You have been told you have heart failure, and within the same conversation you have heard HFrEF, HFpEF, and perhaps HFimpEF. It sounds like alphabet soup, and it arrives at exactly the moment you are least equipped to decode it. The good news is that these terms are far less frightening once you understand what they are actually measuring, and why your cardiologist cares about the difference.

This article breaks the language down into plain English: what heart failure really means, what those letters stand for, why the distinction matters for your treatment, and what a major new international definition, published in June 2026, changes for patients.

Start With What Heart Failure Actually Means

The name is one of the cruellest in medicine. “Failure” suggests something has stopped, or is about to. That is not what it means. Heart failure is a clinical syndrome in which the heart cannot pump or fill with blood as efficiently as the body needs, usually producing symptoms such as breathlessness, fatigue, and swelling in the legs and ankles.

Crucially, it is not a single disease and it is not a death sentence. It is a description of how the heart is performing, and modern treatment can stabilise it, ease symptoms, and in a meaningful number of people improve the heart’s function substantially. To understand the categories, you first need to understand one number.

The Number Behind the Letters: Ejection Fraction

Every time the heart’s main pumping chamber, the left ventricle, contracts, it squeezes a percentage of the blood inside it out to the body. That percentage is the ejection fraction, usually shortened to EF. It is measured most often on an echocardiogram, the heart ultrasound.

A normal left ventricle does not empty completely. A healthy EF sits somewhere around 55% to 70%. So an EF of 60% is normal, not a sign that 40% is being left behind in a worrying way. This is the single most misread number in a cardiology report, so it is worth pausing on: a lower EF means the pump is weaker, but the EF is only one part of the picture, and it is not the whole story of how you will feel or fare.

The Three Main Types, Explained

Heart failure is grouped by ejection fraction because that number, more than almost anything else, tells the cardiologist what kind of problem they are dealing with and which treatments are likely to help. Here are the categories you are most likely to hear.

HFrEF: heart failure with reduced ejection fraction

This is the “weak pump” type. The EF is reduced, conventionally 40% or below, meaning the left ventricle is not contracting forcefully enough. The heart muscle has usually been damaged or weakened, and the squeeze is impaired. HFrEF is the type with the largest body of evidence behind its treatment, and, importantly, the type where the right combination of medicines can make the biggest difference.

HFpEF: heart failure with preserved ejection fraction

Here the EF is preserved, conventionally 50% or above, so the pump looks normal on paper. The problem is not the squeeze but the relaxation and filling. A stiff left ventricle cannot relax properly between beats, so it fills poorly and pressure backs up, producing the same symptoms of breathlessness and swelling. HFpEF is more common in older adults, in women, and in people with long-standing high blood pressure, diabetes, or obesity. For years it was the harder type to treat, though that has changed recently.

HFimpEF: heart failure with improved ejection fraction

This is the newest and most hopeful category. It describes someone who started with a reduced EF (40% or below) and, with treatment, has seen it recover to above 40%. Their heart has improved. The vital message attached to this label, and the reason cardiologists coined it rather than simply calling the person “better,” is that the improvement is usually because of the medicines, not instead of them. Stopping treatment because the numbers look good is one of the most common ways people relapse.

You may also hear HFmrEF, heart failure with mildly reduced ejection fraction, describing the middle band where EF sits between 41% and 49%. Think of it as the territory between the reduced and preserved categories, treated with a foot in both camps.

Why Cardiologists Bother Splitting Hairs

It is a fair question. If the symptoms are similar, why label the types at all? The answer is that the underlying mechanics are genuinely different, and so is the treatment that works. A medicine proven to save lives in a weak, reduced-EF heart may do little for a stiff, preserved-EF heart, and vice versa. The category is not bureaucratic tidiness. It is the shorthand that points your whole care team toward the treatments most likely to help you, and away from ones that will not.

Getting the category right also shapes what your cardiologist watches over time, from your BNP blood test to repeat scans that track whether your EF is holding steady, worsening, or improving.

The table below sets the three types side by side. It is a map, not a diagnosis, and your own cardiologist remains the person who reads it onto your particular heart.

The label is not there to frighten you. It is there to make sure the right medicine reaches the right heart.

What Causes Each Type

The causes overlap, but they cluster differently across the categories, and identifying the cause is often as important as measuring the EF.

