A heart tumor in dogs is an abnormal growth on or within the heart, most commonly hemangiosarcoma, a malignant cancer of the blood vessel lining. These tumors often develop silently, with few warning signs until a serious complication occurs. Early detection is difficult but possible with close monitoring of subtle changes in breathing, energy levels, and heart rate.<\/p>\n\n\n\n
\n\n\n\n
Key Takeaways<\/strong><\/h2>\n\n\n\n\n- Hemangiosarcoma is the most common malignant heart tumor in dogs and often progresses without obvious symptoms.<\/li>\n\n\n\n
- Symptoms can appear suddenly and may include weakness, labored breathing, and collapse.<\/li>\n\n\n\n
- Diagnosis requires imaging such as echocardiography (heart ultrasound).<\/li>\n\n\n\n
- Prognosis is generally poor, but supportive care and monitoring can meaningfully improve quality of life.<\/li>\n\n\n\n
- Tracking resting respiratory rate, heart rate, and activity patterns at home can help identify changes earlier.<\/li>\n<\/ul>\n\n\n\n
\n\n\n\nWhat Is a Heart Tumor in Dogs?<\/strong><\/h2>\n\n\n\n![\"\"](\"https:\/\/maven.pet\/all-about-pets\/wp-content\/uploads\/2026\/02\/heart_tumors_in_dogs_what_is.jpg\")
<\/figure>\n\n\n\nA heart tumor, also called a cardiac tumor, is an abnormal mass that forms on or inside the heart. According to VCA Animal Hospitals<\/a>, these tumors can be primary<\/strong> (originating in the heart itself) or secondary<\/strong> (metastasized from cancer elsewhere in the body).<\/p>\n\n\n\nPrimary cardiac tumors are uncommon in dogs, but when they do occur, they tend to be aggressive. The heart’s constant motion and rich blood supply make surgical treatment extremely challenging, which is why monitoring and early detection are so important.<\/p>\n\n\n\n
As noted by Cornell University College of Veterinary Medicine<\/a>, certain breeds are at higher risk, including Golden Retrievers, German Shepherds, and Labrador Retrievers<\/strong>. Middle-aged to senior dogs are most commonly affected.<\/p>\n\n\n\n
\n\n\n\nHemangiosarcoma in Dogs’ Hearts: What Owners Should Know<\/strong><\/h2>\n\n\n\nHemangiosarcoma (HSA) is the most common malignant heart tumor in dogs, accounting for the majority of primary cardiac tumors, according to Cornell University College of Veterinary Medicine<\/a>. It originates in the cells lining the blood vessels and most often develops in the right atrium<\/strong>, the chamber of the heart responsible for receiving blood from the body, as described by the AVMA<\/a>.<\/p>\n\n\n\nBecause hemangiosarcoma grows within the heart wall, it can rupture and bleed into the pericardium (the sac surrounding the heart), causing a life-threatening condition called pericardial effusion<\/strong>. VCA Animal Hospitals<\/a> explains that this fluid build-up compresses the heart, preventing it from pumping effectively. Many dogs are first diagnosed after collapsing due to this complication.<\/p>\n\n\n\nThe second most common primary cardiac tumor is chemodectoma<\/strong>, which develops near the base of the heart and tends to grow more slowly than hemangiosarcoma, as outlined by VCA Animal Hospitals<\/a>.<\/p>\n\n\n\n“Heart tumors can be difficult to detect early because symptoms often appear suddenly. Monitoring changes in breathing, energy, and behavior can help identify issues sooner.”<\/em> Carolina Domingues, DVM, Veterinarian at Maven Pet<\/strong><\/p>\n\n\n\n<\/span>\n\u201cI got the Maven sensor for my 14-year-old Chihuahua mix with heart and trachea issues. It gave me back peace of mind <\/strong>– I can track her RRR, BPM, drinking, and activity anytime and know instantly if something\u2019s wrong. Highly recommend!\u201d <\/em><\/p>\n\n\n\n\n\n![\"\"](\"https:\/\/maven.pet\/all-about-pets\/wp-content\/uploads\/2025\/09\/Chiara-De-Luca-Titti.jpg\")
