Enlarged Heart in Dogs: Medications and Treatment Options

Name: Enlarged Heart in Dogs: Medications and Treatment Options
Creator: Dr. Zubair Khalid

By Dr. Zubair Khalid, DVM, MS, PhD · 2026-10-02

An enlarged heart in dogs is almost always managed with medication, not cured with it. The core of that treatment is a drug called pimobendan, often combined with a diuretic and an ACE inhibitor, and each one does a different job. This article explains what enlarged heart in dogs medication actually looks like, how each drug works, and why so-called natural treatments cannot replace it.

This article is educational and is not a substitute for veterinary diagnosis or treatment.

Quick Answer

Pimobendan is the drug most often prescribed when a dog's heart is enlarged, and it is used both before and after congestive heart failure begins [1].
Most dogs with an enlarged heart and fluid buildup take more than one medication, commonly pimobendan, a diuretic such as furosemide, and an ACE inhibitor such as enalapril [2].
These drugs control signs and extend good-quality time. They do not reverse the underlying valve or muscle disease.
Doses are calculated by your veterinarian from your dog's weight, kidney values, and stage of disease. Never adjust a dose on your own [3].
No herbal, grain-free, or supplement protocol has been shown to replace heart medication for an enlarged heart. Giving one instead of prescribed drugs can cost your dog time.

What Enlarged Heart in Dogs Medication Is and What It Is Used For

An enlarged heart is not one disease. It is a physical change that happens when the heart works against a leaky valve, a weak muscle, or high pressure. The most common cause in small dogs is myxomatous mitral valve disease, where the mitral valve thickens and leaks, and the left side of the heart enlarges over time [4]. In larger breeds, dilated cardiomyopathy is a frequent cause, with a stretched, poorly contracting ventricle [5].

Your veterinarian treats the disease causing the enlargement, not the enlargement by itself [3]. That is why two dogs with the same heart size can be on different drug plans.

The medications used for an enlarged heart fall into a few groups:

Inodilators (pimobendan). These make the heart pump harder and open up blood vessels. Pimobendan is the standard example in dogs [5].
Diuretics (furosemide and similar drugs). These pull excess fluid out of the lungs and body so your dog can breathe [6].
ACE inhibitors (enalapril and similar drugs). These lower the workload on the heart and are part of standard therapy for congestive heart failure [2].
Other drugs as needed. Depending on rhythm problems or blood pressure, your veterinarian may add medications for rate, rhythm, or pressure control [3].

If your dog has fluid in the lungs from a failing heart, that is congestive heart failure, and it changes the urgency of treatment. You can read more about how that stage is managed in Canine Congestive Heart Failure: Staging and Therapeutic Plan.

How Pimobendan Works in Dogs With an Enlarged Heart

Pimobendan is the medication most owners ask about, often by brand name. It works in two ways at once. It makes the heart muscle contract more forcefully, and it relaxes blood vessels so the heart does not have to push against as much resistance [5].

In a study of healthy awake dogs, a single dose of pimobendan increased left ventricular systolic performance, with measurable changes in how the heart muscle deforms during each beat [7]. In a dog hospitalized with decompensated dilated cardiomyopathy, intravenous pimobendan produced a rapid but temporary improvement in systolic function, and the dog was later switched to the oral form [5]. That pattern is why injectable pimobendan is sometimes used in a crisis and oral pimobendan is used for long-term care.

Pimobendan is also used before heart failure starts. In dogs with mitral valve disease and an enlarged heart, giving pimobendan during this preclinical phase reduces heart size and lowers the risk of developing congestive heart failure [1]. This is one of the clearest reasons to keep routine cardiology rechecks. If your dog has a murmur and an enlarging heart but no symptoms yet, medication may already be on the table.

One finding owners should understand: in a study of dogs that were already on pimobendan before heart failure began, survival time after heart failure started was shorter than in dogs that had not received it earlier [1]. This does not mean the drug is harmful. It most likely means the dogs treated early had more advanced disease by the time failure arrived. Your cardiologist weighs this kind of information when planning treatment.

How Diuretics and Other Heart Medicines Work

Furosemide is the diuretic most often used when a dog's heart is enlarged and fluid is building up. It acts on the kidneys to increase sodium and water loss, which reduces the fluid load on the heart and lungs [6]. In a study of dogs with acute left-sided congestive heart failure, higher urinary sodium levels after an intravenous furosemide dose were linked to better decongestion and shorter hospital stays [6]. In plain terms, the drug works best when the kidneys respond to it, which is one reason your veterinarian checks bloodwork.

Enalapril and other ACE inhibitors are part of standard therapy for dogs in heart failure. In one study, dogs with stage C and D heart failure received pimobendan, enalapril, and furosemide together for four weeks, and researchers tracked changes in kidney and liver blood flow during that period [2]. This combination is common because each drug addresses a different part of the problem.

