A heart murmur in cats is an atypical sound detected when a veterinarian listens to your cat’s heart using a stethoscope. These unusual heart sounds often indicate an underlying health issue, frequently involving the heart valves and causing turbulent blood flow.
Typically, a healthy feline heart produces two distinct sounds. The presence of an additional sound or a “whooshing” noise during the heartbeat signifies a heart murmur. Heart murmurs are relatively common, particularly in middle-aged to senior cats.
While more frequently observed in older cats, heart murmurs can also occur in younger cats. In kittens and young cats, they may raise concerns about congenital heart defects, which are conditions present from birth. However, congenital heart issues are less common than acquired murmurs developing later in life.
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 between these chambers. When obstructions or irregularities exist, this smooth flow becomes turbulent, altering the typical “lub-dub” heart sounds.
This turbulence 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. Furthermore, rapid heart rates due to excitement or conditions causing blood thinning, such as anemia, can also lead to turbulent blood flow and murmurs.
Heart murmurs in cats are categorized based on three key characteristics:
- Grade: This refers to the loudness or intensity of the murmur.
- Configuration: This describes when the murmur is most audible during the cardiac cycle—either during systole (contraction) or diastole (relaxation).
- Location: This indicates where on the chest the murmur is heard most clearly with a stethoscope.
Veterinarians use a grading scale from 1 to 6 to classify heart murmurs based on their loudness. This is a subjective assessment determined by the veterinarian’s auditory perception while listening to the cat’s heart. The grades are defined as follows:
- Grade I Heart Murmur: Very faint and difficult to hear; often only detectable by a highly experienced veterinarian in a quiet environment.
- Grade II Heart Murmur: Soft but readily audible murmur.
- Grade III Heart Murmur: A murmur of moderate intensity, considered intermediate in loudness and the most frequently diagnosed grade.
- Grade IV Heart Murmur: A louder murmur that can be heard radiating across different areas of the chest, often audible on both sides.
- Grade V Heart Murmur: A loud murmur accompanied by a palpable “thrill,” a vibration felt when touching the chest wall over the heart.
- Grade VI Heart Murmur: The loudest grade of murmur, audible even before the stethoscope makes full contact with the chest. It is also associated with a pronounced palpable “thrill.”
It’s important to note that benign or innocent heart murmurs can sometimes sound similar to those caused by serious heart conditions. Therefore, any detected heart murmur necessitates a thorough veterinary evaluation to ascertain your cat’s cardiac health.
Locating the precise origin of a heart murmur in cats can be challenging due to their small chest size. Murmurs are frequently best auscultated along the sternum.
The grade, location, and configuration of a heart murmur collectively provide valuable clues to help diagnose the underlying cause.
Heart murmurs can be classified as either congenital or acquired. Congenital heart murmurs are present at birth or shortly thereafter and are typically linked to structural heart defects. These murmurs may be subtle initially and become more apparent as the cat grows and matures.
Acquired heart murmurs develop at any stage of life. They may be benign, indicating no underlying heart disease, or they could be indicative of significant cardiac conditions like hypertrophic cardiomyopathy (HCM) in cats.
Certain heart murmurs are deemed “innocent” or benign. These murmurs are not associated with any heart disease. They are commonly found in cats of all ages, tend to be intermittent—meaning they come and go—and are generally quiet when auscultated with a stethoscope.
Symptoms of Heart Murmurs in Cats
Often, cat owners will not observe any outward signs of a heart murmur until the underlying heart condition progresses significantly. Symptoms typically emerge only when heart disease advances to stages of congestive heart failure or thromboembolism (blood clot formation).
Heart murmurs are usually discovered incidentally during routine veterinary check-ups. Upon detecting a murmur, your veterinarian will discuss potential causes and recommend further diagnostic steps.
Symptoms that may indicate advanced heart disease, heart failure, or thromboembolism include:
- Unexplained weight loss or muscle wasting
- Reduced appetite
- Increased hiding behavior or withdrawal
- General weakness or lethargy
- Coughing or wheezing sounds
- Exercise intolerance, such as excessive panting after minimal activity
- Elevated resting respiratory rate (tachypnea)
- Labored breathing or increased respiratory effort (dyspnea)
- Discharge from the mouth or nostrils
- Bluish, gray, or pale white gums (cyanosis)
- Lethargy and decreased activity
- Sudden collapse
- Hind limb paralysis (often sudden and painful)
- Painful vocalization
- Stunted growth in kittens with severe congenital heart defects
Causes of Heart Murmurs in Cats
Heart murmurs in cats can arise from a range of underlying health conditions, including:
- Anemia (low red blood cell count)
- Stress or Anxiety, which can cause a temporary increase in heart rate and flow.
- Systemic Hypertension (High Blood Pressure)
- Underlying Heart Disease
- Hypertrophic Cardiomyopathy (HCM), the most common heart disease in cats.