<\/figure>\n<\/div><\/div>\n\n\n\n\n\n\u2605\u2605\u2605\u2605\u2605<\/p>\n\n\n\n
Chiara De Luca
Titti<\/strong><\/p>\n\n\n\n<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
\nTrack your dog’s health!<\/strong><\/a><\/div>\n<\/div>\n<\/div><\/div>\n\n\n\n
\n\n\n\nWhat Are the Symptoms of a Heart Tumor in Dogs?<\/strong><\/h2>\n\n\n\nBecause heart tumors often grow silently, Cornell University College of Veterinary Medicine<\/a> notes that symptoms can appear suddenly, sometimes without any prior warning signs. Watch closely for:<\/p>\n\n\n\n\n- Sudden weakness or collapse<\/strong> (often the first visible sign)<\/li>\n\n\n\n
- Labored or rapid breathing<\/strong>, even at rest<\/li>\n\n\n\n
- Reduced exercise tolerance<\/strong>, tiring quickly on walks or play<\/li>\n\n\n\n
- Distended abdomen<\/strong> from fluid accumulation<\/li>\n\n\n\n
- Pale or bluish gums<\/strong><\/li>\n\n\n\n
- Irregular heartbeat or heart murmur<\/strong> (detected by a vet)<\/li>\n\n\n\n
- Decreased appetite and unexplained weight loss<\/strong><\/li>\n\n\n\n
- Restlessness or difficulty getting comfortable<\/strong><\/li>\n<\/ul>\n\n\n\n
If your dog shows any of these signs, contact your veterinarian immediately. Sudden collapse or difficulty breathing is a veterinary emergency.<\/p>\n\n\n\n
\n\n\n\nHow Are Heart Tumors Diagnosed?<\/strong><\/h2>\n\n\n\nDiagnosing a heart tumor typically involves several steps, as outlined by Cornell University College of Veterinary Medicine<\/a> and the Texas A&M Veterinary Medical Teaching Hospital<\/a>:<\/p>\n\n\n\n\n- Physical examination<\/strong>: Your vet listens for abnormal heart sounds or a muffled heartbeat, which can suggest fluid around the heart.<\/li>\n\n\n\n
- Chest X-rays<\/strong>: Can reveal an enlarged cardiac silhouette caused by pericardial effusion.<\/li>\n\n\n\n
- Echocardiography (heart ultrasound)<\/strong>: The gold standard for identifying cardiac masses. It allows the vet to visualize the tumor’s location, size, and effect on heart function.<\/li>\n\n\n\n
- Electrocardiogram (ECG)<\/strong>: Detects arrhythmias that are common with cardiac tumors.<\/li>\n\n\n\n
- Blood work and biomarkers<\/strong>: General health panels assess overall organ function; some markers may suggest active bleeding or cancer burden.<\/li>\n<\/ol>\n\n\n\n
As the AVMA<\/a> highlights, definitive diagnosis usually requires imaging, as biopsies of the heart carry significant risk.<\/p>\n\n\n\n
\n\n\n\nWhat Are the Treatment Options and Prognosis?<\/strong><\/h2>\n\n\n\n![\"\"](\"https:\/\/maven.pet\/all-about-pets\/wp-content\/uploads\/2026\/02\/heart_tumors_in_dogs_treatment.jpg\")
<\/figure>\n\n\n\nTreatment depends on the tumor type, size, and the dog’s overall health. VCA Animal Hospitals<\/a> and the Texas A&M Veterinary Medical Teaching Hospital<\/a> outline the main options:<\/p>\n\n\n\n\n- Pericardiocentesis<\/strong>: Emergency drainage of fluid from the pericardial sac to relieve pressure and stabilize the dog.<\/li>\n\n\n\n
- Surgery (pericardiectomy)<\/strong>: Removal of part of the pericardium to prevent fluid re-accumulation. This can provide meaningful relief but does not remove the tumor.<\/li>\n\n\n\n
- Chemotherapy<\/strong>: May extend survival time in dogs with hemangiosarcoma, though responses vary.<\/li>\n\n\n\n
- Palliative care<\/strong>: Focuses on comfort, quality of life, and managing symptoms.<\/li>\n<\/ul>\n\n\n\n
Prognosis for cardiac hemangiosarcoma is unfortunately guarded to poor. Cornell University College of Veterinary Medicine<\/a> reports that median survival time with surgery and chemotherapy is typically 4 to 6 months, though some dogs do better. According to VCA Animal Hospitals<\/a>, chemodectomas tend to carry a somewhat longer prognosis. Every dog is different, and your veterinarian is the best person to discuss realistic expectations for your specific situation.<\/p>\n\n\n\n