Some dogs need additional drugs. The goals of heart treatment include controlling fluid buildup, improving circulation, regulating heart rate and rhythm, keeping enough oxygen in the blood, and lowering the risk of blood clots [3]. Your veterinarian picks from a range of medications based on which of those goals your dog is missing [3].

If your dog also has high blood pressure, that changes the plan too. See Canine Systemic Hypertension: Diagnosis and Management.

Dosing Basics for Dog Medicine for an Enlarged Heart

Your veterinarian decides the dose. Doses are based on your dog's weight, kidney and liver values, the stage of heart disease, and what other drugs are on board. Do not copy a dose from another dog or from an online forum.

Give the medication exactly as prescribed. The veterinary guidance on heart drugs is direct: medications must be given exactly as prescribed, or they may not work and may even cause serious harm [3].

A few practical points:

Pimobendan is usually given about an hour before food, on an empty stomach, because absorption is better that way. Your veterinarian will confirm the schedule for your dog.
Furosemide is often given once or twice daily. Timing matters because it makes your dog urinate more for several hours after each dose.
ACE inhibitors are typically given once or twice daily and can be given with or without food.

If you miss a dose, do not double up. Give the next dose at the normal time and call your veterinarian if you are unsure. If your dog vomits a dose or refuses food, that is worth a phone call the same day, especially if your dog is on a diuretic.

Never stop heart medication suddenly on your own. Some dogs become stable enough that a veterinarian may reduce or stop a diuretic, but that decision comes from recheck exams and imaging, not from how your dog looks at home. In one report, a small number of dogs with mitral valve disease and heart failure stayed stable for at least a year after loop diuretics were withdrawn, but this involved only six dogs out of more than 3,000 records reviewed [4]. That is a rare outcome managed by veterinarians, not a do-it-yourself plan.

Side Effects of Dog Medicine for Enlarged Heart

Side effect	How common or serious	What to do
Loss of appetite, vomiting, loose stool	Common with pimobendan and other heart drugs, usually mild	Call your veterinarian. A dose timing change or a small meal before the pill may help
Increased thirst and urination	Expected with furosemide	Keep fresh water available. Report extreme drinking or urination
Lethargy or weakness	Can signal dehydration or electrolyte problems from diuretics	Call your veterinarian the same day
Fainting or collapse	Serious, may mean rhythm problems or low blood pressure	Treat as an emergency
Fast or labored breathing at rest	Serious, often means fluid is returning	Emergency visit now
Increased kidney values on bloodwork	Possible with diuretics and ACE inhibitors	Your veterinarian monitors this with routine lab work [2]
Blood clotting problems	A concern in some heart diseases, which is why clot prevention is a treatment goal [3]	Follow your veterinarian's monitoring plan

Many side effects are manageable with a dose adjustment. The danger is when an owner stops the drug instead of calling. That can let fluid build back up in the lungs within days.

Who Should Not Take These Drugs and What Interacts With Them

Pimobendan is not right for every dog. It is used for heart failure linked to poor pumping function, such as dilated cardiomyopathy, and for enlarged hearts from mitral valve disease [1][5]. Dogs with certain outflow obstructions or severe rhythm problems may need a different plan. Your veterinarian makes that call after an echocardiogram.

Diuretics need extra caution in dogs with kidney disease or dehydration, because they remove fluid and electrolytes. ACE inhibitors also affect the kidneys and potassium levels, which is why bloodwork is repeated after starting or changing a dose [2].

Tell your veterinarian about everything your dog takes, including:

Other heart drugs, since combinations are common and doses must be balanced [2]
NSAIDs and steroids, which can affect fluid balance and blood pressure
Any supplement, herbal product, or "heart support" powder, even if it seems harmless
Any prescription food, especially low-sodium diets, which are sometimes recommended in heart failure [3]

Do not add a new supplement without asking. Some interact with diuretics or blood pressure, and none replace proven heart medication.

Overdose and When to Call for Help

Signs of overdose can include severe vomiting, diarrhea, weakness, collapse, or fainting. These can happen with too much diuretic, too much blood pressure medication, or a double dose of pimobendan.

If you think your dog received too much medication, call your veterinarian or an emergency clinic right away. You can also call poison control. The ASPCA Animal Poison Control Center is available at (888) 426-4435, and the Pet Poison Helpline is available at (855) 764-7661. Both may charge a consultation fee.

Bring the medication bottle with you. Knowing the drug name, strength, and how many pills were taken helps the veterinarian act fast.

Enlarged Heart in Dogs Natural Treatment: What It Can and Cannot Do

Owners often search for an enlarged heart in dogs natural treatment because the diagnosis feels frightening and the drugs feel heavy. It is fair to ask questions. It is not safe to swap proven medication for supplements.

