HEART MURMUR SIGNS IN DOGS/CATS
WHAT THIS SYMPTOM USUALLY MEANS
A heart murmur is the sound of turbulent blood flow inside the heart. Murmurs can be benign (“innocent”) or indicate structural heart disease, valve problems, or cardiomyopathy. In cats, murmurs are especially concerning because hypertrophic cardiomyopathy (HCM) can remain silent for years.
MOST COMMON CAUSES
MILD OR SELF-LIMITING CAUSES (COMMON)
• Innocent (puppy/kitten) murmurs that fade with age
• Stress-related murmur during anxiety or fear
• Fever temporarily causing faster flow
MEDICAL CAUSES THAT NEED DIAGNOSIS (MODERATE CONCERN)
• Mitral valve disease (very common in small-breed dogs)
• Early cardiomyopathy (common in cats)
• Mild valvular leakage
• Congenital heart defects (PDA, VSD, ASD)
• Anemia (causing rapid blood flow)
• Hyperthyroidism in cats
EMERGENCY CAUSES (HIGH CONCERN)
• Heart failure with fluid in the lungs
• Severe cardiomyopathy (HCM in cats, DCM in dogs)
• Arrhythmias leading to fainting
• Heartworm disease
• Endocarditis (infected heart valve)
RED FLAGS: WHEN THIS IS AN EMERGENCY
• Coughing with rapid breathing
• Blue or gray gums
• Collapse or fainting
• Sudden hind-end weakness (cats, arterial clot)
• Open-mouth breathing (especially cats)
If you’re unsure, treat it as urgent.
AT-HOME CARE YOU CAN START NOW
• Keep activity mild until evaluated
• Avoid overheating or strenuous exercise
• Reduce stress triggers
• Monitor resting respiratory rate
These steps do not replace a veterinary exam if symptoms continue or worsen.
WHAT A VETERINARIAN WILL CHECK
• Careful cardiac auscultation
• Chest X-rays (heart size, lungs)
• Echocardiogram (gold standard)
• ECG for arrhythmias
• Blood pressure
• NT-proBNP in cats to screen for occult heart disease
• Bloodwork for thyroid, anemia, infection
MOST LIKELY DIAGNOSES (BASED ON 40 YEARS OF CASES)
• Mitral valve disease (dogs)
• HCM (cats)
• Innocent murmur in young animals
• Congenital defects
• Heartworm disease
• Anemia-related flow murmur
BREEDS OR AGES AT HIGHER RISK
• Cavalier King Charles Spaniels (MVD)
• Small-breed senior dogs
• Maine Coons, Ragdolls (HCM)
• Senior cats
• Boxers, Dobermans (DCM-related murmurs)
WHEN YOU SHOULD SCHEDULE A VETERINARY VISIT
Emergency:
• Murmur + breathing difficulty, fainting, blue gums
Within 24–72 hours:
• Newly diagnosed murmur without red flags
• Increased coughing or rapid breathing in a known heart patient
Routine recheck:
• Stable mild murmurs in healthy pets
EXPECTED RECOVERY TIME
• Innocent murmurs: may resolve in weeks
• MVD: chronic but manageable
• Cardiomyopathy: long-term management
• Arrhythmia-related murmurs: may improve with therapy
HOW THIS SYMPTOM RELATES TO LONGEVITY
Early detection preserves quality of life. With appropriate medications and monitoring, many pets with heart murmurs enjoy years of excellent, active life. Ignoring murmurs risks sudden progression to heart failure.
WHEN TO CONSIDER A LONGEVITY CONSULT
Any pet with a newly diagnosed murmur, or worsening signs, benefits from a longevity plan tailored to heart protection and lifestyle adjustments.
FOR CANCER-RELATED CONCERNS
Rarely, heart tumors or metastatic disease cause murmurs or secondary heart changes. If imaging shows masses, use Pet Cancer Navigator.
FAQ
Does a murmur always mean heart failure?
No—many murmurs are mild or benign.
Can a murmur appear suddenly?
Yes, especially with anemia or infection.
Can a murmur get worse over time?
Yes—valve disease often progresses.