be performed.” Dr. Tyrrell says that initial testing, like an electrocardiogram (EKG/ECG) or chest radiograph can be helpful. Vets may also do blood testing to look for markers in the blood (NTproBNP or Cardiac Troponin-I) that may help identify heart disease.

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With the progressive understanding over the past few years of the familial nature of many heart diseases, there are certain genetic markers of heart disease than can be evaluated as well (DCM in the Doberman, or ARVC in the Boxer, for example).

Some of the more commonly used diagnostic tools include:

• Auscultation, or listening with a stethoscope, can detect murmurs that indicate valvular disease, and may also indicate a possible arrhythmia. Taking the pulse, usually at the femoral artery, is often used in conjunction with auscultation.
• X-rays can detect an enlarged heart, or if the pericardial sac is filled with fluid
• An electrocardiogram (ECG) records the electrical activity of your dog’s heart to detect heart rhythm problems. This is done with your dog awake, and the results can be sent remotely for reading by a specialist.
• A Holter monitor is basically a portable ECG that your dog wears for 24 hours at home, allowing a longer period to detect rhythm problems and correlate them with your dog’s activity.
• A cardiologist can perform an echocardiogram, which uses ultrasound to visualize the heart valves, how much the heart contracts, thickness of the heart walls, and regurgitation at the valves
• Blood and urine tests can detect heartworms, heart disease markers, or the condition of other organs that may affect, or be affected by, the heart.
• Blood pressure can be measured, but is more difficult to take in dogs compared to humans.

How Is Heart Disease Treated?

Most treatments are aimed at controlling signs, rather than curing the condition. Limited exercise is generally suggested for most conditions. The goal is to prevent the heart from becoming overburdened.

Low-sodium cardiac diets are important to prevent fluid build-up in congestive heart failure. The extent of sodium restriction depends on the severity of the condition. A cardiologist is in the best position to advise you about diet.

Surgical intervention has generally been limited to implantation of pacemakers for dogs with irregular or slow heart rates, and surgery or balloon therapies for PDA. That’s changing though.

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“Open-heart surgery for the first time has become available consistently in the United States this past year to repair the mitral valve in dogs at the veterinary college of the University of Florida,” says Rosenthal, “A novel catheter procedure (TEER- transcatheter edge to edge repair) is being offered at some institutions around the US to help treat the most common degenerative valve disorder in dogs.”

Some commonly used heart medications are:

• Furosemide, which helps congestive heart failure by removing excess fluid, especially from the lungs. It makes your dog urinate more, but also increases thirst.
• Enalapril and benazepril are angiotensin-converting enzyme (ACE) inhibitors that reduce blood pressure and increase the heart’s output
• Sotalol or mexiletine help stabilize arrhythmias
• Pimobendan, sold under the brand name Vetmedin, helps heart muscles contract. It’s often prescribed for DCM.
• Spironolactone is a mild diuretic that seems to increase life spans in dogs with mitral valve disease
• Digoxin may be used for short term improvement of heart function
• Vetoquinol is a new drug for dogs used alongside other cardiac drugs to help decrease fluid build-up in the lungs from congestive heart failure
• Supplements with ingredients such as taurine and L-carnitine may improve heart function

This is far from a complete list, and new drugs are being introduced all the time. Drugs should be given under the guidance of a veterinary cardiologist, as some can be counterproductive if given before they’re really needed, and others can negatively impact quality of life.

Prevention and early detection and treatment is the best weapon. “Preventative care includes the use of heartworm preventative therapy, and keeping your dog physically fit and on a well-balanced diet,” according to Tyrrell. “Certain nutritional deficiencies and some types of diets have been associated with the development of heart disease, so working with your family veterinarian to choose a well-balanced diet for your pet is imperative. If you have a breed at risk for heart disease (Doberman Pinschers, Cavalier King Charles Spaniels, and many other breeds) checking for genetic mutations and vigilant monitoring for heart disease is recommended, too.”

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