A Heart Murmur In Cats is not a disease itself, but rather an abnormal heart sound that veterinarians detect when listening to a cat’s heart with a stethoscope. This unusual sound often indicates an underlying heart condition, frequently involving issues with the heart valves, leading to turbulent blood flow.
Typically, a healthy feline heart produces two distinct sounds during each beat. The presence of an additional sound, often described as a “whooshing” noise, signifies a heart murmur. Heart murmurs are relatively common in cats, particularly in middle-aged and senior felines.
While more frequently diagnosed in older cats, heart murmurs can also occur in younger cats. In kittens and young cats, a heart murmur might raise concerns about congenital heart defects, which are conditions present from birth. However, it’s important to note that congenital heart issues are relatively rare in cats.
The characteristic “whooshing” sound of a heart murmur arises from turbulent blood flow within the heart. In a healthy heart, blood moves smoothly through its four chambers and across the valves that separate these chambers. When there are obstructions or irregularities in this flow, turbulence occurs, disrupting the normal “lub-dub” heart sounds.
This turbulent blood flow can be caused by various factors, including malfunctioning heart valves, structural abnormalities like holes in the heart walls or arteries, or constrictions in blood vessels or heart chambers. Additionally, conditions causing rapid heart rates or decreased blood viscosity, such as anemia in cats, can also lead to heart murmurs.
Heart murmurs in cats are categorized based on three key characteristics:
- Grade: This refers to the loudness of the murmur.
- Configuration: This describes when the murmur is loudest during the heart’s contraction (systole) and relaxation (diastole) phases.
- Location: This indicates where the murmur is heard most clearly when listening with a stethoscope on the cat’s chest.
Veterinarians use a grading scale from I to VI to classify heart murmurs in cats based on their loudness. This is a subjective assessment determined by the veterinarian’s auditory perception through a stethoscope. The grades are defined as follows:
- Grade I Heart Murmur: Very faint, often only detectable by a highly trained veterinarian in a quiet environment.
- Grade II Heart Murmur: Soft, but consistently audible.
- Grade III Heart Murmur: Moderately loud, considered an intermediate grade and the most commonly diagnosed.
- Grade IV Heart Murmur: Loud murmur, radiating widely across the chest, often heard on both sides.
- Grade V Heart Murmur: Very loud, accompanied by a palpable “thrill” or vibration felt through the chest wall.
- Grade VI Heart Murmur: Extremely loud, audible even before the stethoscope makes full contact with the chest, and typically associated with a pronounced “thrill.”
It’s crucial to understand that a benign or innocent heart murmur can sometimes sound very similar to a murmur caused by severe heart disease. Therefore, any heart murmur detected in a cat necessitates a thorough veterinary evaluation to ensure the cat’s cardiac health.
Pinpointing the precise location of a heart murmur in cats can be challenging due to their small chest size. Murmurs are frequently best auscultated along the sternum (breastbone).
The grade, location, and configuration of a heart murmur provide valuable clues to help veterinarians determine the underlying cause.
Heart murmurs in cats can be broadly classified as either congenital or acquired. Congenital heart murmurs are present at birth or shortly thereafter, typically linked to structural heart defects. These murmurs might be subtle initially and become more apparent as the cat grows and matures.
Acquired heart murmurs, on the other hand, develop at any stage of a cat’s life. They can be benign, meaning they are not associated with any underlying heart disease, or they can be indicative of acquired heart conditions, such as hypertrophic cardiomyopathy (HCM) in cats.
Some heart murmurs are classified as “innocent” or benign. These murmurs are not caused by any underlying structural heart disease and are often intermittent and quiet. They can occur in cats of any age.
Alt text: A veterinarian attentively listens to a senior cat’s heart with a stethoscope during a check-up, highlighting the routine detection of heart murmurs in feline patients.
Symptoms of Heart Murmur in Cats
Often, cat owners won’t observe any noticeable symptoms in cats with heart murmurs until the underlying heart disease progresses significantly. Symptoms typically emerge when the condition leads to congestive heart failure or thromboembolism (blood clots).
In many cases, heart murmurs are discovered incidentally during routine veterinary check-ups. When a murmur is detected, your veterinarian will discuss potential causes and recommend the next diagnostic steps.
Signs of advanced heart disease, heart failure, and thromboembolism in cats can include:
- Unexplained weight loss or muscle wasting.
- Reduced appetite.
- Increased hiding or withdrawal behavior.
- Generalized weakness.
- Coughing or wheezing sounds.
- Exercise intolerance, such as excessive panting even with minimal activity.
- Elevated respiratory rate at rest.
- Labored breathing or increased effort to breathe.
- Discharge from the mouth or nostrils.
- Changes in gum color to pale blue, gray, or white.
- Lethargy or marked decrease in energy levels.
- Sudden collapse.
- Paralysis, particularly of the hind limbs.
- Painful vocalization.
- In kittens with severe congenital heart defects, stunted growth may be observed.
Causes of Heart Murmur in Cats
A heart murmur in a cat can stem from a wide range of underlying health issues. Common causes include:
- Anemia (low red blood cell count).
- Stress or anxiety, which can temporarily increase heart rate and create a murmur.
- Hypertension (high blood pressure).
- Underlying heart disease.
- Hypertrophic cardiomyopathy (HCM), the most common heart disease in cats.
- Structural heart defects such as holes in the heart walls (atrial or ventricular septal defects).
- Heart valve abnormalities, including deficiencies of the mitral, tricuspid, or aortic valves.
