What Are Heart Murmurs in Dogs?
Heart murmurs in dogs are sounds produced by abnormal blood flow through the heart, altering or muffling the typical lub-dub heartbeat. While common, they typically signal an underlying condition requiring treatment.
The canine heart consists of four chambers: the left and right atria, and the left and right ventricles. Valves between each chamber ensure blood flows in the correct direction at the appropriate time. The blood’s circuit through the body starts with the body itself, moves to the right atrium, passes through the tricuspid valve, enters the right ventricle, goes through the pulmonary valve to the lungs, returns to the heart via the left atrium, flows through the mitral valve to the left ventricle, exits via the aortic valve back to the body, and repeats the cycle.
During a healthy heartbeat, veterinarians using a stethoscope can hear the closing of the mitral and tricuspid valves (lub) and the closing of the aortic and pulmonary valves (dub).
Several factors can cause abnormal blood flow in the heart:
- Irregular valve shape or size
- Obstruction within the valve or chamber
- Backflow of blood due to insufficient valve closure
- Abnormal openings between structures
What Does a Heart Murmur Sound Like?
Using a stethoscope, veterinarians typically hear a typical lub-dub heartbeat in dogs. However, when blood flow is abnormal, the murmur alters or dampens the usual heartbeat sound. Murmurs may manifest as a distinctive “whoosh,” “shoosh,” or continuous muffle. As murmurs progress, the sounds tend to intensify.
Heart Murmur Grades in Dogs
Heart murmurs in dogs are categorized into grades ranging from I to VI, indicating the severity of the condition. As the grade ascends, the murmur becomes more audible, signifying a more advanced disease process.
- Grade I: The mildest form; the murmur is barely detectable with a stethoscope and requires a very quiet environment to be heard.
- Grade II: A soft murmur easily discernible with a stethoscope.
- Grade III: A loud murmur easily heard with a stethoscope on one side of the chest.
- Grade IV: A loud murmur audible on both sides of the chest.
- Grade V: A very loud murmur that can be felt by placing a hand against the chest.
- Grade VI: The most severe grade, with the loudest murmur, palpable through the chest wall and easily audible even without a stethoscope.
Symptoms
Heart murmurs in dogs are indicative of an underlying disease, often accompanied by various symptoms such as:
- Coughing
- Weakness, collapsing, or fainting
- Difficulty tolerating exercise
- Decreased stamina
- Labored breathing at rest
- Paleness or blueness of the gums
- Poor growth
- Weight loss
- Suboptimal oral and dental health
Diagnosis
Veterinarians diagnose heart murmurs in dogs primarily by detecting the sound using a stethoscope during a physical examination. To determine the underlying condition, they utilize the following diagnostic methods:
- X-rays: These help assess the physical size of the heart and provide insight into surrounding organs, such as the lungs.
- Electrocardiograms (ECGs): These detect irregular heartbeats, abnormal heart rates, and arrhythmias.
- Echocardiograms (echos): These pinpoint the location of a heart murmur and, in some cases, reveal the speed and direction of blood flow across valves and within chambers.
- Blood work: This aids in identifying underlying diseases causing murmurs, such as heartworm disease, anemia, and hypothyroidism. Additionally, it helps assess the impact of stress on the heart, potentially worsening the murmur.
Each test result contributes to understanding the puzzle, enabling the veterinarian to identify the underlying issue causing the murmur.
Treatment
Treatment of heart murmurs in dogs revolves around identifying the underlying condition and implementing appropriate measures. To support heart health, a combination of specialized diet, medication, and supportive care is typically prescribed. Veterinarians often recommend regular physical exam visits every six months to monitor the murmur, with additional testing as necessary based on the dog’s condition.
In cases where heart defects are present since birth, surgical correction may be an option. Benign murmurs, commonly found in puppies, often resolve without treatment by around 16 weeks of age. However, monitoring every three to four weeks is advised until resolution to ensure no further complications arise.
For dogs with advanced stages of the disease, heart medications are utilized. These medications aim to promote healthy blood flow, reduce stress on the heart, and enhance its pumping efficiency. Examples include diuretics (such as furosemide), angiotensin-converting enzyme inhibitors (like benazepril or enalapril), and inodilators (such as pimobendan). Medication adjustments are often necessary to tailor the treatment to each individual pet’s needs.
Diet plays a crucial role in promoting pet health, particularly for dogs with advanced heart disease. Specialized diets aimed at reducing sodium and chloride retention and facilitating healthy blood flow are recommended. Veterinarians can provide guidance on selecting the most suitable diet and may prescribe specific formulations as needed.
In cases where underlying diseases like hypothyroidism contribute to the condition, dietary modifications to promote weight loss and regulate thyroid hormones may be necessary. Overall, treatment of heart murmurs in dogs involves a multifaceted approach tailored to address the specific needs and underlying conditions of each individual pet.
Living and Management
Recovery and management of heart murmurs in dogs involve several key factors to promote overall well-being:
- Obesity: Addressing obesity is crucial as it can lead to breathing difficulties and added stress on the heart. A balanced diet coupled with light, regular exercise can support good heart health. However, it’s essential to consult with your veterinarian before implementing any exercise regimen.
- Oral Health: Maintaining proper oral hygiene is vital, as poor oral health has been linked to heart diseases like endocarditis. Regularly brushing your dog’s teeth and addressing dental issues as advised can help prevent tooth decay and related complications.
The prognosis for dogs with heart murmurs varies depending on the underlying cause. In instances of benign puppy murmurs, no treatment is typically necessary, and the prognosis is generally favorable. If the murmur stems from a correctable defect or obstruction, it may resolve following surgical intervention. However, for dogs with advancing heart disease, the prognosis for a murmur can vary significantly based on the specific type of defect and individual circumstances.