Home » Diseases » In dogs » Myocardial Tumors (Heart Muscle Tumors)

Myocardial Tumors (Heart Muscle Tumors) in Dogs

Occurrence: very rare
Location of disease: Chest

Author: Dr. med. vet. Gisa Löwe | Last modified: 17.02.2026

When to visit the vet?

Non-urgent see a veterinarian within 2–3 days

If the condition worsens / symptoms persist, consult a veterinarian.

Definition

Myocardial tumors, also called heart muscle tumors, are abnormal growths in the heart muscle tissue of dogs. These tumors can be benignBenign refers to a non-invasive, non-serious condition that is not life-threatening. In medicine, the term is often used to describe benign tumors that do not metastasize, meaning they do not form secondary tumors. or malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. and vary in their growth rate and effects on heart function.

The most important facts at a glance

Myocardial tumors in dogs are rare but serious diseases that affect the heart muscle. These tumors can arise primarily in the heart or reach it secondarily through metastasesA metastasis is a secondary tumor that originates from a primary, malignant tumor in another part of the body. Metastases indicate that cancer has spread in the body. from other parts of the body. The exact causes are unclear; however, genetic factors, environmental conditions, and possibly chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. inflammation play a role. Symptoms include cardiac arrhythmias, cough, reduced exercise tolerance, and in severe cases, shortness of breath or cardiovascular collapse. DiagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. is made through clinical examinations and imaging procedures such as ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. and X-rayX-ray is an imaging technique that uses X-rays to create images of the inside of the body. It is often used to diagnose bone fractures, lung diseases, and other conditions., supplemented by ECGs and possibly biopsies.

Treatment depends on the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. type, size, and the dog’s health condition. Options include surgery, chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells., and radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue., although removal of a tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. is often complicated. Symptomatic support to improve heart function may also be necessary. The prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. varies greatly, with benignBenign refers to a non-invasive, non-serious condition that is not life-threatening. In medicine, the term is often used to describe benign tumors that do not metastasize, meaning they do not form secondary tumors. tumors offering better prospects than malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. ones. Without treatment, myocardial tumors can quickly lead to heart failure, and even with treatment, life expectancy is often limited.

Preventive measures are limited, as the exact causes are not known. Regular veterinary check-ups and a healthy lifestyle can help minimize the risk. Research is focusing on genetic and molecular foundations as well as the development of new diagnostic and treatment methods, including noninvasive techniques and immunotherapies.

Causes

A dog’s heart consists of four chambers: two atria and two ventricles. The heart muscle, also called the myocardiumThe myocardium is the heart muscle itself, responsible for the heart's contraction, which enables blood circulation in the body. Diseases of the myocardium can impair the heart's pumping function., is responsible for pumping blood through the body. A disruption in this system, such as that caused by the appearance of a tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions., can impair the efficiency of the heartbeat and lead to a variety of cardiovascular problems.

Myocardial tumors are relatively rare in dogs, but when they occur, they can have significant health impacts. Science distinguishes two main types of tumors in the heart muscle: primaryPrimary refers to the first or original cause of a disease or condition, as opposed to secondary causes or symptoms that develop from it. tumors, which originate directly in the heart, and secondary tumors, which spread from other parts of the body. PrimaryPrimary refers to the first or original cause of a disease or condition, as opposed to secondary causes or symptoms that develop from it. tumors are rarer, while secondary tumors are more common, as they can affect the heart as part of a metastatic process.

The exact causes of myocardial tumors in dogs are not yet fully understood. It is believed that genetic factors play a role, particularly in certain dog breeds that are more susceptible to heart disease. Environmental factors, such as exposureExposure refers to the Contact with or subjection to certain substances, environmental factors, or pathogens. In veterinary medicine, this can include Contact with toxins, allergens, or infectious agents that can cause health problems in dogs and cats. to certain chemicals or radiation, may also increase the risk. In some dogs, pre-existing conditions or a weakened immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. may promote the development of tumors.