\n\n\n\nWhat to Expect as the Disease Progresses<\/strong><\/h2>\n\n\n\nHeart tumors, especially hemangiosarcoma, can progress unpredictably. Periods of relative stability may be interrupted by sudden deterioration. VCA Animal Hospitals<\/a> notes that common developments include repeated pericardial effusion requiring drainage, increasing fatigue and reduced mobility, and eventually the decision around quality of life and end-of-life care.<\/p>\n\n\n\nBeing attuned to your dog’s daily rhythms, including energy, breathing, appetite, and rest, becomes especially important during this time.<\/p>\n\n\n\n
\n\n\n\nHow Maven Helps Monitor Subtle Changes<\/strong><\/h2>\n\n\n\nOne of the greatest challenges with dog heart disease is that meaningful changes can occur between vet visits, often going unnoticed until they become urgent.<\/p>\n\n\n\n
The Maven Pet Health Monitor<\/strong> continuously tracks your dog’s resting respiratory rate, heart rate, activity levels, rest patterns, and water intake, building a personalized baseline unique to your dog. For dogs with heart tumors, rising resting respiratory rate or declining activity can be early indicators of fluid accumulation or cardiac stress, often before visible distress appears.<\/p>\n\n\n\n![\"\"](\"https:\/\/maven.pet\/all-about-pets\/wp-content\/uploads\/2025\/09\/prod-dog.jpg\")
<\/span>\n\n\n![\"\"](\"https:\/\/maven.pet\/all-about-pets\/wp-content\/uploads\/2025\/09\/dog-scr.png\")
<\/figure>\n<\/div>\n\n\n\n\n\nMonitor heart rate, respiratory rate, activity & rest, drinking, itch behavior.<\/strong><\/p>\n<\/div><\/div>\n\n\n\n\n
\n\n\n\n
What Is a Heart Tumor in Dogs?<\/strong><\/h2>\n\n\n\n<\/figure>\n\n\n\nA heart tumor, also called a cardiac tumor, is an abnormal mass that forms on or inside the heart. According to VCA Animal Hospitals<\/a>, these tumors can be primary<\/strong> (originating in the heart itself) or secondary<\/strong> (metastasized from cancer elsewhere in the body).<\/p>\n\n\n\nPrimary cardiac tumors are uncommon in dogs, but when they do occur, they tend to be aggressive. The heart’s constant motion and rich blood supply make surgical treatment extremely challenging, which is why monitoring and early detection are so important.<\/p>\n\n\n\n
As noted by Cornell University College of Veterinary Medicine<\/a>, certain breeds are at higher risk, including Golden Retrievers, German Shepherds, and Labrador Retrievers<\/strong>. Middle-aged to senior dogs are most commonly affected.<\/p>\n\n\n\n
\n\n\n\nHemangiosarcoma in Dogs’ Hearts: What Owners Should Know<\/strong><\/h2>\n\n\n\nHemangiosarcoma (HSA) is the most common malignant heart tumor in dogs, accounting for the majority of primary cardiac tumors, according to Cornell University College of Veterinary Medicine<\/a>. It originates in the cells lining the blood vessels and most often develops in the right atrium<\/strong>, the chamber of the heart responsible for receiving blood from the body, as described by the AVMA<\/a>.<\/p>\n\n\n\nBecause hemangiosarcoma grows within the heart wall, it can rupture and bleed into the pericardium (the sac surrounding the heart), causing a life-threatening condition called pericardial effusion<\/strong>. VCA Animal Hospitals<\/a> explains that this fluid build-up compresses the heart, preventing it from pumping effectively. Many dogs are first diagnosed after collapsing due to this complication.<\/p>\n\n\n\nThe second most common primary cardiac tumor is chemodectoma<\/strong>, which develops near the base of the heart and tends to grow more slowly than hemangiosarcoma, as outlined by VCA Animal Hospitals<\/a>.<\/p>\n\n\n\n“Heart tumors can be difficult to detect early because symptoms often appear suddenly. Monitoring changes in breathing, energy, and behavior can help identify issues sooner.”<\/em> Carolina Domingues, DVM, Veterinarian at Maven Pet<\/strong><\/p>\n\n\n\n<\/span>\n\u201cI got the Maven sensor for my 14-year-old Chihuahua mix with heart and trachea issues. It gave me back peace of mind <\/strong>– I can track her RRR, BPM, drinking, and activity anytime and know instantly if something\u2019s wrong. Highly recommend!\u201d <\/em><\/p>\n\n\n\n\n\n<\/figure>\n<\/div><\/div>\n\n\n\n\n\n\u2605\u2605\u2605\u2605\u2605<\/p>\n\n\n\n