- Congenital heart defects such as:
- Atrial or Ventricular Septal Defects (holes in the heart walls)
- Heart valve abnormalities including:
- Mitral valve dysplasia
- Tricuspid valve dysplasia
- Aortic valve dysplasia
- Stenosis (narrowing) of heart valves or outflow tracts:
- Subaortic stenosis
- Aortic stenosis
- Mitral stenosis (rare)
- Tricuspid stenosis (rare)
- Pulmonic stenosis
- 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 vessels.
- Heartworm Disease
- Endocarditis (infection of the inner lining of the heart 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 and hypertrophic obstructive cardiomyopathy (HOCM). Persian cats, American Shorthair cats, and British Shorthair cats are also predisposed to less severe inherited HCM. Siamese cats have a higher incidence of congenital PDA and inherited dilated cardiomyopathy (DCM).
Diagnosing Heart Murmurs in Cats
While a stethoscope examination is crucial for detecting a heart murmur and helps in assessing its location, configuration, and grade, it is usually insufficient to determine the underlying cause.
Since benign or innocent heart murmurs can sound very similar to those caused by serious heart conditions, comprehensive veterinary 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 hormone released by the heart when it is stretched or stressed, providing a quantifiable value related to cardiac muscle strain. Elevated ProBNP levels, especially when correlated with clinical signs, can strongly suggest underlying heart disease.
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.
Chest radiographs (X-rays) are frequently recommended to evaluate heart size and shape, examine the major blood vessels connected to the heart, and assess the lungs for signs of fluid accumulation indicative of congestive heart failure (CHF).
Echocardiography, or ultrasound of the heart, is considered the gold standard for diagnosing the cause of a heart murmur. This non-invasive imaging technique provides detailed visualization of the heart’s structure and function. In some cases, if an irregular heart rhythm (arrhythmia) is detected, an electrocardiogram (ECG or EKG) may also be recommended.
Treatment Options for Cat Heart Murmurs
A heart murmur itself is not treated directly. Instead, treatment focuses on addressing the underlying cause of the murmur, if one is identified and requires intervention.
The approach to treatment varies widely depending on the underlying diagnosis, the severity of the condition, and the cat’s overall health status. Benign or innocent murmurs typically require no treatment. When heart disease is present, factors such as the cat’s age, general health, and the financial implications of treatment are important considerations.
Congestive heart failure (CHF), depending on its severity, often necessitates hospitalization and intensive care. Treatment for CHF may include diuretics (like furosemide) to reduce fluid overload, cardiac medications (such as benazepril) to support heart function, and oxygen therapy to improve breathing. In many CHF cases, pleural effusion (fluid accumulation around the lungs) requires removal via a procedure called thoracocentesis to allow for proper lung expansion.
Some congenital heart defects, such as small septal defects, may spontaneously resolve as the kitten grows, sometimes closing within the first six months of life. However, other congenital conditions, like PDA or significant septal defects, may require surgical intervention to correct the structural abnormality.
Treating underlying conditions like anemia or hyperthyroidism may 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, considering your cat’s specific needs and prognosis.
Recovery and Long-Term Management of Heart Murmurs in Cats
Ongoing monitoring is crucial for cats with heart murmurs, particularly those with diagnosed heart disease, to track the progression of the condition. Management of CHF and congenital heart issues involves regular veterinary re-evaluations, typically every few months. These check-ups may include blood work and chest X-rays to monitor stability and guide adjustments to medication or the need for additional treatments.
The prognosis for cats with heart murmurs varies significantly. For benign murmurs, the prognosis is generally excellent. However, for murmurs associated with severe congenital or acquired heart disease, the prognosis can be grave.
Long-term prognosis is highly dependent on the underlying cause of the heart murmur and the cat’s response to treatment. In many cases of feline heart disease, the focus shifts from a potential cure to managing the condition to maximize the cat’s quality of life and comfort.
Frequently Asked Questions About Heart Murmurs in Cats
Do all cat heart murmurs sound alike?
No, heart murmurs are diverse. They differ in grade (loudness), configuration (timing within the heartbeat cycle), and location on the chest where they are best heard.
What is the outlook for a cat with a heart murmur?
The prognosis is variable and depends heavily on the underlying cause of the heart murmur. Benign murmurs typically carry an excellent prognosis, while those linked to severe heart disease often have a guarded to poor prognosis. The individual cat’s response to treatment also significantly impacts the long-term outlook.
What is considered an “innocent” heart murmur in cats?
“Innocent” or benign heart murmurs are abnormal heart sounds that occur in the absence of any underlying heart disease. These murmurs are relatively common in cats of all ages, are often intermittent, and are usually soft in intensity. Definitive confirmation of an innocent murmur typically requires an echocardiogram (cardiac ultrasound).
WRITTEN BY:
Katie Grzyb, DVM
Veterinarian
Dr. Katie Grzyb earned her Doctorate of Veterinary Medicine from Ross University in 2009 and completed her clinical training at…
