For Your Patients: What Is Heart Failure?

— A brief overview of heart failure, its different classifications, and causes

Illustration of the letter i over a hand over a heart with cardiomyopathy

While heart failure can start in several ways, the key feature is that the heart stops doing an effective job of filling with blood and pumping it out to the rest of the body.

This complex clinical syndrome often starts in an at-risk individual (dubbed stage A of the disease) and progresses to structural or functional impairment of the heart without symptoms (stage B). It only becomes heart failure, though, once signs and symptoms become apparent (stage C). The final stage (D) is when heart failure symptoms interfere with daily life and cause repeated hospitalization despite use of guideline-recommended medications and other treatments.

To some people the term "heart failure" may seem to imply a sealed fate and doomed future. While heart failure should raise concern, thanks to modern heart failure treatments, many patients are able live high functioning, productive lives for many years after their diagnosis.

The severity of heart failure's impact on daily function is classified by the New York Heart Association (NYHA) criteria:

  • Class I doesn't limit physical activity, and ordinary activities don't cause undue fatigue, abnormal heart rhythms (palpitations), or shortness of breath (dyspnea)
  • Class II is comfortable at rest but limits physical activity slightly with some fatigue, palpitations, and shortness of breath when doing ordinary physical activities
  • Class III is comfortable at rest but causes marked limitation of physical activity due to fatigue, palpitations, and shortness of breath with even a little physical activity
  • Class IV has symptoms even at rest, and any level of physical activity increases the discomfort

Heart failure is broadly broken into classification by ejection fraction, which indicates what percentage of the normal amount of blood is pumped out of the lower chambers known as the ventricles. Although right-sided heart failure does occur (with too little blood pumped to the lungs to fill up on oxygen), heart failure typically involves problems with contraction of the left ventricle that sends oxygenated blood out to the rest of the body.

Heart failure with reduced ejection fraction (HFrEF) is when the ejection fraction percentage drops to 40% or less. Heart failure with mildly reduced ejection fraction (HFmrEF) is a new category that falls in the grey zone of 41-49%, just under the threshold for normal (50% or greater).

Another category introduced by the latest guidelines for doctors in 2022 was heart failure with improved ejection fraction (HFimpEF), which is when HFrEF improves on follow-up measurements to an ejection fraction greater than 40%, although the structure of the heart and other changes in function might not have returned to normal.

In heart failure with preserved ejection fraction (HFpEF), the heart pumps normally (an ejection fraction of 50% or greater) but is too stiff to fill properly.

Common causes of heart failure are chronic conditions that weaken or damage the heart muscles, like a heart attack, faulty heart valves, an abnormal heart rhythm, coronary heart disease, and inherited conditions. High blood pressure, diabetes, chronic kidney disease, and certain other conditions increase the risk of heart failure, as do aging, a family history of heart failure, and an unhealthy lifestyle (poor diet, lack of physical activity, smoking, and drug or heavy alcohol use).

"Medical Journeys" is a set of clinical resources reviewed by doctors, meant for physicians and other healthcare professionals as well as the patients they serve. Each episode of this 12-part journey through a disease state contains both a physician guide and a downloadable/printable patient resource. "Medical Journeys" chart a path each step of the way for physicians and patients and provide continual resources and support, as the caregiver team navigates the course of a disease.