Chiara De Luca
Titti<\/strong><\/p>\n\n\n\n<\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n
\nTrack your dog’s health!<\/strong><\/a><\/div>\n<\/div>\n<\/div><\/div>\n\n\n\n
\n\n\n\nWhat Are the Symptoms of a Heart Tumor in Dogs?<\/strong><\/h2>\n\n\n\nBecause heart tumors often grow silently, Cornell University College of Veterinary Medicine<\/a> notes that symptoms can appear suddenly, sometimes without any prior warning signs. Watch closely for:<\/p>\n\n\n\n\n- Sudden weakness or collapse<\/strong> (often the first visible sign)<\/li>\n\n\n\n
- Labored or rapid breathing<\/strong>, even at rest<\/li>\n\n\n\n
- Reduced exercise tolerance<\/strong>, tiring quickly on walks or play<\/li>\n\n\n\n
- Distended abdomen<\/strong> from fluid accumulation<\/li>\n\n\n\n
- Pale or bluish gums<\/strong><\/li>\n\n\n\n
- Irregular heartbeat or heart murmur<\/strong> (detected by a vet)<\/li>\n\n\n\n
- Decreased appetite and unexplained weight loss<\/strong><\/li>\n\n\n\n
- Restlessness or difficulty getting comfortable<\/strong><\/li>\n<\/ul>\n\n\n\n
If your dog shows any of these signs, contact your veterinarian immediately. Sudden collapse or difficulty breathing is a veterinary emergency.<\/p>\n\n\n\n
\n\n\n\nHow Are Heart Tumors Diagnosed?<\/strong><\/h2>\n\n\n\nDiagnosing a heart tumor typically involves several steps, as outlined by Cornell University College of Veterinary Medicine<\/a> and the Texas A&M Veterinary Medical Teaching Hospital<\/a>:<\/p>\n\n\n\n\n- Physical examination<\/strong>: Your vet listens for abnormal heart sounds or a muffled heartbeat, which can suggest fluid around the heart.<\/li>\n\n\n\n
- Chest X-rays<\/strong>: Can reveal an enlarged cardiac silhouette caused by pericardial effusion.<\/li>\n\n\n\n
- Echocardiography (heart ultrasound)<\/strong>: The gold standard for identifying cardiac masses. It allows the vet to visualize the tumor’s location, size, and effect on heart function.<\/li>\n\n\n\n
- Electrocardiogram (ECG)<\/strong>: Detects arrhythmias that are common with cardiac tumors.<\/li>\n\n\n\n
- Blood work and biomarkers<\/strong>: General health panels assess overall organ function; some markers may suggest active bleeding or cancer burden.<\/li>\n<\/ol>\n\n\n\n
As the AVMA<\/a> highlights, definitive diagnosis usually requires imaging, as biopsies of the heart carry significant risk.<\/p>\n\n\n\n
\n\n\n\nWhat Are the Treatment Options and Prognosis?<\/strong><\/h2>\n\n\n\n<\/figure>\n\n\n\nTreatment depends on the tumor type, size, and the dog’s overall health. VCA Animal Hospitals<\/a> and the Texas A&M Veterinary Medical Teaching Hospital<\/a> outline the main options:<\/p>\n\n\n\n\n- Pericardiocentesis<\/strong>: Emergency drainage of fluid from the pericardial sac to relieve pressure and stabilize the dog.<\/li>\n\n\n\n
- Surgery (pericardiectomy)<\/strong>: Removal of part of the pericardium to prevent fluid re-accumulation. This can provide meaningful relief but does not remove the tumor.<\/li>\n\n\n\n
- Chemotherapy<\/strong>: May extend survival time in dogs with hemangiosarcoma, though responses vary.<\/li>\n\n\n\n
- Palliative care<\/strong>: Focuses on comfort, quality of life, and managing symptoms.<\/li>\n<\/ul>\n\n\n\n
