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    Heart Disease in Senior Dogs

    There’s no single cause of heart disease in dogs. As dogs age, their risk of heart conditions increases. No matter your dog's heart condition, it’s important to spot the signs early. Dr. Geri Lake-Bakaar recently joined us for a webinar to discuss the diagnostic tools available to assess cardiac disease, approaches to managing it, and the long-term prognosis.

    Types of Heart Disease

    The most common form of heart disease seen in dogs is mitral valve disease. The mitral valve is the valve that runs between the right and left ventricles in the heart. Its primary function is to keep blood from flowing backward through the heart chambers. The disease occurs when the mitral valve thickens and becomes “floppy.” Sometimes, this results in the “regurgitation” of blood backward into the former chamber.

    There are many different types of heart disease caused by other issues within the heart muscle. Dr. Lake-Bakaar typically sees mitral valve disease in smaller breeds like Chihuahuas, Boston terriers, and, most often, the Cavalier King Charles spaniel.

    Another form of heart disease is dilated cardiomyopathy, in which the left chamber of the heart becomes enlarged, stretching the muscular wall and making it thinner and weaker. This type of heart disease is often seen in larger breeds such as boxers, Irish wolfhounds, Great Danes, and, famously, Dobermans.

    A third and increasingly more common form of heart disease is dietary-associated cardiomyopathy, which can occur in dogs of any size, breed, or age. It has been linked to the use of lentils, peas, chickpeas, and other legumes that became popular in dog food over the past decade, first introduced as alternatives to grain.

    According to Dr. Lake-Bakaar, about 40-50% of dogs will end up on medication due to heart disease. However, only 10% of dogs develop severe heart disease or congestive heart failure. This is partly because heart disease is relatively slow in progression but also due to advances in veterinary care that have helped doctors catch the disease much earlier than they used to.

    Signs of Heart Disease

    Typically, the first indication of heart disease in dogs is a murmur that your vet hears at a routine visit. Heart murmurs can be identified by listening to your dog’s chest with a stethoscope. If a murmur is detected, your vet will grade it based on intensity:

    • Grade I: Very Soft - These are the least serious. They are extremely soft in sound, barely audible.
    • Grade II: Focal - A soft sound heard through the stethoscope.
    • Grade III: Easy To Hear - Intermediate loudness radiating to multiple locations.
    • Grade IV: Loud - Moderate to intense and can be heard on each side of the chest.
    • Grade V: Loud and can be heard even when the stethoscope barely touches the chest. They can also be felt by holding a hand against the chest.
    • Grade VI: Very loud and can be felt by touching the chest.

    Dr. Lake-Bakaar noted that the intensity of the murmur does not necessarily indicate less or more advanced disease. The more important metric, she says, is how quickly a patient progresses from one level of intensity to the next. It is also important to remember that the scale is subjective to the veterinarian.

    Additional signs may be observed as the disease progresses. These include:

    • A dry cough that has persisted for weeks to months, usually worse when the dog is lying down or sleeping
    • Increased respiratory rate or effort
    • Exercise intolerance or collapsing with exertion

    Most dogs will not show outward symptoms before the disease is diagnosed via heart murmur.


    Diagnostic Tools

    Once a heart murmur is detected and the disease is suspected, your vet may recommend one or more additional tests to monitor your pet or gain further insight into the stage of your pet’s disease.

    Sleeping Respiratory Rate Monitoring
    This is an excellent way for pet owners to help monitor their dog’s disease progression at home. Perform this test once a week when your dog is sleeping:

    • Count the times your dog’s chest goes up and down (one breath) over 15 seconds.
    • Multiply that number by 4 to get their “breaths per minute.” 
    • A bpm < 30 is considered normal and requires no further action.
    • A bpm of 40-50 is considered slightly abnormal, and you should plan to see your vet within a day or two.
    • A bpm > 50, especially if accompanied by collapsing or coughing, is considered severely abnormal, and you should take your dog to an emergency vet.

    Chest X-Rays
    Imaging the chest cavity is one of the first diagnostic tools a veterinarian may use after hearing a heart murmur. X-rays can show the heart's shadow, size, blood vessels, and the presence or absence of fluid in the lungs (which can be evidence of heart failure). When viewing an X-ray, fluid will appear white, while air will appear black. The difficulty in using only X-rays in diagnosing heart disease is that white space could also indicate infection or inflammation. Also, they are a snapshot in time rather than a moving picture. So, Dr. Lake-Bakaar usually recommends further testing to confirm.

    Blood Work
    A BNP test is an in-house blood test your vet can perform to help assess the likelihood of cardiac-related diseases. Its primary function is to measure cardiac stretch, or how well the heart is handling the disease and whether it is straining.

