Heart Disease in Cats & Dogs

Written by Shula Berg BVSc CertAVP(GSAS) GPAdvCert(SASTS) MRCVS
Clinically reviewed by Elizabeth McLennan-Green BVM&S CertAVP(SAM) MRCVS

Table of Contents

- Overview
- Symptoms
- Diagnosis
- Next Steps

What is heart disease and what causes it?

Your vet may have identified signs of heart disease in your cat or dog and advised investigation. This is most commonly a heart murmur or irregular rhythm heard on auscultation.  

When we listen to the heart with a stethoscope, we hear two noises for each heartbeat as the heart valves close. A heart murmur describes noise present in addition to the normal heart sounds, caused by turbulent blood flow. The character and location of a murmur can give us a clue about what exactly is causing it, however only a heart scan can provide a definite diagnosis. 

Murmurs are graded from 1 to 6, with a grade 1 murmur being barely audible, and a grade 6 murmur being much louder than the heart sounds. The volume or grade of a murmur does not necessarily correlate with the changes present, and we cannot assume that a quiet murmur is not a problem. 

Common causes of murmurs: 

  • A valve leaking
  • A narrow vessel
  • A change to the shape or thickness of the heart chambers

What are the symptoms of heart disease?

Heart disease is common in older pets; however, many animals show no symptoms until they develop heart failure. This is why regular check-ups and early investigation are so important. Some animals will show signs such as slowing down, reduced exercise tolerance, coughing, or collapsing episodes. Often medication can help slow down changes, improving and prolonging quality of life, however without an accurate diagnosis we cannot know what will help. 

What tests are used to diagnose heart disease in cats and dogs?

Further diagnostics are important to find out the cause of the murmur and determine whether treatment is needed. Usually this requires referral to a specialist cardiologist, or a vet with a certificate or particular interest in cardiology. They will assess your pet and discuss a plan with you, but investigation is likely to include some or all of the following: 


Often called an echo, this is an ultrasound scan of the heart. It allows direct visualisation of the chambers and valves that make up the heart, along with measurement of the contractility, blood flow and valve function. 

An echo is performed with the animal awake or under light sedation. It requires some hair to be clipped from the chest but is not painful. Your pet will be asked to lie on a cushioned table in a dark room; it is not uncommon for pets to fall asleep during the scan! 

Blood pressure measurement

Blood pressure is closely linked to the heart's activity. Heart disease can cause low blood pressure, or abnormally high blood pressure if the body is compensating for changes. If untreated this can cause damage to other organs. 

Electrocardiography (ECG) 

An ECG is an electrical trace of the heart's activity. It is recorded over a few minutes and shows any rhythm disturbances (known as arrhythmias). Some arrhythmias are audible as an irregular heartbeat; however, some are subtle and only identifiable on an ECG. 


If the heart is not pumping blood around the body effectively, fluid can build-up in or around the lungs. Ultrasound is not good at examining the lungs so an x-ray may be recommended. 

General blood tests 

Blood tests are a general screen and can identify underlying diseases or organ damage. Checking organ function may be recommended before starting some medications. 

What are the next steps for pets with heart disease?

Once the cardiologist has completed the diagnostic tests, they will be able to explain the changes present in your pet's heart, whether treatment is required, and advise you of the expected progression of any disease present. 


Please note that the content made available on this webpage is for general information purposes only. Whilst we try to ensure that at the time of writing all material is up to date and reflects industry standards, we make no representation, warranties or guarantees that the information made available is up to date, accurate or complete. Any reliance placed by yourselves is done so at your own risk.

Page last reviewed: 16th January 2024
Next review due: 16th January 2026