About 6.7 million American adults live with heart failure, and roughly 1 in 4 people will develop it in their lifetime. Yet the way it is described in a clinic letter, "stage C, NYHA class II, reduced ejection fraction," can leave people more worried and less informed than before. Heart failure does not mean the heart has stopped or is about to; it means the heart is not pumping or filling as well as the body needs. And the outlook has changed substantially in the past decade, because the core medicines now protect the heart rather than only relieving symptoms. This guide explains the two systems doctors use, ACC/AHA stages and NYHA classes, what ejection fraction adds, what affects life expectancy, the treatments that change the course, and research for people living with heart failure today.
Living with heart failure or another heart condition?
These studies are testing new treatments for heart conditions, usually added on top of the medicines you already take.
Two systems, two different questions
Heart failure is described in two complementary ways. The ACC/AHA stage answers "how far has the disease progressed?" and only moves forward. The NYHA class answers "how much does it affect you right now?" and can go up or down with treatment. Knowing both, plus your ejection fraction, gives the clearest picture.
Our heart failure treatment guide explains how each shapes treatment.
The heart failure stages: A, B, C, and D
Stage A, at risk. No heart damage or symptoms yet, but conditions that raise the risk, such as high blood pressure, diabetes, coronary artery disease, obesity, or a family history of cardiomyopathy.
Stage B, pre-heart failure. Changes in the heart's structure or function, or blood markers of strain, but no symptoms.Treating it can prevent or delay symptoms, and some heart changes at this stage can improve.
Stage C, symptomatic heart failure. Heart disease with current or past symptoms such as breathlessness, fatigue, or swelling. This is the stage most people mean by heart failure, and where most treatment and research are focused.
Stage D, advanced heart failure. Severe symptoms or repeated hospital stays despite optimal treatment, where options such as heart pumps, transplant, or palliative care are considered.
The NYHA classes: I to IV
Class I: no limitation; ordinary activity does not cause symptoms.
Class II: slight limitation; comfortable at rest, but ordinary activity such as climbing stairs causes breathlessness or fatigue.
Class III: marked limitation; comfortable at rest, but less than ordinary activity, such as walking across a room, causes symptoms.
Class IV: symptoms at rest, and any activity makes them worse.
Because the class reflects how you feel now, good treatment can move someone from class III to class II or even class I, while their stage stays C. That is one of the most encouraging facts about heart failure: the class is not a sentence.
What ejection fraction adds
Ejection fraction is the share of blood the left ventricle pumps out with each beat, measured by echocardiogram. Heart failure with reduced ejection fraction (HFrEF, 40 percent or less) and heart failure with preserved ejection fraction (HFpEF, 50 percent or more) behave differently and are treated differently, with a mildly reduced group in between. Many treatments and studies are specific to one type, so it is worth knowing which one you have.
Heart failure life expectancy
Heart failure is serious, and older studies found that about half of people with heart failure died within five years of diagnosis. But averages from the past understate what is possible now. Outcomes depend heavily on the type of heart failure, the NYHA class, how often you are hospitalized, kidney function, age, other conditions, and above all whether you are on the full set of recommended medicines. Mortality is highest in class IV and stage D. Your cardiologist, who knows your numbers, is the right person to discuss what to expect.
The treatments that change the course
For heart failure with reduced ejection fraction, the 2022 American guideline recommends four classes of medicine taken together, often called the four pillars: an ARNI or ACE inhibitor or ARB, a beta blocker, a mineralocorticoid receptor antagonist such as spironolactone, and an SGLT2 inhibitor such as dapagliflozin or empagliflozin. Each one independently lowers the risk of hospitalization and death, and many people are not yet on all four. Devices such as defibrillators and resynchronization pacemakers help selected patients. For mildly reduced and preserved ejection fraction, SGLT2 inhibitors are central, finerenone (Kerendia) was approved in July 2025, and treating blood pressure, atrial fibrillation, and weight matters too. Our guide to new medications for heart failure goes into detail.
How to find a heart study
AllClinicalTrials.com lists cardiovascular studies recruiting across the US, and you can filter by location before applying. Right now that includes a large group of studies for adults with heart failure and other heart conditions, including coronary artery disease, atrial fibrillation, high blood pressure, and high cholesterol, for people already taking medicine for their heart. The application takes about 5 minutes: you answer questions about your diagnosis, symptoms, and medicines, and if a study near you looks like a match, the research team contacts you. Nothing is decided until you have gone through informed consent, and participation is voluntary at every step. More studies are on our heart failure clinical trials page.
Three things to have ready: your type of heart failure and ejection fraction if you know them, how much daily activity is limited by breathlessness or fatigue, and the list of medicines you take for your heart.
Common questions
What are the 4 stages of heart failure? Stage A (at risk, no heart changes), stage B (heart changes but no symptoms), stage C (symptoms of heart failure), and stage D (advanced heart failure despite treatment).
What is the difference between heart failure stages and NYHA classes? Stages describe how far the disease has progressed and only move forward. NYHA classes describe how much it limits you now, from I to IV, and can improve with treatment.
Can heart failure stages improve? The ACC/AHA stage does not move backward, but heart function and symptoms can improve. NYHA class often improves with good treatment, for example from class III to class II.
What is the life expectancy with heart failure? It varies widely by type, NYHA class, hospital admissions, kidney function, age, and treatment.Older studies found about half of people with heart failure lived five years, but modern treatment has improved the outlook; your cardiologist can give a personal estimate.
What are the four pillars of heart failure treatment? For reduced ejection fraction: an ARNI or ACE inhibitor or ARB, a beta blocker, a mineralocorticoid receptor antagonist, and an SGLT2 inhibitor. Each lowers the risk of hospitalization and death.
What does NYHA class III mean? You are comfortable at rest, but less than ordinary activity, such as walking a short distance, causes breathlessness, fatigue, or palpitations.
Do heart trial participants get paid? Some studies offer compensation for time and travel, and study related care is typically provided at no cost to participants. Compensation varies by trial and is always described during the informed consent process before you agree to anything.
See Heart Failure clinical trials recruiting now
Browse open studies, filter by location, and apply in about 5 minutes: Heart Failure Clinical Trials.