A possible cause of myocardial tumors could also be chronicChronic refers to a condition or disease that is long-lasting or permanent. Chronic diseases often develop slowly and can lead to persistent or recurring health problems over time. inflammation of the heart tissue. Long-term inflammation can lead to cellularCellular refers to cells or consisting of cells. In biology and medicine, it refers to processes, structures, or functions that occur at the level of individual cells. changes that ultimately promote tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. growth. In some dogs, a connection between certain infections and the development of heart tumors is also suspected, although this is rare and requires further research.

Symptoms

Very common symptoms:

Common symptoms:

Rare symptoms:

The symptoms of myocardial tumors in dogs can be subtle and vary depending on the location and size of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions.. Some dogs may show no obvious signs until the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. has reached a considerable size.

Common symptoms include shortness of breath, cough, lethargy, and reduced exercise tolerance. These symptoms result from the impaired pumping capacity of the heart, which leads to insufficient oxygen supply to the body. Some dogs may also experience fainting or weakness episodes, especially after physical exertion.

In advanced cases, fluid accumulation in the abdomenThe abdomen, also known as the abdominal cavity, is the part of the body located between the rib cage and the pelvis. It houses several important organs, including the stomach, liver, kidneys, intestines, and spleen. (ascitesAscites refers to the accumulation of free fluid in the abdominal cavity, which can lead to visible abdominal distension. It can be caused by various diseases, including liver disease, cancer, or heart failure.) or chest (pleural effusion) may occur, leading to visible swelling and respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress. Other signs may include heart murmurs, irregular heartbeat, or even sudden collapse and death.

Diagnosis

The diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. of myocardial tumors usually begins with a thorough clinical examination and a detailed medical historyThe medical history is the systematic collection of a patient's medical history through questioning. It includes information about previous illnesses, treatments, allergies, and lifestyle habits.. The veterinarian will look for signs of heart failure and other symptoms that could indicate a heart problem.

Imaging procedures are crucial for diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients.. A cardiac ultrasoundUltrasound refers to sound waves that are above the hearing threshold of the human ear. In medicine, ultrasound is used for diagnostic imaging procedures to visualize internal organs, tissues, and blood flow. (echocardiogram) can help assess the structure and function of the heart and identify tumors in the heart muscle. X-rays of the chest can also be used to detect changes in the heart or surrounding area, such as fluid accumulation.

Additional tests such as an electrocardiogramSee ECG. (ECG) can reveal irregular heart rhythms caused by a tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions.. In some cases, magnetic resonance imaging (MRI)Magnetic resonance imaging is an imaging technique that uses strong magnetic fields and radio waves to create detailed images of the inside of the body. It is used in veterinary medicine to diagnose diseases of the brain, spine, and other organs. or computed tomography (CT)Computed tomography (CT) is an imaging technique that uses X-rays and computer technology to create cross-sectional images of the body. It enables a detailed view of bones, organs, and other structures and is used for the diagnosis of injuries, diseases, and for planning medical interventions. may be required to obtain a more accurate representation of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions.. A biopsyA biopsy is a medical procedure in which a small amount of tissue is removed from the body to be examined under a microscope for signs of disease. Biopsies can help diagnose cancer and other conditions. of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. tissue can be performed to determine the type of tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions., although this can be risky during heart surgery.

Therapy

The treatment of myocardial tumors depends on the type of tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions., its size and location, and the overall health of the dog. Treatment options include surgical procedures, chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells., and radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue..

If the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. is operable, surgical removal may be considered. However, this option is often complicated and risky, as the heart is a delicate organ and the surgery itself can be life-threatening. In many cases, complete removal of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. may not be possible.

ChemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. can help slow or stop the growth of the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions., especially in malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. tumors. The selectionSelection refers to the process of natural or artificial selection of specific individuals for reproduction, based on desired genetic traits. In breeding, this is applied to promote specific characteristics in dogs and cats. of medications and the duration of treatment depend on the type of tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. and the dog’s response to therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions..

