What is congestive heart failure?

Congestive heart failure¹—also referred to simply as heart failure—occurs when the heart muscle doesn’t pump blood as well as it should. Heart failure can be present over a long period of time (chronic) or may start suddenly (acute).

Congestive heart failure often develops after other conditions have damaged or weakened the heart. Conditions like coronary artery disease² (narrowed arteries in the heart) or hypertension³ (high blood pressure) gradually leave the heart too weak or stiff to fill and pump blood efficiently.

However, the heart doesn’t necessarily need to be weakened to cause heart failure—this condition can also occur if the heart becomes too stiff to function properly.

How common is congestive heart failure?

Nearly 5 million Americans⁴ are currently living with congestive heart failure, and approximately 550,000 new cases of CHF are diagnosed in the United States each year.

Congestive heart failure affects people of all ages, from children and young adults to the middle-aged and elderly. The condition is equally frequent in men and women.

The risk of CHF does tend to increase with age, however—congestive heart failure is the most common diagnosis in hospital patients age 65 years and older. While the condition is present in 2% of people ages 40–59, more than 5% of people ages 60–69 have CHF, and the annual incidence of CHF approaches 10 per 1,000 people after 65 years of age.

What about congestive heart failure in dogs?

Dogs can also have congestive heart failure. There are many causes of CHF in dogs⁵. However, the two most common are:

• Mitral valve insufficiency (MVI): MVI is a leaky mitral valve (the valve between the left atrium and left ventricle)
• Dilated cardiomyopathy (DCM): a condition in which the heart’s ability to pump blood is decreased because the heart’s main pumping chamber, the left ventricle, is enlarged and weakened

The most common sign of CHF in dogs is persistent coughing (generally while at rest or sleeping) accompanied by difficulty breathing. These signs are mainly due to pulmonary edema⁶ (the accumulation of fluid in the lungs). An enlarged heart also pushes against the trachea (windpipe), causing irritation that can produce a cough.

Dogs with CHF may also show excessive panting, persistent loss of appetite, a swollen belly, and pale or bluish gums. They will also exhibit weight loss and muscle degeneration due to the effects of CHF on other body systems. Many dogs with congestive heart failure will become tired easily, have reduced stamina, and show decreased engagement in playing or walking.

If any of these signs develop in your pet (especially if he or she has a heart murmur), notify your veterinarian immediately. While heart attacks in dogs are rare, unexpected death in dogs diagnosed with any form of heart disease is possible.

Congestive heart failure in dogs is usually diagnosed using auscultation⁷, chest X-rays, electrocardiogram (ECG), or echocardiogram. An accurate diagnosis allows your vet to provide the best course of treatment necessary. With proper treatment, many dogs with congestive heart failure are able to live a normal life for many months to years.

Congestive heart failure causes

The causes⁸ of heart failure can begin either in the right or left chambers of the heart—or, in some instances, on both sides of the heart. Generally, heart failure begins with the left side—specifically, the left ventricle (the chamber of the heart that pumps blood to the rest of your body).

There are multiple types of heart failure with different symptoms:

• Left-sided heart failure: The left ventricle is unable to contract or relax normally. This, in turn, prevents the left ventricle from filling up between beats and pump blood efficiently to the rest of the body.
• Right-sided heart failure: Fluid may back up into the ventricle that collects “used” blood, causing further back up and swelling in your abdomen, legs, and feet.
• Systolic heart failure: A larger and weaker left ventricle can’t contract vigorously and send blood to the rest of your body.
• Diastolic heart failure (or heart failure with preserved ejection fraction): The left ventricle stiffens and is unable to relax or fill fully with blood, which in turn sends less blood than it should to the rest of your body.
• Dilated cardiomyopathy (DCM): The left ventricle dilates- meaning it stretches and becomes thinner, causing a decrease in the heart’s ability to pump blood to the rest of your body.

When heart failure is present, the main pumping chambers of the heart (ventricles) may become stiff and not fill properly between beats. Heart failure often develops when other conditions have damaged or weakened the heart. Over time, the heart can no longer keep up with the normal demands placed on it to pump blood to the rest of the body.

