What is heart failure?
Heart failure is the inability of the heart muscle to pump effectively. The most common causes of heart failure are the progression of chronic valve disease (degeneration) or heart muscle disease (cardiomyopathy); in rare cases, congenital or diet-related heart conditions may also result in heart failure.
Routine wellness exams are an excellent way to know if your pet has a heart murmur (or develops one with age). From there, a veterinarian may recommend diagnostic and treatment steps that can help prevent an emergency and prolong the course of the disease.
Signs and symptoms of heart failure.
The signs of forward heart failure result when the heart cannot generate enough pressure to send blood to the body. These signs include:
- Lethargy
- Fainting
- Exercise intolerance
- Dullness
- Cold extremities (ears, toes, oral mucosa, rectal temperature)
- Pale gums
- Low blood pressure
Signs of congestive heart failure involve the build-up of fluid in the lungs, the chest and/or the abdomen. This can then result in:
- Coughing
- Increased rate or effort of breathing
- Shallow breathing/increased panting
- Open-mouthed breathing (especially in cats, who do not normally pant)
- Inability to lay down or rest
- Distention of the abdomen
- Moist airway sounds
- Blue tinge to the gums (cyanosis)
Because normal heart function is important for providing circulation to all organs, systemic signs such as vomiting, diarrhea, inappetence and lab work changes consistent with decreased perfusion to the kidneys and liver are all possible with heart failure.
Causes.
In small and medium-sized dogs, long-standing mitral valve disease (mitral valve degeneration or MVD) is the most common cause of heart failure. This is typically first identified as a heart murmur that increases in intensity over time. As the heart grows in size, it can also put pressure on the lower airways – the mainstem bronchi and trachea. This pressure, combined with a build-up of fluid in the lungs from the heart failure itself, can cause coughing and breathing problems.
In large breed dogs, a thinning out and dilation of the heart (dilated cardiomyopathy, or DCM) is also an important cause of heart failure, and this can result in both forward and backward signs. Breeds such as boxers and Doberman pinschers may present with this disorder, which has a genetic component. Enlargement of the heart, a heart murmur, and sometimes associated arrhythmias can exist simultaneously. Fluid accumulation in the lungs as well as sometimes the abdomen and/or chest can be present in these patients.
In cats, heart muscle conditions (cardiomyopathies) are the most common cause of heart failure, with HCM (hypertrophic cardiomyopathy that results in thickening of the heart muscle) making up the majority. Purebred cats such as Maine coons and Norwegian Forest cats are over-represented; however, plenty of mixed breed or domestic shorthaired cats also have heart disease.
Recently, grain-free, legume-rich, boutique diets have been shown to cause a specific diet-associated dilated cardiomyopathy, which has unfortunately resulted in heart failure in a number of dogs. Cardiologists and nutritionists at several veterinary schools have documented the existence of this disease, and the FDA has joined the scientific community in investigating this growing problem.
Lastly, like people, all animals can have congenital heart malformations that can also progress to heart failure if undiagnosed or untreated. Fortunately, interventional and surgical procedures are available to correct some congenital heart conditions in dogs and cats.
Getting a diagnosis.
For patients in overt heart failure, diagnostic tests must be performed with care and patience since their cardio-respiratory status is unstable, and additional stress can cause rapid decline and even death. Often the patient must be stabilized to some degree before tests can be performed. Such tests include:
- Point of care ultrasound (POCUS) of the chest/abdomen may be performed with minimal distress as soon as a patient is triaged. This can show the presence of free fluid (in the chest, abdomen or pericardium) or pulmonary edema (fluid in the lungs). Depending on the ultrasound operator’s experience, some idea about heart chamber size and contractility may also be obtained.
- Chest radiographs (x-rays) are an excellent tool to evaluate heart size, the presence of fluid in the chest and pulmonary edema. These may require that the patient be sedated, gently restrained or both in order to obtain the images. For this reason, radiographs are sometimes postponed until the patient is more stable.
- Complete echocardiography performed by a specialist in cardiology (or in an associated specialty and who is well-versed in echocardiography) is the gold standard test to determine chamber size, valve competency and heart function. This test should be performed as soon as is reasonable, though it may not be available on an emergency basis.
- Blood pressure to provide information on cardiac output.
- Electrocardiography to provide information on heart rhythm and rate.
- Pulse oximetry may provide information on the oxygenation status of the blood; however, this test should be used in combination with clinical signs to guide therapy.
- Baseline lab work to provide electrolyte and kidney enzyme values at minimum since they can be affected by treatment for heart failure.
- Occasionally, the use of cardiac enzyme blood tests (ProBNP and troponins) if needed to further characterize the disease.
- In some geographic locations, testing for infectious diseases (such as Chagas disease) may be discussed.
Questions for your doctor.
When consulting with your pet’s veterinarian, consider asking questions like:
- How advanced is my pet’s heart disease?
- How can I monitor for progression and prevent the need for hospitalization?
- What medications can help prolong the progression of disease?
- Can you provide me with a referral to a cardiologist?
Treatment.
Patients in heart failure are often unstable and require emergent care and hospitalization. Many first-time heart failure patients can show a dramatic response to treatment and may be able to go home within 12-24 hours. Patients with mild or early signs may even be treated as an outpatient.
Patients with a more advanced stage of disease or those who have already been on heart medications for some time may require more complex drug adjustments and longer hospitalization.
The goals of treatment are to relieve respiratory distress and support heart function. This is accomplished by using:
- Oxygen (usually with a cage or nasal prongs)
- Medications to help clear fluid build-up in the lungs (diuretics)
- Mild opioid sedatives to decrease anxiety and dyspnea (labored breathing)
- Medications to improve heart contractility
- Medications to reduce afterload
- Medications to reduce water retention
- Occasionally in cats, the use of anti-platelet medications to prevent clot formation
- Removal of fluid from the chest, pericardium or abdomen
- Mild dietary modifications in advanced stages of disease
- Medications to alleviate cough symptoms
- Medications to help arrhythmias, if indicated
Prevention.
One of the most important choices we can make for our pets is feeding them high-quality mainstream brand foods (Royal Canin, Hill’s Science Diet or Purina, for example) that are balanced in all the ingredients necessary to maintain heart health.
Preventative care in the form of annual wellness exams and breed screening as recommended by your veterinarian are also excellent ways to detect heart disease before it progresses to heart failure.
Prognosis.
It is important to understand that heart failure is a complication of heart disease, which is progressive and eventually terminal. Each hospitalization for heart failure tends to result in smaller gains and shorter out-of-hospital periods.
A combination of several medications given at least twice daily will be needed life-long once a patient has been in heart failure. Patients with heart disease not yet in heart failure may also benefit from medical treatment to prolong the onset of heart failure.
Depending on the stage of disease at the time of diagnosis and response to treatment, pets may have from several weeks or months to a year or more of quality of life.