Prognosis for cardiac hemangiosarcoma is unfortunately guarded to poor. Cornell University College of Veterinary Medicine<\/a> reports that median survival time with surgery and chemotherapy is typically 4 to 6 months, though some dogs do better. According to VCA Animal Hospitals<\/a>, chemodectomas tend to carry a somewhat longer prognosis. Every dog is different, and your veterinarian is the best person to discuss realistic expectations for your specific situation.<\/p>\n\n\n\n
\n\n\n\nWhat to Expect as the Disease Progresses<\/strong><\/h2>\n\n\n\nHeart tumors, especially hemangiosarcoma, can progress unpredictably. Periods of relative stability may be interrupted by sudden deterioration. VCA Animal Hospitals<\/a> notes that common developments include repeated pericardial effusion requiring drainage, increasing fatigue and reduced mobility, and eventually the decision around quality of life and end-of-life care.<\/p>\n\n\n\nBeing attuned to your dog’s daily rhythms, including energy, breathing, appetite, and rest, becomes especially important during this time.<\/p>\n\n\n\n
\n\n\n\nHow Maven Helps Monitor Subtle Changes<\/strong><\/h2>\n\n\n\nOne of the greatest challenges with dog heart disease is that meaningful changes can occur between vet visits, often going unnoticed until they become urgent.<\/p>\n\n\n\n
The Maven Pet Health Monitor<\/strong> continuously tracks your dog’s resting respiratory rate, heart rate, activity levels, rest patterns, and water intake, building a personalized baseline unique to your dog. For dogs with heart tumors, rising resting respiratory rate or declining activity can be early indicators of fluid accumulation or cardiac stress, often before visible distress appears.<\/p>\n\n\n\n<\/span>\n\n\n<\/figure>\n<\/div>\n\n\n\n\n\nMonitor heart rate, respiratory rate, activity & rest, drinking, itch behavior.<\/strong><\/p>\n<\/div><\/div>\n\n\n\n\n
<\/figure>\n\n\n\nA heart tumor, also called a cardiac tumor, is an abnormal mass that forms on or inside the heart. According to VCA Animal Hospitals<\/a>, these tumors can be primary<\/strong> (originating in the heart itself) or secondary<\/strong> (metastasized from cancer elsewhere in the body).<\/p>\n\n\n\n Primary cardiac tumors are uncommon in dogs, but when they do occur, they tend to be aggressive. The heart’s constant motion and rich blood supply make surgical treatment extremely challenging, which is why monitoring and early detection are so important.<\/p>\n\n\n\n As noted by Cornell University College of Veterinary Medicine<\/a>, certain breeds are at higher risk, including Golden Retrievers, German Shepherds, and Labrador Retrievers<\/strong>. Middle-aged to senior dogs are most commonly affected.<\/p>\n\n\n\n Hemangiosarcoma (HSA) is the most common malignant heart tumor in dogs, accounting for the majority of primary cardiac tumors, according to Cornell University College of Veterinary Medicine<\/a>. It originates in the cells lining the blood vessels and most often develops in the right atrium<\/strong>, the chamber of the heart responsible for receiving blood from the body, as described by the AVMA<\/a>.<\/p>\n\n\n\n Because hemangiosarcoma grows within the heart wall, it can rupture and bleed into the pericardium (the sac surrounding the heart), causing a life-threatening condition called pericardial effusion<\/strong>. VCA Animal Hospitals<\/a> explains that this fluid build-up compresses the heart, preventing it from pumping effectively. Many dogs are first diagnosed after collapsing due to this complication.<\/p>\n\n\n\n The second most common primary cardiac tumor is chemodectoma<\/strong>, which develops near the base of the heart and tends to grow more slowly than hemangiosarcoma, as outlined by VCA Animal Hospitals<\/a>.