Heart disease affects approximately 10 to 15% of dogs, with much higher prevalence in certain breeds. Often first detected as a murmur on routine exam, these conditions can be managed for years with appropriate treatment.
Definition
What is canine heart disease?
Canine heart diseases divide into congenital (present at birth, 5 to 8% of cases) and acquired (developing over time, 92 to 95% of cases). In small breeds, degenerative mitral valve disease (MVD) dominates; in large breeds, dilated cardiomyopathy (DCM) is most common.
~75%
of canine cardiac diseases are valvular
100%
of CKCS over 10 years old have a heart murmur
+15 months
extended survival with pimobendan at Stage B2 (EPIC trial)
Cardiologist
recommended from Stage B2 for optimal treatment planning
~75% of cardiac disease
Small and medium breeds
Mitral Valve Disease (MVD)
Progressive degeneration of the mitral valve leaflets, which eventually leak. The heart compensates by hypertrophying, then develops congestive heart failure (CHF).
Progressive weakening of the heart muscle, which dilates and pumps less effectively. Often silent until a sudden arrhythmia or terminal CHF.
Breeds: Doberman Pinscher, Great Dane, Boxer, Labrador Retriever, Golden Retriever, German Shepherd
Congestive heart failure (CHF)
Regardless of cause, any cardiac disease can progress to CHF: the heart no longer pumps effectively and fluid accumulates in the lungs (pulmonary edema) or chest/abdomen. CHF often manifests as persistent nocturnal coughing, labored breathing, or a distended abdomen. It requires urgent treatment.
Breeds with strong predisposition
MVD: small breeds
Cavalier King Charles
Nearly 100% affected by age 10
Dachshund
High frequency after age 7
Toy/Miniature Poodle
Documented predisposition
Yorkshire Terrier
High prevalence
Chihuahua
High prevalence
Miniature Schnauzer
High prevalence
DCM: large breeds
Doberman Pinscher
~50% carriers before age 6 (Holter)
Boxer
Arrhythmogenic DCM (ARVC)
Great Dane
Strong predisposition
Labrador Retriever
Moderate prevalence
Golden Retriever
Moderate prevalence
German Shepherd
Moderate prevalence
Any dog can develop heart disease regardless of breed. Mixed-breed dogs are not immune, but the listed breeds warrant annual echocardiographic screening from adulthood.
Clinical signs
Signs and symptoms
Canine heart disease often progresses silently for months or years. The most common home sign is a persistent nocturnal cough or cough after exertion, frequently mistaken for a respiratory problem.
Early signs
Often underestimated or misattributed
•Fainting or syncopal episodes
•Unusually calm behavior, less interest in play
•Distended abdomen (ascites)
•Swollen limbs (edema)
•Mild cough, especially at night or after exertion
These signs indicate acute cardiac decompensation requiring immediate management.
Open-mouth breathing, uncontrolled panting
"Wet" lung sounds (pulmonary edema)
Blue-tinged gums or mucous membranes (cyanosis)
Sudden collapse or inability to stand
Repeated syncope (several times in a short period)
Uncontrollable vomiting or diarrhea
Intense pain or unusual vocalizations
In an emergency, contact your veterinarian or go to an emergency clinic immediately. Do not leave your dog alone.
A suddenly more frequent, more intense cough, or repeated nighttime awakenings due to coughing should trigger a veterinary call within 24 hours, even if not an immediate emergency.
Diagnosis
How is the diagnosis made?
First indications often arise during a routine exam: heart murmur or arrhythmia detected during auscultation. Additional tests characterize the cardiac disease and guide treatment.
EPICThe EPIC clinical trial (2016) showed that pimobendan (Vetmedin®), started at Stage B2 in Cavalier King Charles Spaniels, delays the onset of CHF by an average of 15 months. An echocardiogram is essential to identify this stage and justify initiating treatment.
1
Echocardiography
The gold standard: cardiac ultrasound measuring chamber size, wall thickness, valve function, and contraction. The only exam that can confirm Stage B2 (ACVIM criteria). Ideally performed by a veterinary cardiologist.
2
Chest X-rays
Evaluation of heart size (vertebral heart scale) and detection of pulmonary edema or pleural effusion. Often the first exam performed in an emergency during respiratory distress.
