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Myocardial Tumors (Heart Muscle Tumors) in Dogs

Occurrence: very rare
Location of illness: Chest

Author: Dr. med. vet. Gisa Löwe | Last modified: 06.11.2025

Myocardial tumors, also known as 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 their effects on heart function.

The most important facts at a glance

Myocardial tumors in dogs are rare but serious conditions that affect the heart muscle. These tumors can originate primarily in the heart or reach it secondarily through metastasisA 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, but 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. inflammatory conditions play a role. Symptoms include cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems., cough, reduced exercise tolerance, and in severe cases, respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress 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 techniques 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-rays, 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. 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 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. removal 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 unknown. 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 non-invasive 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 presence 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 do occur, they can have significant health implications. Science distinguishes between 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 less common, while secondary tumors are more common because they can affect the heart as part of a metastatic process.

The exact causes of myocardial tumors in dogs are not yet fully understood. Genetic factors are believed to play a role, especially in certain dog breeds that are more prone 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 lie in 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. inflammatory conditions of the heart tissue. Long-term inflammation can lead to cell 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 link 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 respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress, cough, lethargy, and decreased exercise tolerance. These symptoms result from the impaired pumping capacity of the heart, which leads to an inadequate supply of oxygen to the body. Some dogs may also experience fainting spells or weakness, especially after physical exertion.

In advanced cases, fluid may accumulate in the abdominalThe term “abdominal” refers to anything that concerns the belly or the abdomen. It is an adjectival expression used to describe the location, symptoms, or conditions that occur in the abdominal area. cavity (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 in the chest cavity (pleural effusion), 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 cardiovascular 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 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 may 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.. An echocardiogram (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. of the heart) can help assess the structure and function of the heart and identify tumors in the heart muscle. Chest X-rays 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 cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems. 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 necessary 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 with 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 dog’s general health. Treatment 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..

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 because the heart is a delicate organ and the surgery itself can be life-threatening. In many cases, complete removal of the tumor 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 down 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 therapy.

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. may be used in some cases, especially 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. 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 can 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 metastasize. 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. However, in some dogs, early detection and treatment can prolong life and alleviate symptoms.

Prevention

Since the exact causes of myocardial tumors are not fully known, there are no specific preventive measures. However, general health care and regular veterinary check-ups can help detect and treat health problems early.

A balanced diet, regular exercise, and avoidance of environmental toxins can contribute to the dog’s general health and potentially 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 the veterinarian may be useful in order to intervene early.

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 in order to develop earlier diagnostic methods and more effective treatment strategies. One of the main directions is the study of genetic abnormalities that can promote the growth of tumors in the heart muscle. It is believed that certain genetic mutations in dogs may 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 non-invasive diagnostic tools. Currently, imaging techniques 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 make it possible to make a 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.

With regard 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., new approaches to the treatment of heart muscle tumors in dogs are being explored. Traditional treatments involve surgical interventions, 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 down 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 that combines veterinary, genetic, and biotechnological knowledge is promising in order to improve 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 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 are often difficult to diagnose because the symptoms can be non-specific and only become noticeable in advanced stages.
What symptoms occur in dogs with myocardial tumors? The symptoms can vary, but often include respiratoryRespiratory refers to breathing or the process of breathing. Respiratory diseases affect the respiratory tract and can impair the ability to breathe effectively. distress, cough, reduced performance, weakness, and in severe cases, collapse. Since the heart is affected, cardiac arrhythmiaAn arrhythmia is a heart rhythm disorder in which the heart beats irregularly, either too fast (tachycardia), too slow (bradycardia), or with an irregular pattern. Arrhythmias can be harmless or a sign of serious heart problems. and heart failure can also occur.
How are myocardial tumors diagnosed in dogs? 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. is usually made by imaging techniques such as X-ray, ultrasound, or MRI. These methods help to locate tumors in the heart muscle and determine their size and position. 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. may also be necessary to confirm 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..
What treatment options are available for myocardial tumors in dogs? Treatment options depend on the type and progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. 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.. Options include surgical removal, 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.. In some cases, palliativePalliative refers to treatments that aim to alleviate the symptoms of a disease without curing the disease itself. Palliative care focuses on improving the quality of life of patients with incurable diseases. treatment to relieve symptoms may be useful.
Can myocardial tumors be cured in dogs? The chances of a cure 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 its spread. 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 can often be surgically removed, while 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 are more difficult to treat and have a less favorable 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..
Which dog breeds are most commonly affected by myocardial tumors? Certain breeds, such as Boxers, German Shepherds, and Golden Retrievers, appear to be at higher risk of developing heart muscle tumors. This may be due to genetic factors.
How can the risk of myocardial tumors be reduced in dogs? Since the exact causes of myocardial tumors are not fully understood, preventionPrevention includes measures taken to prevent diseases or injuries. In veterinary medicine, this includes vaccinations, parasite control, and health monitoring. is difficult. However, a regular veterinary examination can help to 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 if they occur. Due to their rarity, they are often less well known and researched.
How long can a dog with a myocardial 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. live? The life expectancy of a dog with a myocardial 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. varies greatly and 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, the progressionProgression refers to the advancement or worsening of a disease over time. It describes an increase in the severity or extent of the disease symptoms. of the disease, and the effectiveness of the treatment. 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. is often less favorable for 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.
What advances are being made 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 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 in the future.