Dog Heart Disease Symptoms: Early Signs and When to Worry

Early Signs of Heart Disease in Dogs

• A new heart murmur found at a checkup^1,2
• Tiring sooner on walks or not wanting to play as long^5,15
• A slow rise in sleeping breathing rate, even if it's still under 30^4,11
• Restlessness at night, or a new soft cough^3,10

Regular checkups matter, especially for at-risk breeds such as Cavaliers, small older dogs and Dobermans. See heart disease in dogs.

Main Symptoms of Heart Disease and Heart Failure

• Fast or labored breathing while resting or asleep, from fluid in the lungs^3,7
• Coughing, often at night or when lying down; a worsening cough in a dog on heart medicine can mean worsening heart failure^10,4
• Exercise intolerance: lagging, sitting down on walks, or refusing to walk^15,5
• Fainting (syncope), often caused by an abnormal heart rhythm^8,9
• Swollen belly from fluid (ascites), mainly in right-sided heart failure^1,4
• Pale or bluish gums, weakness and collapse^4,7
• Poor appetite, weight loss and muscle wasting¹⁶

Sadly, some dogs with heart disease die suddenly without obvious warning signs.⁴ See congestive heart failure in dogs.

Heart Cough or Something Else?

The same small, older dogs that get mitral valve disease often have airway problems too, so a murmur in a coughing dog doesn't automatically mean the heart is to blame.² Your vet will usually take chest X-rays to tell them apart.^2,17

• Heart failure cough: usually comes with faster breathing at rest and often at night. Fast breathing is a more reliable sign of heart failure than coughing.^10,11,13
• Collapsing trachea: a dry, harsh "goose honk" cough in toy and small breeds, often triggered by excitement, pulling on the collar, eating or drinking. Heart disease and a collapsing trachea can occur together.^6,18
• Chronic bronchitis: a cough that lasts at least 2 months, mostly in middle-aged and older small dogs, often triggered by excitement, activity, smoke or other irritants.^19,17
• Kennel cough and other infections: a harsh cough, often a few days after contact with other dogs; it usually clears in 1 to 3 weeks.¹⁹

See why dogs cough.

Fainting vs. Seizures

• Fainting (syncope): often triggered by exercise, excitement or coughing. The dog goes limp and usually recovers within seconds to a couple of minutes.^8,9,14
• Seizure: often starts at rest or during sleep, usually lasts 1 to 2 minutes or longer, may include paddling, jaw chomping or drooling, and is followed by confusion that can last much longer.^14,8

Video an episode if you safely can, since it helps your vet tell them apart. A 24-hour heart monitor (Holter) is a common next test for fainting.⁸ Fainting caused by heart disease carries a higher risk than other causes, so it always needs a vet visit.⁹ See seizures in dogs.

Home Checks for Heart Disease

1. Count the sleeping breathing rate: when your dog is asleep and not dreaming or panting, count chest rises for 30 seconds and double it. Most healthy dogs breathe under 30 times a minute while asleep.^12,7 Write it down several times over a week to learn your dog's normal, and report a clear rise even if it's still under 30.⁴
2. Check gum color: healthy gums are pink. Pale, gray or blue gums need a vet right away.^7,4
3. Watch exercise: note if your dog tires sooner, breathes hard or sits down on walks.¹⁵
4. Track the belly and weight: a growing waist with weight loss elsewhere can mean fluid buildup.¹

Some vets use 35 breaths a minute as the cutoff for calling.^7,5 Research in healthy dogs and dogs with heart disease supports 30 as a reasonable early-warning level.^12,20,11

When Heart Symptoms Are an Emergency

Difficulty breathing is an emergency, and breathing trouble that doesn't settle with rest almost always needs immediate veterinary care.⁷ Go now for labored breathing, blue or gray gums, collapse, repeated fainting, or a severe cough with breathing difficulty.^7,10,8

Frequently Asked Questions

What are the first signs of heart disease in dogs?

Often none: a murmur at a checkup is the first clue. Early signs include tiring sooner, a slow rise in sleeping breathing rate, restlessness at night and a new cough.

What does a heart cough in a dog sound like?

Often a soft, persistent cough, worse at night or when lying down, usually with faster breathing. A harsh "goose honk" is more typical of a collapsing trachea.

What can be mistaken for heart failure in dogs?

Collapsing trachea, chronic bronchitis, pneumonia, lung tumors and laryngeal paralysis can all cause coughing or breathing trouble. Chest X-rays help tell them apart.

Is it normal for a dog with heart failure to breathe fast?

Fast breathing at rest is a key sign that heart failure is uncontrolled. A sleeping rate consistently over 30 a minute means call your vet; labored breathing means go now.

What is a normal breathing rate for a sleeping dog?

Usually under 30 breaths a minute, and often 10 to 20. Track your own dog's normal and report a clear rise.

Can heart disease cause fainting in dogs?

Yes. Abnormal heart rhythms and advanced heart disease are common causes of fainting, especially during exercise or excitement. Any fainting episode needs a vet visit.

At what age do dogs get heart disease?

Mitral valve disease usually appears in middle age or later, often earlier in Cavaliers. DCM often shows up in middle-aged large breeds, and congenital defects are present from birth.

Can a dog have heart disease without symptoms?

Yes. Many dogs have a murmur or an enlarged heart for months or years before symptoms. Some are started on pimobendan at this stage to delay heart failure.