- Stenosis (narrowing) of heart valves: subaortic, aortic, mitral, tricuspid, or pulmonic valves.
- Patent ductus arteriosus (PDA), a congenital defect where a fetal blood vessel fails to close after birth.
- Tetralogy of Fallot, a complex set of congenital heart malformations.
- Thromboemboli (blood clots) within the heart or major blood vessels.
- Heartworm disease.
- Endocarditis, an infection of the inner lining of the heart chambers and valves.
Certain cat breeds have a higher predisposition to specific heart conditions that can cause murmurs. For example, Maine Coon cats are known to be prone to severe forms of HCM, including hypertrophic obstructive cardiomyopathy (HOCM). Persian cats, American Shorthairs, and British Shorthairs are also more susceptible to less severe inherited HCM. Siamese cats have an increased incidence of congenital PDA and inherited dilated cardiomyopathy (DCM).
Alt text: A veterinary technician carefully measures a cat’s blood pressure using specialized equipment, illustrating a common diagnostic procedure that may be recommended when investigating heart murmurs.
How Veterinarians Diagnose Heart Murmur in Cats
While a veterinarian’s initial stethoscope examination is crucial for detecting a heart murmur and assessing its characteristics (location, configuration, and grade), it’s usually not sufficient to determine the underlying cause.
It’s important to reiterate that benign or innocent heart murmurs can sound very similar to those caused by serious heart conditions. Therefore, a comprehensive evaluation is essential for any cat diagnosed with a heart murmur.
Typically, veterinarians will recommend a complete blood panel, including a cardiac proBNP test. The proBNP test measures a substance released by the heart muscle when it’s stretched or strained. Elevated proBNP levels can be a strong indicator of underlying heart disease in cats.
Blood work also helps to rule out other conditions that can contribute to or mimic heart disease, such as anemia or systemic illnesses like hyperthyroidism in cats.
Chest X-rays (radiographs) are frequently recommended to visualize the size and shape of the heart, assess the major blood vessels connected to the heart, and examine the lungs for any signs of fluid buildup, which is indicative of congestive heart failure (CHF).
Echocardiography, or ultrasound of the heart, is considered the gold standard for diagnosing the underlying cause of a heart murmur. This non-invasive imaging technique provides detailed pictures of the heart’s structure and function. In some cases, if an irregular heart rhythm is suspected, an electrocardiogram (EKG) may also be recommended.
Treatment of Heart Murmur in Cats
The heart murmur itself is not the target of treatment; rather, the focus is on addressing the underlying cause of the murmur.
Treatment strategies vary widely depending on the diagnosis, the severity of the condition, and the cat’s overall health. Benign or innocent heart murmurs generally do not require any treatment. When considering treatment for heart disease in cats, factors such as the cat’s age, overall health status, and the financial implications of therapy are important considerations.
Congestive heart failure (CHF) often necessitates hospitalization, especially in severe cases. Treatment for CHF typically involves diuretics (like furosemide), cardiac medications (such as benazepril), and oxygen therapy. Pleural effusion, fluid accumulation around the lungs, is a common complication of CHF in cats and may require thoracocentesis, a procedure to drain the fluid and allow the lungs to re-expand.
Some congenital heart defects, like small septal defects (holes in the heart walls), may spontaneously resolve as the kitten grows. In certain cases of congenital heart disease, surgical intervention may be necessary to correct conditions like PDA or septal defects.
Treating underlying conditions such as anemia or hyperthyroidism can also lead to the resolution or improvement of associated heart murmurs.
Each case is unique, and your veterinarian will develop a tailored diagnostic and treatment plan for your cat, taking into account the specific circumstances and discussing the prognosis.
Recovery and Management of Heart Murmur in Cats
Ongoing monitoring of heart murmurs and any associated heart disease is crucial to track the condition’s progression. Management of CHF and congenital heart issues in cats involves regular veterinary re-examinations (typically every few months), periodic blood work, and chest X-rays to assess the cat’s stability and determine if medication adjustments are needed.
The prognosis for cats with heart murmurs varies widely depending on the underlying cause. Benign heart murmurs carry an excellent prognosis, while severe congenital or acquired heart diseases often have a more guarded to grave prognosis.
Long-term prognosis is dependent on the specific cause of the heart murmur and the cat’s response to treatment. In many cases of feline heart disease, the focus of management is not on a cure, but rather on maintaining the cat’s quality of life and comfort for as long as possible.
Heart Murmur in Cats FAQs
Do all heart murmurs in cats sound the same?
No. Heart murmurs are diverse in their characteristics. They differ in grade (loudness), configuration (timing within the heartbeat cycle), and location where they are best heard on the chest.
What is the prognosis for cats with a heart murmur?
The prognosis is highly variable and depends entirely on the underlying cause of the heart murmur. Innocent murmurs typically have an excellent prognosis, while murmurs associated with significant heart disease carry a more guarded or poor prognosis. The long-term outlook will also depend on how well your cat responds to any necessary treatments.
What is an “innocent murmur” in cats?
“Innocent” or benign heart murmurs are abnormal heart sounds that are not caused by any structural heart disease. They are relatively common in cats of all ages, often intermittent, and typically quiet when auscultated with a stethoscope. An echocardiogram is needed to definitively confirm an innocent heart murmur and rule out underlying structural heart disease.
WRITTEN BY
Katie Grzyb, DVM
Veterinarian
Dr. Katie Grzyb received her Doctorate of Veterinary Medicine from Ross University in 2009. She continued her clinical training at…