Reduced-EF heart failure most often follows damage to the heart muscle: a previous heart attack that has left a weakened area, longstanding uncontrolled blood pressure, disease of the heart muscle itself (the cardiomyopathies), heart rhythm problems such as atrial fibrillation, valve disease, or, in some people, alcohol and certain toxins.

Preserved-EF heart failure tends to grow out of years of a heart working against stiffening and pressure: chronic high blood pressure, diabetes, obesity, obstructive sleep apnoea, and ageing itself. Less commonly, an infiltrative condition such as cardiac amyloidosis stiffens the muscle, which matters because some of these causes now have specific treatments.

Improved-EF heart failure, by definition, starts as the reduced type and gets better, usually because the cause was treatable and the treatment worked. That is precisely why the medicines are rarely a temporary measure.

How Each Type Is Treated

This is where the categories earn their keep. The following is a general map, not a prescription. The right combination, and every dose, is individual, and only your own cardiologist can advise what is right for you.

For reduced-EF heart failure, the modern approach uses four classes of medicine together, often called the four pillars or quadruple therapy. In broad terms these are a medicine that relaxes and protects the blood vessels and heart (an ACE inhibitor, an ARB, or the combination agent Entresto), a beta-blocker, a mineralocorticoid receptor antagonist such as spironolactone, and an SGLT2 inhibitor. Used together and built up carefully, this combination has transformed outcomes over the past decade.

For preserved-EF heart failure, the picture has brightened considerably. SGLT2 inhibitors now have good evidence here too, which was not the case a few years ago. Beyond that, the priority is treating the drivers: controlling blood pressure and diabetes, managing weight, addressing sleep apnoea, and using diuretics to clear the fluid that causes congestion and breathlessness. Treating the specific cause, where there is one, matters more in this group than in any other.

For improved-EF heart failure, the treatment is, in most cases, to keep going. Trials have shown that stopping the medicines once the heart has recovered often allows the weakness to return. The recovery is best understood as the treatment succeeding, not as the illness disappearing, and the safest path is to maintain the therapy under your cardiologist’s guidance. Never stop a heart failure medicine without speaking to them first.

What the New 2026 Definition Changes

In June 2026, the world’s leading cardiovascular bodies, including the American Heart Association, the American College of Cardiology, the European Society of Cardiology, and the World Heart Federation, published the Second Universal Definition of Heart Failure, simultaneously in the journals JACC, Circulation, the European Heart Journal, and Global Heart. The American Heart Association has also released a plain-language summary for patients. It updates the first such definition from 2021, and although the document is written for clinicians, several of its changes matter to patients.

First, it moves away from rigid cut-off numbers for ejection fraction and acknowledges that a normal EF differs by sex, age, and ethnicity, while keeping the familiar reduced, preserved, and improved categories as practical guides. Second, it puts far greater emphasis on catching heart failure early, before symptoms appear, so that prevention and treatment can start sooner. Third, and perhaps most reassuringly, it formally describes heart failure as a dynamic condition that can improve, go into remission, or progress, rather than a fixed, one-way diagnosis. The document is intended to be the foundation for the next major heart failure guideline, expected in 2027.

For a patient, the takeaway is encouraging: the field increasingly sees heart failure not as a static verdict but as a condition to be caught early, categorised accurately, and, in many people, improved.

Conclusion

The terminology around heart failure sounds far more alarming than the reality for most people. HFrEF, HFpEF, and HFimpEF are simply three ways of describing how well the heart’s main chamber is pumping and filling, and each points toward a different and increasingly effective set of treatments. The letters are a tool for getting you the right care, not a measure of how worried you should be.

If you have been given one of these labels, the most useful thing you can do is understand which type you have, take the medicines as prescribed even if you feel well, and keep the conversation with your cardiologist going. Heart failure is more treatable today than at any point in medical history, and, as the newest category reminds us, it can genuinely improve.

Related Reading

• Heart Failure With Reduced Ejection Fraction: Why Quadruple Therapy Changed Everything
• SGLT2 Inhibitors: The Diabetes Drug That Transformed Heart Failure Treatment
• How to Lower Blood Pressure Naturally
• Obstructive Sleep Apnoea and the Heart: Why It’s So Often Missed
• Shortness of Breath and the Heart: When Breathlessness Is a Cardiac Signal
• Cardiac Amyloidosis: The Stiff Heart Condition That’s Now Treatable
• Understanding Your Cardiovascular Risk Factors