Our last issue covered the foundation of heart health. Today, we’ll dive into some of the most common cardiovascular diseases in dogs, explaining what is happening in the body. We’ll then move on to heart failure, diagnostic testing, and what living with heart disease may look like over time.

If you have friends caring for dogs with heart disease, you are welcome to share this to support their journey.

The mitral valve separates the atrium and ventricle on the left side of the heart. When disease affects this valve, some blood flows backwards when the ventricle contracts instead of only moving forward to the body.

Many dogs with mitral valve disease are not symptomatic at the time of diagnosis. While this can feel alarming to learn, this early stage is often when intervention is most effective at prolonging quality of life without symptoms.

As the disease progresses, more blood flows backwards than forward with each heartbeat. Over time, this may lead to heart failure, which we will explain shortly. Some dogs may experience an acute episode if the cords holding the valve in place rupture due to increased force from backward flow. These dogs typically require supportive veterinary care, and recovery depends on the severity of the injury.

This condition involves changes in the heart muscle itself. In dilated cardiomyopathy (DCM), the heart muscle becomes thinner and weaker. A helpful comparison is a balloon that had been overinflated and can no longer spring back to its original shape.

DCM may affect both the left and right side of the heart, although one side is typically more severely affected. Signs depend on which side is most involved, but commonly include exercise intolerance and lethargy, signs that are unfortunately not very specific.

Dilated cardiomyopathy has been associated with grain-free diets, though research has not yet clarified the cause of this connection. Golden retrievers are overrepresented among dogs that develop DCM while eating grain-free diets, which is an area of ongoing study.

Heart failure occurs when the body is no longer able to compensate for heart disease. In this state, the heart cannot move fluid forward effectively, causing fluid to back up into areas upstream from the failing side of the heart. This backup leads to dysfunction in affected systems.

In left-sided heart failure (mitral valve disease is one example), fluid backs up into the lungs. This often results in labored breathing and distress. Fluid in the lungs interferes with oxygen absorption and can trigger a cascade of additional problems.

In right-sided heart failure, fluid backs up into the body. This may lead to free fluid in the abdomen, stress on organs such as the liver, and swelling of the limbs.

Prognosis depends on the cause of heart failure and which treatment options remain available. Regardless of cause, heart failure is always considered a very serious condition.

Several tests may be used to diagnose and monitor cardiovascular health, in addition to routine screening tests we covered HERE. These commonly include x-rays, echocardiograms, electrocardiogram, and Cardio ProBNP testing.

X-rays (radiographs) are used to assess heart silhouette size and lung health. By comparing the heart to the length of a vertebra, veterinarians can estimate whether heart size is appropriate for an individual dog. Radiograph may also reveal lung changes caused by heart disease.

An echocardiogram (echo) is an ultrasound of the heart. It allows measurement of chamber size, evaluation of blood flow patterns, and assessment of overall heart function. When performed by a cardiologist, this is the ideal test for understanding heart disease and tailoring medication doses.

Echos are time-intensive, and veterinary cardiologists are relatively rare, so this test is not always immediately available. In some cases, treatment by your regular veterinarian may begin before an echo is possible.

An electrocardiogram (EKG) records the electrical activity that keeps the heart in rhythm. In veterinary medicine, EKGs are most commonly used during anesthesia. They may also be used when arrhythmias or fainting episodes are suspected, sometimes with monitoring over an extended period.

One of the newer tools in heart monitoring is the Cardio ProBNP blood test. This test measures levels of a protein associated with heart stress. Currently this test is used to rule disease in rather than out, and may be used for monitoring response to treatment. As this is a newer test, our understanding of how best to use it will continue to evolve with time.

Most heart disease treatments involve medication. While procedures or supportive measures may be used in select cases, long-term management for most dogs relies on medication for life.

Medication may change over time, but once heart function declines enough to require treatment, it is uncommon for dogs to stabilize enough to discontinue medication entirely. The good news is that most heart medications are well tolerated, and side effects are often mild or uncommon. Your veterinarian may monitor bloodwork to ensure supporting the heart is not placing excess strain on other organs.

Short answer: usually, yes. Many dogs with heart disease undergo anesthesia safely. Cardiologist evaluation and recommendations are extremely helpful in assessing relative risk and guiding anesthetic management.

Very rarely, cardiologists may advise against non-life-saving procedures or recommend anesthesia be performed under a boarded anesthesiologist. As with everything in medicine, no option is without risk. However, when heart health is evaluated and the reason for anesthesia is appropriate, procedures may still be recommended.

Life expectancy varies widely and depends on the specific heart disease, severity, and overall health. Many dogs live comfortably with heart disease for years and ultimately pass from unrelated causes. Others may decline more rapidly based on the nature of their disease.

Often, these outcomes follow predictable patterns. In cases of rapid decline, there is usually a strong suspicion ahead of time that is the path forward. While we have limited control over what diseases our dogs develop, we have significant control over how we support them. An informed, attentive pet parent remains one of the most powerful tools in caring for a dog with chronic disease.