3
Electrocardiogram (ECG)
Detection of cardiac arrhythmias: ventricular premature contractions (especially in Dobermans and Boxers), tachycardia, conduction blocks. Essential for syncope or suspected arrhythmia.
4
24-hour Holter monitor
Continuous cardiac rhythm recording at home over 24 hours. Particularly useful in Dobermans and Boxers to detect intermittent ventricular arrhythmias that don't appear on a standard ECG.
Treatment is tailored to the type of cardiac disease and ACVIM stage. The goal is to slow progression, prevent CHF, and maintain the best possible quality of life.
Inotropes and vasodilators
Pimobendan (Vetmedin®): strengthens cardiac contraction and dilates vessels; first-line treatment for MVD at Stages B2, C, and D. EPIC trial results.
ACE inhibitors (enalapril, benazepril): vasodilators reducing cardiac workload; often combined with pimobendan at Stages C and D.
Digoxin: strengthens contraction and slows rate; used in some advanced DCM cases or atrial fibrillation.
Caution: pimobendan should not be used with outflow tract obstruction (severe aortic stenosis) without cardiology consultation.
Diuretics and fluid control
Furosemide: first-line diuretic during active CHF; removes excess fluid from lungs or abdomen.
Spironolactone: potassium-sparing diuretic; often combined with furosemide for complementary action and myocardial protection.
Torsemide: more potent furosemide alternative for refractory Stage C and D.
Periodic drainage: thoracocentesis or abdominocentesis for significant refractory effusions.
Rhythm control
Sotalol / mexiletine: antiarrhythmics of choice for ventricular premature contractions in Dobermans and Boxers.
Diltiazem / atenolol: heart rate control in atrial fibrillation or supraventricular tachycardia.
Pacemaker: considered in complete atrioventricular block or symptomatic refractory bradycardia.
Home Holter monitor: assessing antiarrhythmic treatment effectiveness over 24 hours.
Diet and lifestyle
Prescription cardiac diet: reduced sodium to limit fluid retention; do not substitute with a homemade diet without supervision.
Weight management: obesity increases cardiac workload; cachexia (muscle loss) is a sign of decompensation.
Moderate exercise: short regular walks; avoid intense exertion, overheating, and overexcitement.
Dental care: dental infections (tartar, gingivitis) can worsen valvular lesions through chronic bacteremia.
Prognosis
ACVIM stages and prognosis
ACVIM (American College of Veterinary Internal Medicine) guidelines classify canine heart disease into 5 stages. Developed primarily for MVD, this system guides treatment decisions and prognosis.
A
At-risk, no disease yet
At-risk breed with no detectable cardiac abnormality. Annual echocardiographic screening recommended. No treatment needed.
B1
Murmur, no enlargement
Heart murmur present; no cardiac enlargement or clinical signs. No treatment currently recommended. Follow-up echo every 12 months.
B2
Murmur + enlargement, no signs
Murmur + cardiac enlargement, still no clinical signs. ACVIM recommends starting pimobendan (EPIC trial: +15 months before CHF onset). Echo essential to confirm Stage B2.
C
Active or past CHF signs
Active or previously treated CHF. Full medical treatment: pimobendan + diuretics + ACE inhibitors. Median survival 12 to 18 months. Quality of life remains good with rigorous management.
D
Refractory CHF
CHF no longer responding to standard treatment. Intensified or modified protocol. Survival of weeks to months. Palliative care; euthanasia when quality of life is unacceptable.
In Dobermans and Boxers, DCM can first manifest as serious ventricular arrhythmias or sudden death before any CHF signs. Annual Holter screening is recommended from age 3 to 4 years in these breeds.
Home care
Home care
Adapting the environment
Raised, easily accessible food and water bowls (minimize unnecessary effort)
Ramps or gentle steps to access the sofa, bed, or car
Quiet, well-ventilated resting spaces at stable temperature (air conditioning in hot weather)
Limit stairs and jumping: flat terrain preferred
Non-slip surfaces: rugs for walking areas
Avoid overheating: never leave in a vehicle in warm weather
Symptom diary
Nocturnal coughing is often the first sign of decompensation. Count the number of cough episodes per night: more frequent, more productive coughing, or coughs waking the dog are warning signs. Resting respiratory rate (ideally under 30 breaths per minute) is another key indicator to monitor every morning.