Radiation therapyRadiation therapy is the use of radiation, most often to treat cancer. It can be used to kill cancer cells or slow their growth without significantly damaging surrounding healthy tissue. can be used in some cases, especially when the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. cannot be surgically removed. This therapyTherapy refers to the treatment of diseases or disorders with the aim of alleviating symptoms, promoting healing, or improving quality of life. Therapies can be medicinal, surgical, or through other medical interventions. aims to destroy the tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. cells and control growth.

In addition to specific tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. treatment, symptomatic support may be important. Medications to support heart function, such as diureticsDiuretics are medications that increase urine production in the kidneys to rid the body of excess salt and water. They are often used to treat high blood pressure, heart failure, and certain types of edema. and ACE inhibitors, can help relieve symptoms and improve the dog’s quality of life.

Prognosis and follow-up care

The prognosis for dogs with myocardial tumors varies greatly and depends on various factors, including the type of tumor, its size, location, and the stage of the disease at the time of diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients..

BenignBenign refers to a non-invasive, non-serious condition that is not life-threatening. In medicine, the term is often used to describe benign tumors that do not metastasize, meaning they do not form secondary tumors. tumors that can be successfully removed offer a better prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. than malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. tumors, which are often more aggressive and can form metastasesA metastasis is a secondary tumor that originates from a primary, malignant tumor in another part of the body. Metastases indicate that cancer has spread in the body.. Unfortunately, malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. tumors in the heart are often difficult to treat, and the long-term prognosisThe prognosis is the prediction of the likely course and outcome of a disease based on the general state of health, the nature of the disease, and the response to treatment. It can provide information on how a disease is expected to develop. is unfavorable in many cases.

Without treatment, myocardial tumors can quickly lead to heart failure. Even with treatment, life expectancy is often limited, with the dog’s quality of life being the priority. In some dogs, however, early detection and treatment can prolong life and relieve symptoms.

Prevention

Since the exact causes of myocardial tumors are not fully known, there are no specific preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. measures. However, general health care and regular veterinary examinations can help detect and treat health problems early.

A balanced diet, regular exercise, and avoidance of environmental toxins can contribute to the overall health of the dog and possibly reduce the risk of developing tumors. In dogs with a genetic predispositionA predisposition is an innate inclination or susceptibility of an organism to certain diseases or conditions. In dogs and cats, there may be a genetic predisposition to certain conditions such as hip dysplasia or certain heart diseases. to heart disease, regular monitoring by a veterinarian may be useful to enable early intervention.

It is also important to pay attention to the health of the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body., as a strong immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. can help reduce the risk of tumor development. Vaccinations and parasite control should be kept up to date to avoid infections that could weaken the immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body..

Outlook on current research

Research on myocardial tumors in dogs has made progress in recent years as understanding of the pathophysiologyPathophysiology deals with the changes in physiological processes caused by diseases or injuries. It examines how these changes lead to the symptoms and signs of a disease. of this disease grows. Scientists are focusing on better understanding the genetic and molecular basis of heart muscle tumors to develop earlier diagnostic methods and more effective treatment strategies. One of the main directions is the investigation of genetic abnormalities that can promote the growth of tumors in the heart muscle. It is believed that certain genetic mutations in dogs can increase the risk of developing myocardial tumors. These genetic markers could play a role in early detection in the future.

Another area of research is the development of noninvasive diagnostic tools. Currently, imaging procedures such as ultrasound and MRI are the main methods for diagnosing myocardial tumors. Researchers are working to improve these techniques to detect smaller tumors earlier and characterize them more accurately. Advances in imaging technology could enable more precise differentiation between benignBenign refers to a non-invasive, non-serious condition that is not life-threatening. In medicine, the term is often used to describe benign tumors that do not metastasize, meaning they do not form secondary tumors. and malignantMalignant means "cancerous" and is used to describe tumors or neoplasms that grow invasively and have the ability to metastasize. Malignant tumors can cause serious health problems in dogs and cats. tumors, which is crucial for determining appropriate treatment strategies.