In some cases, when the heart muscle is damaged or weakened, the ventricles stretch (dilate) to the point where the heart can’t pump blood efficiently throughout the body. The heart can also become stiffened to the point of not being able to properly pump blood through the body.

Any of the following conditions (which can be present without you even knowing it) can damage or weaken the heart, causing heart failure:

• Coronary artery disease and heart attack: Coronary artery disease (CAD) is the most common form of heart disease⁹ and the most common cause of heart failure. The disease is caused by the buildup of fatty deposits (plaque) in the arteries (called atherosclerosis¹⁰), reducing blood flow and potentially leading to a heart attack.

• High blood pressure (hypertension): If you have high blood pressure, your heart has to work harder than it should to circulate blood throughout your body. Over time, this extra exertion can make your heart muscle too stiff or weak to effectively pump blood.
• Faulty heart valves: The valves of your heart keep blood flowing in the proper direction ensuring that it flows in one direction that leads back to the heart. A damaged valve (which may be caused by a heart defect¹¹, coronary artery disease, or a heart infection¹²) forces your heart to work harder, which can weaken it over time.

• Damage to the heart muscle (cardiomyopathy¹³): Damage to the heart muscle can have many causes, including several diseases, infections, alcohol abuse, and the toxic effect of drugs (such as cocaine, or the drugs used for chemotherapy). Genetic factors can also play a role in the development of cardiomyopathy.

• Myocarditis: Myocarditis¹⁴ is an inflammation of the heart muscle. It’s most commonly caused by a virus and can lead to heart failure.

• Congenital heart defects: Congenital heart defects¹⁵ refer to heart defects that you’re born with. If the heart and its chambers or valves haven’t formed properly, the healthy parts of the heart have to work harder to pump blood, which may lead to heart failure.

• Abnormal heart rhythms (heart arrhythmias¹⁶): Abnormal heart rhythms may cause the heart to beat abnormally fast, creating extra work for the muscle. A slow heartbeat may also lead to heart failure.

• Other diseases: Chronic diseases such as diabetes¹⁷, HIV¹⁸, hyper-¹⁹ or hypothyroidism²⁰, or a buildup of iron (hemochromatosis²¹) or protein (amyloidosis²²) may contribute to heart failure. Causes of acute heart failure include viruses that attack the heart muscle, severe infections, allergic reactions, blood clots in the lungs, the use of certain medications, or any illnesses that affect the whole body.

Risk factors for congestive heart failure

Some pre-existing conditions, lifestyle choices, or hereditary factors may contribute to your likelihood of developing congestive heart failure. A single risk factor may be enough to cause heart failure, but a combination of factors further increases your risk.

Some risk factors²³ for congestive heart failure include:

• High blood pressure (hypertension): Your heart works harder than it has to if your blood pressure is high.
• Coronary artery disease: Having narrowed arteries makes it more difficult for blood to flow throughout the body. The heart works harder to compensate and causes the heart muscle to weaken.
• Heart attack: A heart attack is a form of coronary disease that occurs suddenly. Damage to the heart muscle caused by a heart attack may mean that the heart can no longer pump blood as well as it should.
• Diabetes: Having diabetes increases your risk of having high blood pressure and coronary artery disease.
• Sleep apnea: The inability to breathe properly while you sleep results in low blood oxygen levels and increased risk of abnormal heart rhythms—both of which can weaken the heart.
• Congenital heart defects: Some people who develop heart failure were born with structural heart defects.
• Valvular heart disease: People with valvular heart disease²⁴ have a higher risk of heart failure.
• Viruses: A viral infection may damage your heart muscle.
• Alcohol use: Drinking too much alcohol can weaken the heart muscle and lead to heart failure.
• Tobacco use: Using tobacco can increase your risk of heart failure.
• Obesity: People who are obese have a higher risk of developing heart failure.
• Irregular heartbeats: Abnormal heart rhythms—especially if they are very frequent and fast—can weaken the heart muscle and cause heart failure.