Active disease management
Strictly follow all prescribed medications: pimobendan, diuretics, ACE inhibitors
Monitor resting respiratory rate each morning: more than 30/min = call your veterinarian
Count nighttime cough episodes: any sudden increase warrants a consultation
Weigh your dog weekly: sudden weight gain or loss is a warning sign
Limit salt intake: no salty treats, no processed human foods
Moderate physical activity: short regular walks; avoid intense exertion and overexcitement
Regular dental care: chronic tartar maintains bacteremia that can worsen valvular lesions
Close veterinary monitoring: blood tests, echo, blood pressure every 3 to 6 months
Report any new symptom to your veterinarian promptly (increased cough, syncope, etc.)
Monitor every day
Resting respiratory rate (goal: < 30/min)
Nighttime coughing (frequency and intensity)
Appetite and energy level
FAQ
Frequently asked questions
My dog has had a murmur for years without symptoms; do I really need to treat?
It depends on the stage. A murmur alone without cardiac enlargement (Stage B1) does not require medication according to current ACVIM guidelines. However, if echocardiography reveals hypertrophy or dilation (Stage B2), pimobendan is now recommended even without symptoms: the EPIC trial showed it delays CHF onset by an average of 15 months. A murmur on auscultation alone is not enough to define the stage: echocardiography is essential.
What is the difference between mitral valve disease and dilated cardiomyopathy?
Mitral valve disease (MVD) affects the heart valves which progressively leak; it is the cardiac disease of small breeds and represents about 75% of cases. Dilated cardiomyopathy (DCM) affects the heart muscle itself, which weakens and dilates; it is the cardiac disease of large breeds. Basic treatment is similar (pimobendan, diuretics), but DCM is often more insidious as it can manifest as serious arrhythmia or sudden death even before signs of heart failure.
How do I monitor my cardiac dog's breathing at home?
Count breathing movements at rest or during sleep for 30 seconds, then multiply by 2. In a well-treated cardiac dog, resting respiratory rate should stay below 30 breaths per minute. A rate above 30 per minute, or any sudden increase from your usual baseline, should trigger a veterinary call within hours. Mobile apps for respiratory rate tracking exist to facilitate daily monitoring.
My dog has episodes of loss of consciousness; is it the heart or epilepsy?
Cardiac syncopes and epileptic seizures can look similar, but there are important differences. Cardiac syncope often occurs during exertion or strong emotion, lasts a few seconds, and the dog recovers quickly without a prolonged post-ictal phase. An epileptic seizure generally lasts longer, may involve rhythmic involuntary movements, and is often followed by a period of disorientation. An ECG, Holter monitor, and echocardiography can evaluate the cardiac cause.
Is the Doberman really at that high a risk for cardiac problems?
Yes. DCM in Dobermans is particularly serious: approximately 50% of Dobermans develop DCM before age 6 according to some European studies. The disease often remains silent for years (occult stage) then manifests as ventricular arrhythmias that can cause sudden death or rapid CHF. Annual Holter monitoring combined with echocardiography is recommended from age 3 to 4 for all Dobermans.
Can canine heart disease be treated surgically?
In some cases, yes. Congenital pulmonic stenosis can be treated by balloon valvuloplasty (valve dilation without open surgery). Patent ductus arteriosus (PDA) can be closed surgically or by catheterization. A pacemaker can be implanted for complete heart block or bradycardia. MVD and DCM are not surgically correctable with current routine techniques; only medical treatment is available. University centers are exploring surgical valve replacement approaches, but these remain experimental.
This guide is provided for informational and educational purposes only. It does not constitute veterinary medical advice and is not a substitute for a consultation with a qualified veterinarian. Every animal is unique; their health must be evaluated individually. If you have concerns about your dog's health, contact our clinic or consult a veterinarian promptly.
Does your dog have a heart murmur or a nighttime cough?
A cardiac workup can define the precise stage and tailor treatment to maximize your dog's quality and length of life.
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