<\/p>\n\n\n\n “Heart tumors can be difficult to detect early because symptoms often appear suddenly. Monitoring changes in breathing, energy, and behavior can help identify issues sooner.”<\/em> Carolina Domingues, DVM, Veterinarian at Maven Pet<\/strong><\/p>\n\n\n\n \u201cI got the Maven sensor for my 14-year-old Chihuahua mix with heart and trachea issues. It gave me back peace of mind <\/strong>– I can track her RRR, BPM, drinking, and activity anytime and know instantly if something\u2019s wrong. Highly recommend!\u201d <\/em><\/p>\n\n\n\n \u2605\u2605\u2605\u2605\u2605<\/p>\n\n\n\n Chiara De Luca <\/p>\n<\/div>\n<\/div>\n<\/div>\n\n\n\n Because heart tumors often grow silently, Cornell University College of Veterinary Medicine<\/a> notes that symptoms can appear suddenly, sometimes without any prior warning signs. Watch closely for:<\/p>\n\n\n\n If your dog shows any of these signs, contact your veterinarian immediately. Sudden collapse or difficulty breathing is a veterinary emergency.<\/p>\n\n\n\n Diagnosing a heart tumor typically involves several steps, as outlined by Cornell University College of Veterinary Medicine<\/a> and the Texas A&M Veterinary Medical Teaching Hospital<\/a>:<\/p>\n\n\n\n As the AVMA<\/a> highlights, definitive diagnosis usually requires imaging, as biopsies of the heart carry significant risk.<\/p>\n\n\n\n Treatment depends on the tumor type, size, and the dog’s overall health. VCA Animal Hospitals<\/a> and the Texas A&M Veterinary Medical Teaching Hospital<\/a> outline the main options:<\/p>\n\n\n\n Prognosis for cardiac hemangiosarcoma is unfortunately guarded to poor. Cornell University College of Veterinary Medicine<\/a> reports that median survival time with surgery and chemotherapy is typically 4 to 6 months, though some dogs do better. According to VCA Animal Hospitals<\/a>, chemodectomas tend to carry a somewhat longer prognosis. Every dog is different, and your veterinarian is the best person to discuss realistic expectations for your specific situation.<\/p>\n\n\n\n Heart tumors, especially hemangiosarcoma, can progress unpredictably. Periods of relative stability may be interrupted by sudden deterioration. VCA Animal Hospitals<\/a> notes that common developments include repeated pericardial effusion requiring drainage, increasing fatigue and reduced mobility, and eventually the decision around quality of life and end-of-life care.<\/p>\n\n\n\n Being attuned to your dog’s daily rhythms, including energy, breathing, appetite, and rest, becomes especially important during this time.<\/p>\n\n\n\n One of the greatest challenges with dog heart disease is that meaningful changes can occur between vet visits, often going unnoticed until they become urgent.<\/p>\n\n\n\n The Maven Pet Health Monitor<\/strong> continuously tracks your dog’s resting respiratory rate, heart rate, activity levels, rest patterns, and water intake, building a personalized baseline unique to your dog. For dogs with heart tumors, rising resting respiratory rate or declining activity can be early indicators of fluid accumulation or cardiac stress, often before visible distress appears.<\/p>\n\n\n\n Monitor heart rate, respiratory rate, activity & rest, drinking, itch behavior.<\/strong><\/p>\n<\/div><\/div>\n\n\n\n
\n\n\n\nHemangiosarcoma in Dogs’ Hearts: What Owners Should Know<\/strong><\/h2>\n\n\n\n
<\/figure>\n<\/div><\/div>\n\n\n\n
Titti<\/strong><\/p>\n\n\n\n
\n\n\n\nWhat Are the Symptoms of a Heart Tumor in Dogs?<\/strong><\/h2>\n\n\n\n
\n
\n\n\n\nHow Are Heart Tumors Diagnosed?<\/strong><\/h2>\n\n\n\n
\n
\n\n\n\nWhat Are the Treatment Options and Prognosis?<\/strong><\/h2>\n\n\n\n
<\/figure>\n\n\n\n\n
\n\n\n\nWhat to Expect as the Disease Progresses<\/strong><\/h2>\n\n\n\n
\n\n\n\nHow Maven Helps Monitor Subtle Changes<\/strong><\/h2>\n\n\n\n
<\/span><\/figure>\n<\/div>\n\n\n\n