Congestive heart failure complications

Congestive heart failure can lead to a number of complications²⁵, including:

• Kidney damage or failure: Heart failure can reduce the flow of blood to your kidneys, which can eventually cause kidney failure²⁶ if left untreated. Kidney damage from heart failure can require treatment with dialysis²⁷.
• Heart valve problems: The valves of your heart keep blood flowing in the proper direction throughout the organ. If your heart is enlarged or the pressure in your heart is very high due to heart failure, these valves may not function properly.
• Heart rhythm problems: Heart rhythm problems (arrhythmias²⁸) can be a potential complication of heart failure.
• Liver damage: Heart failure can lead to a buildup of fluid in the liver that puts too much pressure on the organ. This fluid can lead to scarring, which makes it more difficult for the liver to function properly.

While some people’s heart failure symptoms and heart function will improve with proper treatment, the condition can be life-threatening. People with heart failure may have severe symptoms, and some may require procedures like heart transplantation or support with a ventricular assist device.

Congestive heart failure symptoms

The signs and symptoms²⁹ of heart failure may include:

• Shortness of breath (dyspnea) when you exert yourself or lie down
• Fatigue and weakness
• Swelling (edema³⁰) in your legs, ankles, and feet
• Rapid or irregular heartbeat (arrhythmia)
• Reduced ability to exercise
• Persistent cough or wheezing with white or pink blood-tinged phlegm
• Increased urge to urinate at night
• Swelling of the abdomen (ascites³¹)
• Very rapid weight gain from fluid retention
• Lack of appetite and nausea
• Difficulty concentrating or decreased alertness
• Sudden, severe shortness of breath and coughing up pink, foamy mucus
• Chest pain (if your heart failure is caused by a heart attack³²) If you believe that you have heart failure or if you experience any new or worsened symptoms of CHF, it’s important that you contact your healthcare provider immediately.

Congestive heart failure stages

The progression and severity of congestive heart failure can be classified in a number of ways.

Healthcare providers and specialists usually classify heart failure³³ according to the severity of a patient’s symptoms. The most commonly used classification is the New York Heart Association’s (NYHA) Functional Classification, which places patients in one of four categories based on how much they are limited during physical activity.

The following are used to classify patient symptoms:

• Class I: No limitation of physical activity. Ordinary physical activity does not cause undue fatigue, palpitation, or dyspnea (shortness of breath).
• Class II: Slight limitation of physical activity. Comfortable at rest. Ordinary physical activity results in fatigue, palpitation, or dyspnea.
• Class III: Marked limitation of physical activity. Comfortable at rest. Less than ordinary activity causes fatigue, palpitation, or dyspnea.
• Class IV: Unable to carry on any physical activity without discomfort. Symptoms of heart failure at rest. If any physical activity is undertaken, discomfort increases.

For example, a patient with severe angina³⁴ (chest pain) but angiographically normal coronary arteries (which, in tandem, would be described as anginal syndrome without evidence of coronary artery disease³⁵) would be classified as “Functional Capacity IV, Objective Assessment A.”

Congestive heart failure can also be classified according to the stage of its progression. The American Heart Association and American College of Cardiology’s staging system³⁶ places heart failure in stages from A–D:

• Stages A and B represent people who have not yet developed heart failure but are at high risk because of coronary artery disease, high blood pressure, diabetes, or other predisposing conditions.
• Patients with stage A heart failure show no objective evidence of cardiovascular disease, no symptoms, and no limitation in ordinary physical activity.
• Those with stage B heart failure show objective evidence of minimal cardiovascular disease. They have mild symptoms and slight limitations during ordinary activity and are comfortable at rest.
• Stage C includes patients with past or current symptoms of heart failure who have a condition called structural heart disease³⁷. They show objective evidence of moderately severe cardiovascular disease with marked limitation in activity due to symptoms, even during less-than-ordinary activity and are comfortable only while at rest.
• Stage D includes patients who have advanced heart failure that is difficult to manage with standard treatment. They show objective evidence of severe cardiovascular disease, with severe limitations and experience symptoms even while at rest.

In its early stages, heart failure can be managed with medication and a healthy lifestyle. As the disease progresses, however, treatment becomes more complex.

Advanced heart failure³⁸, which is identified as stage D, is heart failure that is difficult to treat with conventional heart therapies and symptom management. According to the American Heart Association, about 10% of the 6 million Americans living with CHF have advanced heart failure.

A person with advanced heart failure feels shortness of breath and other symptoms of CHF even while at rest.