    • < 1000 is considered typical and unremarkable
    • 1000-2000 would warrant further echocardiography testing
    • > 2000 is of concern

    Echocardiography
    Echocardiography can help fill in the picture where X-rays left off. A cardiologist must perform these tests, but they allow the doctor to see all heart chambers, track changes in pressure, and look for fluid. It also lets them see the heart functioning in real-time. It is important to note, however, that echocardiography alone cannot determine the presence or absence of congestive heart failure as an end-stage disease.

    Electrocardiography
    This test is typically used as a pre-anesthetic screening in older patients or those suspected of having heart disease. An electrocardiogram assesses heart rhythm and the electrical function of the heart. It can provide insight into an irregular heartbeat. It is also available as a 24-hour halter monitor that measures your dog's EKG. Pain, stomach illness, or lung disease can also cause irregular heart rhythms, especially in older dogs, so EKGs will usually be used with many other tests to confirm heart disease.


    Treatment Options

    Treatment for heart disease can be separated into two stages: inpatient and outpatient.
    Outpatient care is for dogs experiencing mild or moderate disease. They may have mild symptoms or no symptoms at all. An outpatient-stage dog will typically be placed on preventative medication like Vetmedin (generic form: Pimobendan). This drug helps improve heart function, prolongs the onset of heart failure, and can even reduce heart size in about a month.

    Additionally, some pets may benefit from an RAAS Inhibitor like Benazepril/Enalapril or Spironolactone. RAAS stands for renin-angiotensin-aldosterone system. This body system is primarily responsible for keeping us alive during a life-or-death event by regulating blood volume, electrolyte balance, and vascular resistance. Although it is a beneficial function when truly needed, it can be improperly activated by heart disease, resulting in overall patient health decline. RAAS inhibitors help to mitigate that stress response.

    Inpatient care is typically reserved for dogs who are showing significant signs of heart failure. This type of care benefits pets requiring more advanced monitoring by a care team. This can include oxygen support, IV medications, and quick access to follow-up testing. Additionally, most animal hospitals will have Snyder Oxygen Kennels available. These specialized kennels allow vets to change temperature and humidity, monitor oxygen and carbon dioxide levels, and administer treatments case-by-case.

    Living with Heart Disease

    General Anesthesia: Most pet parents have concerns regarding the use of general anesthesia in senior dogs, especially for those with heart disease. Dr. Lake-Bakaar notes that most veterinarians will look for fluid overload of the heart, any dysfunction, or arrhythmia in older patients. These are also the symptoms she would be paying close attention to for any patient suffering from heart disease. The risk is very low in mild cases, with the primary monitoring focus on not overloading the heart with fluids. For moderate cases, the standard is closer monitoring, possibly with a dedicated anesthesiologist on site. In severe disease or dogs actively in congestive heart failure, most vets will avoid elective surgeries. Dr. Lake-Bakaar says that it isn’t so much a concern that the pet will die “on the table” but rather that the recovery period following surgery could push a dog with severe disease into heart failure.


    Exercise: Dr. Lake-Bakaar says that the level of exercise suitable for your dog depends on the severity of the disease. Many dogs will try to keep up with their owners, regardless of how they are feeling, and they may not always show that they are uncomfortable. Normal activity is acceptable for most dogs with mild to moderate disease. She recommends avoiding strenuous activity for dogs with known severe disease. Longer, slower walks are usually best, increasing the length of the walk but decreasing the intensity.


    Diet: Diet can play an important role in mitigating some of the body’s stress responses for dogs suffering from heart disease. Congestive heart failure is known to cause retention of salt, chloride, and water, making the salt content of your dog’s food a significant factor to consider. Typically, a diet high in protein and omega-3 fatty acids but low in sodium is the best option for a dog with heart disease. Dr. Lake-Bakaar recommends Royal Canid Early Cardiac and Hills H/F. It is important to discuss dietary recommendations with your veterinarian, as other ailments like kidney disease or urinary issues could change the ideal diet for your pup.

    Prognosis

    The good news is that most dogs manage heart disease quite well. For mild and moderate cases, when diagnosed in older dogs, heart disease doesn’t tend to be life-limiting. For patients who have congestive heart failure, the prognosis is 1.5-2.5 years following the first onset of CHF symptoms.

    About the Presenter

    Dr. Geri Lake-Bakaar graduated from Harvard University in 2003 (BA), Cornell University in 2007, and the University of California, Davis (DACVIM, Cardiology) in 2013. Between veterinary school and her residency, she completed a rotating internship at the Animal Medical Center and a post-doctorate fellowship at Harvard/MGH. She is devoted to caring for all animals and providing compassionate, quality care to her patients. Geri is interested in education and provides continuing education lectures to veterinarians. She has also designed a series of client education materials. She is a section editor for an educational website on the Veterinary Information Network. Geri loves running races and riding her Peloton in her free time. Geri and partner Michael have two dogs (Max and Sir Fur), a horse (Brad), and a sassy 6-year-old daughter who also loves animals.