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What Is Heart Failure, and What are the Four Stages of Heart Failure?

Written by Todd Neff on behalf of National Jewish Health

The term “heart failure” seems simple enough. It’s about our life-giving pump breaking down. But there’s a whole lot more to this life-threatening condition that affects more than 6 million U.S. adults in a given year.

Heart failure has many risk factors:

  • Age (the older you are, the higher the risk)

  • Family history (that is, genetics)

  • Lifestyle factors (diet, obesity, physical activity)

  • Chronic conditions such as high blood pressure and type 2 diabetes

Heart Failure Has Different Names 

There’s acute heart failure, where an injury to the heart from a heart attack, chemotherapy, or other insults triggers a quick downward spiral.

Chronic heart failure is more common.  The heart slowly loses its pumping power and, with time, brings symptoms including fluid buildup, flagging energy, and difficulty breathing.


Heart Failure Is Classified by the Part of the Heart it Affects 

Left-sided heart failure impacts the left ventricle, which pumps blood to the body. It’s by far the most common.

Right-sided heart failure impacts the right ventricle, which pumps blood to the lungs. Typically, right-sided heart failure is caused by ongoing stresses from left-sided heart failure.


Heart Failure Is Classified by Cause

Heart failure also gets classified by how it’s causing the heart to fail. There are two main categories:

1. The first is heart failure with reduced ejection fraction (HFrEF, pronounced “hef-ref”), also known as systolic heart failure. A healthy heart ejects 55% to 70% of the blood that enters it with each beat. HFrEF starts at 40%.

2. The second category is heart failure with preserved ejection fraction (HFpEF, pronounced “hef-pef”). This is also called diastolic heart failure. That’s when a heart stiffened or thickened from scarring, amyloidosis, or other causes can’t fill properly. As a result, it pumps out too little blood with each beat even though its ejection fraction is normal.

Each category accounts for about half of heart failure cases, with HFpEF more prevalent among older patients and women.


How Severe Is Heart Failure?

Heart failure also varies in severity, which cardiologists specializing in heart failure have classified into stages of heart failure. There are two main ways to classify heart failure stages:

  1. The New York Heart Association classification focuses on how patients are feeling uses roman-numeral classifications of one through four.
  • Class I heart failure means no symptoms at all, even with strenuous activity.

  • Class II involves feeling fine at rest, but having mild symptoms such as fatigue, shortness of breath, chest pain, or discomfort during normal physical activity.

  • Class III is similar to class II in that symptoms don’t typically happen at rest, but they emerge with less-than-ordinary physical activity.

  • “With class II, you can most do daily living activities without a problem, but with class III, you can’t go on a walk without symptoms, and you can be short of breath at rest,” said National Jewish Health cardiologist and heart failure specialist Ankie Amos, MD.

  • Class IV heart failure involves frequent symptoms, even at rest. There is discomfort with even minor physical activity. “You’re short of breath at rest, and you probably need hospital admission,” Dr. Amos said.

  1. The American College of Cardiology and the American Heart Association, focuses more on what’s happening with the heart itself.
  • The American College of Cardiology and American Heart Association also classifies heart failure into four categories, but denotes them through stages A, B, C, and D.

  • Those in stage A show no evidence of heart disease, but people are at risk of heart failure due to family history, high blood pressure, or other risk factors. “The goal here is prevention,” Dr. Amos said.

  • Stage B heart failure patients have no heart failure symptoms, but do show abnormal heart function.

  • “So, for instance, on an ultrasound of the heart, you might have a weakened heart with an ejection fraction of 45% or 50%,” Dr. Amos said. “Or you might have a really thick heart that the patient has never noticed because they don’t have symptoms such as shortness of breath of fluid retention. So it’s asymptomatic heart failure.”

  • Patients in stage C have both structural heart problems and noticeable symptoms. Often, they end up seeking medical care for symptoms such as shortness of breath and find out that heart failure is the cause.

  • “The majority of patients diagnosed with heart failure are in stage C,” Dr. Amos said, adding that most treatment options target these patients.

  • Stage D patients have advanced heart failure in which most treatment options have been exhausted, hospitalizations are frequent, and organs start to fail. “You need an intervention, or death is imminent in the next six months, basically,” Dr. Amos said.

Understanding the nature and stages of heart failure are an important start. For those at risk or already experiencing symptoms, seeing a primary care doctor and getting referred to a cardiologist specializing in heart failure should be a top priority, Dr. Amos says.

The earlier heart failure diagnosed and treated, the better off you will be.

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