What Are the Classifications of Heart Failure?

Heart failure (HF) is a complex syndrome caused by the heart not functioning properly. Different types of heart failure are classified by specific characteristics, including symptoms and limitations of function. Heart failure can have identifiable or unknown causes.^1-2 The diagnosis of heart failure, according to established guidelines, is based on criteria which include the presence of symptoms and signs, evidence of reduced cardiac function on diagnostic tests, and/or a favorable response to treatment.¹

There are multiple classifications of heart failure, but the two main ones are the New York Heart Association (NYHA) and the American College of Cardiology/American Heart Association (ACC/AHA) which have complementary classification systems. Your doctor will make a determination based on the severity of your symptoms and level of heart function.¹

New York Heart Association classification

Doctors usually classify patients' heart failure according to the severity of their self-reported symptoms. The classification system used most often is the New York Heart Association (NYHA) Functional Classification. Four levels of clinical classification are used to classify people according to symptoms and limitations experienced during physical activity. Symptom severity is compared to normal breathing, shortness of breath, and/or angina (chest pain or discomfort).¹ Classification of heart failure based on function during physical activity, often called exertion, is often an important indicator of prognosis.^1,2

• Class I: No limitation of physical activity. Ordinary physical activity does not cause symptoms of HF.
• Class II: Slight limitation of physical activity. Comfortable at rest, but ordinary physical activity results in symptoms of HF.
• Class III: Marked limitation of physical activity. Comfortable at rest, but less than ordinary activity causes symptoms of HF.
• Class IV: Symptoms occur even at rest; discomfort with any physical activity. Unable to carry on any physical activity without symptoms of HF.

Class I and II are typically considered mild heart failure, while class III and IV are considered more severe or advanced heart failure. A person can move back and forth between these classes as they are based on symptoms. When a patient has a heart failure exacerbation, they will have more symptoms and likely be a higher class, but when their symptoms are better controlled, they will be a lower class.

ACC/AHA classification

The American College of Cardiology (ACC) and the American Heart Association (AHA) worked together to create another classification system that complements the NYHA approach. It considers people who do not yet have HF but are at high risk for developing it.^2,3

The American College of Cardiology/American Heart Association (ACC/AHA) staging system defines four stages:⁴

• Stage A: High risk of heart failure but no structural heart disease or symptoms of heart failure (pre-heart failure)
• Stage B: Structural heart disease but no symptoms of heart failure (pre-heart failure)
• Stage C: Structural heart disease and symptoms of heart failure
• Stage D: Refractory heart failure requiring specialized interventions

The stages denote the level of risk for developing heart failure on through the development of advanced heart failure. The stages are progressive and correlated to treatment plans. As heart failure worsens, the condition advances to the next stage. There is no reverting back through the stages. With treatment, progression through the stages may be delayed.³ Diagnostic considerations include evaluating when heart failure starts, where it develops, how it impairs function, and whether or not it can be effectively managed with treatment.

Acute and chronic heart failure

People with acute heart failure (AHF) have no previous signs and symptoms of heart failure. AHF can present with rapid swelling and fluid retention characterized by sudden weight gain. Coughing, wheezing, and shortness of breath, as well as an irregular heartbeat, could be symptoms of acute heart failure. In some cases, it is related to pre-existing cardiomyopathy.^6-7 AHF often requires unexpected hospital admission. It can also be associated with a poor prognosis and a high risk of readmission and death post-discharge.⁸ Treatment options include medication, surgery, and implanted medical devices, as well as recommended lifestyle modifications.