Regarding therapy, new approaches to treating heart muscle tumors in dogs are being explored. Traditional treatments involve surgical procedures, which are often risky due to the location of the tumors. Therefore, less invasiveInvasive describes medical procedures or pathogens that enter the body or penetrate tissue. In medicine, invasive procedures can range from minimally invasive techniques to open surgery. and more effective treatment methods are being sought. Research is focusing on chemotherapyChemotherapy refers to the treatment of diseases, especially cancer, with chemical substances or drugs. It aims to kill cancer cells or prevent their growth, but can also affect healthy cells. and targeted therapies that specifically target the molecular properties of tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. cells. These therapies could slow or stop tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. growth without damaging the surrounding healthy tissue.

Another promising area is immunotherapy, which aims to strengthen the dog’s immune systemThe immune system is the body's defense system against infectious agents such as bacteria, viruses, fungi, and parasites. It comprises a complex network of organs, cells, and molecules that work together to protect the body. to fight tumorA tumor is an abnormal growth of tissue that can be benign or malignant. Tumors can develop in any part of the body and affect various functions. cells more effectively. However, these therapeutic approaches are still in an early stage of development, and further studies are needed to assess their efficacy and safety. Overall, research on myocardial tumors in dogs shows that an interdisciplinary approach combining veterinary, genetic, and biotechnological insights is promising for improving the diagnosisA diagnosis is the identification of a disease or condition by its symptoms and/or results from diagnostic tests. It is the first step in the management and treatment of patients. and treatment of this disease.

Frequently asked questions (FAQs)

What are myocardial tumors?

Myocardial tumors are abnormal growths in the heart muscle tissue of dogs. They can be benign or malignant and are often difficult to diagnose, as the symptoms can be nonspecific and only become noticeable in advanced stages. -

What symptoms occur in dogs with myocardial tumors?

Symptoms can vary but often include shortness of breath, cough, reduced performance, weakness, and in severe cases, collapse. Since the heart is affected, cardiac arrhythmias and heart failure may also occur. -

How are myocardial tumors diagnosed in dogs?

Diagnosis is usually made through imaging procedures such as X-ray, ultrasound, or MRI. These methods help locate tumors in the heart muscle and determine their size and position. A biopsy may also be required to confirm the type of tumor. -

What treatment options are available for myocardial tumors in dogs?

Treatment options depend on the type and progression of the tumor. Options include surgical removal, chemotherapy, and radiation therapy. In some cases, palliative treatment to relieve symptoms may be appropriate. -

Can myocardial tumors in dogs be cured?

The chances of cure depend on the type of tumor and its spread. Benign tumors can often be surgically removed, while malignant tumors are more difficult to treat and have a less favorable prognosis. -

Which dog breeds are most commonly affected by myocardial tumors?

Certain breeds, such as Boxers, German Shepherds, and Golden Retrievers, appear to have a higher risk of developing heart muscle tumors. This can be attributed to genetic factors. -

How can the risk of myocardial tumors in dogs be reduced?

Since the exact causes of myocardial tumors are not fully understood, prevention is difficult. However, regular veterinary examinations can help detect the disease at an earlier stage. -

Are myocardial tumors common in dogs?

Myocardial tumors are relatively rare compared to other heart diseases, but they can have serious health consequences when they occur. Due to their rarity, they are often less known and researched. -

How long can a dog live with a myocardial tumor?

The life expectancy of a dog with a myocardial tumor varies greatly and depends on the tumor type, the progression of the disease, and the effectiveness of treatment. With malignant tumors, the prognosis is often less favorable. -

What advances are there in research on myocardial tumors in dogs?

Research is focusing on genetic analyses, the development of new diagnostic methods, and innovative therapies, including targeted and immunotherapeutic approaches. These advances could significantly improve diagnosis and treatment in the future.