Here is the honest position. Heart disease in dogs generally does not go away. It almost always becomes more serious over time and can lead to death [8]. The drugs used for an enlarged heart are the ones that have been shown to reduce heart size, delay heart failure, and extend survival [1]. No supplement has that evidence.

What "natural" support can realistically mean:

Diet. A low-sodium diet may be recommended in congestive heart failure to help the body shed excess fluid [3]. This is a real, veterinarian-directed step, not a substitute for drugs.
Weight and activity. Keeping your dog lean and using gentle, consistent exercise helps the heart's workload. Your veterinarian sets the activity level.
Monitoring at home. Counting your dog's resting breathing rate each day is one of the most useful things you can do. A rising rate often means fluid is returning before you see other signs.
Coexisting conditions. If your older dog has other diseases, they affect the heart plan. For example, see Dog Hyperthyroidism: Symptoms, Diagnosis, and Treatment Options.

What natural treatment cannot do is replace pimobendan, furosemide, or an ACE inhibitor in a dog with an enlarged heart and fluid buildup. If cost is the barrier, say so out loud at your appointment. Veterinarians can often adjust the plan, prioritize the most important drug, or point you to options. Skipping medication quietly is the worst outcome.

Limitations and When to Contact a Veterinarian

Heart medication controls disease. It does not cure it, and it does not work the same way in every dog. Your dog's individual case needs a veterinarian who can examine, image, and monitor the heart over time.

Call your veterinarian the same day if you see:

Your dog refuses food or vomits after a dose
Increased thirst or urination that seems extreme
Weakness, wobbling, or unusual tiredness
A resting breathing rate that is higher than your dog's normal baseline

Go to an emergency clinic now if you see:

Labored breathing, especially with the elbows out and belly moving hard
Blue or gray gums
Collapse or fainting
A resting breathing rate that stays high and keeps climbing
A swollen belly that appeared quickly

Keep routine rechecks even when your dog looks great. Heart size, kidney values, and drug doses are checked at these visits, and small changes are easier to handle early [2].

Frequently Asked Questions

What is the most common medication for an enlarged heart in dogs?

Pimobendan is the medication most often used for an enlarged heart in dogs. It improves how strongly the heart pumps and lowers the resistance the heart pumps against [5]. Many dogs also take a diuretic and an ACE inhibitor alongside it [2].

Can I give my dog natural remedies instead of heart medication?

No. Natural remedies have not been shown to reduce heart size or delay heart failure the way pimobendan has [1]. A low-sodium diet can help with fluid, but it is used with medication, not in place of it [3]. Always tell your veterinarian about any supplement before giving it.

How long can a dog live with an enlarged heart on medication?

It varies widely by disease, stage, and how early treatment started. In one study, median survival after heart failure began ranged from about six months to about a year depending on whether pimobendan was started before failure [1]. Your veterinarian can give you a realistic range for your dog.

What happens if I miss a dose of my dog's heart medicine?

Give the next dose at the regular time and do not double up. Call your veterinarian if you are unsure or if your dog seems unwell. Missing doses repeatedly can let fluid build back up, and the guidance is clear that heart medications must be given exactly as prescribed [3].

Does an enlarged heart in dogs ever get better?

The enlargement itself usually does not reverse, but it can shrink somewhat with treatment. Pimobendan given in the preclinical phase of mitral valve disease reduces cardiac dimensions and lowers the risk of heart failure [1]. The underlying valve or muscle disease still needs lifelong management.

References

Survival of dogs with myxomatous mitral valve disease administered preclinical pimobendan in comparison to pimobendan-naïve dogs from the onset of congestive heart failure. Journal of veterinary cardiology : the official journal of the European Society of Veterinary Cardiology, 2026.
Changes in hepatic and renal Doppler ultrasonography: Current standard therapy in dogs with congestive heart failure. Open veterinary journal, 2025.
Treatment of Cardiovascular Disease in Dogs - Dog Owners. Merck Veterinary Manual.
Rare stability in dogs with myxomatous mitral valve disease: Clinical observations of loop diuretic withdrawal after congestive heart failure. Open veterinary journal, 2026.
Acute hemodynamic and echocardiographic responses to pimobendan versus levosimendan in a dog with decompensated dilated cardiomyopathy. Veterinary research communications, 2026.
Spot urinary electrolytes are associated with decongestion and duration of hospitalization in dogs with acute left-sided congestive heart failure secondary to myxomatous mitral valve disease. American journal of veterinary research, 2026.
Characterization of global and regional left heart function using advanced echocardiography following intravenous administration of pimobendan in awake dogs. Frontiers in veterinary science, 2026.
Heart Disease in Dogs - Dog Owners. Merck Veterinary Manual.