Chronic heart failure (CHF) describes the heart’s inability to pump enough blood through the body and provide a sufficient supply of oxygen. This is caused by a weaker than a normal heart. CHF is most common in men and risk factors include age, high blood pressure, being overweight and the presence of metabolic disorders like diabetes. CHF is as its name describes - it is a long-term condition that can get worse over time. It generally cannot be cured but it can be medically managed.⁷

The two sides of the heart

The heart is a muscle that is divided into two halves: the left and right side of the heart. Each time the heart beats it transports oxygenated blood out into the circulatory system and refills with blood that needs to be replenished with oxygen by the lungs.⁸ The left ventricle is the main pumping portion of the heart and plays a key role in normal heart function. HF on the left-side means the heart has to work harder to squeeze out the same amount of blood. This is referred to as left ventricular (LV) heart failure. LV, the most common type of HF, is typically diagnosed based on results from an echocardiogram which is used to evaluate the ejection fraction (EF) of the left ventricle.^8-9

The right ventricle pumps the blood out of the heart into the lungs where it is replenished with oxygen. Right-sided heart failure is usually the result of chronic left-sided failure. As the left ventricle fails, increased fluid flows back through the lungs into the right ventricle, causing blood to back up in the veins leading to swelling and resulting in damage to the right side of the heart.⁸

Both sides of the heart can be affected, and this is called biventricular heart failure. It can present with symptoms that are similar to left and right-sided heart failure, including shortness of breath and swelling due to a build-up of fluid. Heart failure rarely develops on the right side first. It is the LVHF that contributes to the strain on the right side of the heart that causes HF to develop on both sides.¹⁰

Chronic heart failure

Chronic Heart Failure, also called congestive heart failure (CHF) occurs when the heart cannot fill properly or pump blood forward causing fluid to build up into the tissues of the body, resulting in congestion or swelling.^5,8 The typical symptoms are shortness of breath and fatigue. Not everyone with CHF will have congestion, some people only experience fatigue and decreased activity tolerance. Those who experience congestion may have swelling in the ankles and legs, abdomen, or lungs. Shortness of breath and pulmonary edema can lead to respiratory distress if not treated promptly.¹¹ Heart failure can also affect the kidneys' ability to process and eliminate sodium and water. This may result in even more fluid retention and subsequent swelling.³

Ejection fraction

The ejection fraction describes the pumping ability of the heart; a muscle that contracts and relaxes with every beat. The EF measures the percentage of blood pumped out of the heart each time it contracts. With every beat, the heart pumps blood throughout the body. When the pumping ability of the heart is impaired, the ejection fraction measurements decline.^4-5 The normal range for an EF is 55% to 70%.⁴

Diastolic heart failure

Also known as heart failure with preserved ejection fraction (HFpEF), diastolic HF develops when the left ventricle becomes rigid or stiff and cannot relax during diastole, the time between beats. This prevents the heart from properly refilling with blood.^12-13 Representing about half of all HF cases, diastolic heart failure is most common in older people and in women.^4,6,12-13 It is often present when there are other underlying medical conditions (comorbidities) that can contribute to the development of HF. HFpEF denotes a preserved ejection fraction because although the muscle cannot relax as well as it should, the left ventricle is still pumping normally.^12-13

Systolic heart failure

Also known as heart failure with reduced ejection fraction (HFrEF), systolic HF develops when the left ventricle does not contract normally. This means the heart no longer pumps with enough force to squeeze enough blood into circulation. Conditions like high blood pressure, arrhythmias, coronary artery disease, and abuse of alcohol and drugs can contribute to the development of heart failure.⁷ HFrEF progresses as the left ventricle, the lower-left chamber of the heart, gets larger and works harder to squeeze pump the right amount of oxygen-rich blood out to fuel the body.^4-8

Decompensated heart failure

Decompensated heart failure (DHF) occurs when patients who have known HF develop worsening signs and symptoms of congestion. This is also called fluid overload, as the body has more fluid than it can get rid of. Patients may have weight gain, worsening dyspnea, swelling or edema in their legs or abdomen, nausea, and are short of breath while lying down. Decompensated heart failure can also cause fatigue, making you feel more tired when doing vigorous or everyday activities. This can interfere with carrying out household activities or any strenuous tasks at work. These patients may need to be admitted to the hospital for treatment.