What Dog Owners Need to Know About Canine Heart Disease
Heart disease in dogs is most often an acquired, age-related condition affecting either the heart valves or heart muscle (cardiomyopathy). Early detection usually happens during routine vet visits when a murmur or arrhythmia is heard, not from symptoms at home. By the time owners notice respiratory signs like coughing or exercise intolerance, heart disease is often advanced, which is why annual vet exams with a stethoscope are critical for catching problems early.
In this episode, board-certified veterinary cardiologist Dr. Jake Jacobson breaks down the most common forms of heart disease affecting dogs in the Charleston Lowcountry and beyond. Unlike what many dog owners assume, the vast majority of canine heart disease is not congenital (present from birth) but acquired over time as dogs age. The two primary categories are valvular disease, where heart valves wear down and begin to leak, and cardiomyopathy (heart muscle disease), where normal heart muscle is replaced by scar tissue or fat that cannot pump or relax properly.
Dr. Jacobson explains that dilated cardiomyopathy (DCM) became widely discussed roughly a decade ago when a spike in cases was linked to grain-free and legume-heavy dog foods. Dogs on diets high in peas and lentils were found to have difficulty absorbing essential amino acids, leading to weakened heart muscle. In many cases, switching the dog off that diet and onto a more balanced food reversed the condition within six to eighteen months. Genetic DCM, however, is not reversible and is most common in large breeds like Doberman Pinschers.
Heartworm disease, while preventable, remains a concern in the South. Dr. Jacobson describes severe infestations where worms living in the pulmonary arteries cross into the heart and can even be physically extracted through the jugular vein in emergency cases (a procedure called caval syndrome). Monthly preventatives remain the most effective defense.
Most heart disease is detected not by the owner noticing symptoms, but by a veterinarian hearing a murmur or arrhythmia during a routine exam or picking up abnormal bloodwork. By the time a dog shows clear signs like coughing, labored breathing, or fainting, the disease is typically in an advanced stage. Dr. Jacobson emphasizes the value of annual vet visits and early referral to a cardiologist when something abnormal is detected, as early intervention with medication can delay or prevent heart failure.
For dogs diagnosed with heart disease, Dr. Jacobson recommends a low-sodium diet, fish oil (omega-3s), lean unseasoned protein (chicken, beef, turkey, eggs, fish), and a cardiac-support multivitamin. Dogs should be allowed to self-limit their exercise rather than being forced into strict rest, and maintaining a healthy body weight with good muscle mass is critical, as cardiac cachexia (muscle wasting) can occur in advanced cases.
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Frequently Asked Questions
What are the early signs of heart disease in dogs?
Most early-stage heart disease in dogs has no visible symptoms at home. It is usually detected by a veterinarian during a routine exam when they hear a heart murmur (an abnormal heart sound) or an arrhythmia (irregular heartbeat) with a stethoscope, or when bloodwork flags a cardiac marker. By the time owners notice symptoms like coughing, labored breathing, exercise intolerance, or fainting, the disease is often advanced. This is why annual vet visits are so important for early detection.
What causes dilated cardiomyopathy (DCM) in dogs?
Dilated cardiomyopathy (DCM) can be genetic or diet-related. Genetic DCM is most common in large breeds like Doberman Pinschers and occurs when the heart muscle is replaced by scar or fatty tissue that cannot pump effectively. Diet-associated DCM became more common about ten years ago with the rise of grain-free and legume-heavy dog foods. High concentrations of peas and lentils in some diets appear to prevent dogs from absorbing essential amino acids needed to build heart muscle. In many diet-related cases, switching to a more balanced food and giving the heart time to recover can reverse the condition within six to eighteen months.
How is heartworm disease treated in dogs?
Heartworm disease is treated with a series of injections (typically three) that kill the adult worms living in the pulmonary arteries. The protocol is staggered to allow immature worms time to mature so they can be killed in a second round. In severe infestations where worms have crossed into the heart and jugular vein (caval syndrome), they can be physically extracted through the jugular using forceps or a specialized catheter before injections are given, as killing a massive worm burden all at once could block the arteries and be fatal. Monthly heartworm preventatives remain the most effective way to avoid infection entirely.
What should I feed a dog with heart disease?
Dogs with heart disease benefit from a low-sodium diet, as sodium increases thirst and water retention, which a compromised heart struggles to handle. Add fish oil (omega-3 fatty acids) for anti-inflammatory and antioxidant support. Lean, unseasoned protein sources like chicken, ground beef, turkey, eggs, and fish provide the amino acids the heart muscle needs as fuel. A cardiac-support multivitamin can help ensure the dog is not depleting micronutrients faster than they are being replaced. Prescription cardiac diets from major veterinary brands hit these marks and are a convenient option, but any high-quality food meeting these criteria works.
Can a dog with heart disease still exercise?
Yes, in most cases. Dogs with heart disease should be allowed to self-limit their activity rather than being placed on strict rest. Let the dog decide when to stop or slow down. Some dogs with severe arrhythmias or advanced disease may faint with excitement or exertion and need closer monitoring, but for the majority of cardiac patients, continuing normal activity is healthy and recommended. Low-intensity, steady exercise (like walking) is ideal, with occasional higher-intensity play if the dog tolerates it well.
Which dog breeds are most prone to heart disease?
Small breeds are prone to age-related mitral valve disease. Large and giant breeds, particularly Doberman Pinschers, Great Danes, Boxers, and Irish Wolfhounds, are at higher risk for dilated cardiomyopathy (DCM). Cavalier King Charles Spaniels are genetically predisposed to early-onset mitral valve disease. Any breed can develop diet-associated DCM if fed a diet that blocks absorption of essential amino acids, but this is most commonly seen in dogs on grain-free, legume-heavy foods.
What tests does a veterinary cardiologist perform?
A veterinary cardiologist typically performs an echocardiogram (ultrasound of the heart) to visualize the heart’s structure, size, function, and valve movement in real time. An electrocardiogram (ECG or EKG) assesses the heart’s electrical activity, including rate and rhythm, and can detect arrhythmias or conduction problems. Chest X-rays look for fluid in the lungs (pulmonary edema), a sign of heart failure. Blood pressure is also measured. In some cases, a Holter monitor is used to record the heart’s electrical activity over 24 to 48 hours to assess arrhythmia burden throughout the day and night.
Can diet-related heart disease in dogs be reversed?
Yes, in many cases. If a dog develops dilated cardiomyopathy (DCM) due to a diet that prevents absorption of essential amino acids, switching to a better-quality food and giving the heart six to eighteen months to recover can reverse the condition. The dog is still treated with cardiac medications during this period, but over time, if the heart begins to look and function better on follow-up echocardiograms, the diagnosis is confirmed as diet-related and the medications can eventually be tapered or stopped. If no improvement is seen, the DCM is more likely genetic.
