The number everyone gets told
If you have heart failure, you almost certainly know your ejection fraction. It is the percentage of blood in the main pumping chamber, the left ventricle, that gets pushed out with each beat. A healthy heart ejects somewhere over half. Heart failure is usually split into "reduced", "mildly reduced" and "preserved" ejection fraction, and a lot of treatment decisions hang off which category you fall into.
It is a useful number. This paper argues it is also a limited one, and it lists the problems plainly.
Five things ejection fraction gets wrong
The authors name five specific limitations.
1. It does not match real contractility. Ejection fraction is a ratio of volumes. It does not directly measure how hard the heart muscle is squeezing. A heart can have a reasonable ejection fraction and still have weak muscle, or vice versa, depending on how full the chamber is and what pressures it is working against.
2. It varies between observers. Two skilled people reading the same scan can come up with different numbers. For a measurement that decides which drug category you are in, that is not ideal.
3. It does not track symptoms well. Two people with the same ejection fraction can feel completely different. One is breathless climbing stairs, the other walks for an hour. Ejection fraction does not explain the difference.
4. It is imprecise for predicting risk. Within the group with reduced ejection fraction, the number alone does not do a great job of separating people who will do well from people who will not.
5. It oversimplifies. It compresses a complicated set of pressures and flows into one percentage.
What gets lost
Go back to the four profiles from Part 1. Warm or cold is about how much blood is reaching your tissues. Wet or dry is about pressure backing fluid into your lungs.
Ejection fraction does not tell you either.
You can have a reduced ejection fraction and be warm and dry, doing fine on standard drugs. You can have exactly the same ejection fraction and be cold and wet, with poor organ blood flow and fluid in your lungs. Ejection fraction puts both people in the same box.
That is the core complaint. It is not that ejection fraction is useless. It is that heart failure management is built around a number that misses two of the things that most directly predict how you will do.
What the better measurements are
The measurements that actually capture flow and congestion are:
Cardiac output and cardiac index. Cardiac output is how much blood the heart moves per minute. Cardiac index adjusts that for body size. Along with how much oxygen the blood gives up to tissues, these are the major factors deciding whether your organs are getting enough oxygen.
Left ventricular filling pressure. This is the pressure inside the heart as it fills between beats. When it climbs too high, the pressure transmits backward into the lungs and fluid seeps out. Pulmonary capillary wedge pressure, the catheter measurement from the original 1976 system, is a stand-in for this. It tells you about fluid moving into the lungs, and so about congestion.
Both of these used to require a catheter. The paper's argument, which we will get into in Part 5, is that echocardiography can now estimate them well enough to be useful.
The GUIDE-HF clue
The strongest evidence in the paper that pressure-based management works comes from a trial called GUIDE-HF. Patients had a small sensor implanted in the pulmonary artery that continuously measured pressure. Their treatment was adjusted based on those readings.
The paper reports that this approach reduced heart failure events across the whole range of ejection fractions in a large population. The benefit looked possible in patients with moderate symptoms who had either been hospitalised for heart failure before or had raised natriuretic peptide levels.
The important phrase there is "across the range of ejection fractions". The pressure mattered regardless of what the ejection fraction was. That is exactly the point this paper is trying to make.
Earlier work backs it up. Studies going back to the 1990s showed that therapy tailored to bring filling pressures down could keep them down over time, with better outcomes. And importantly, the high filling pressures that cause symptoms were not needed to keep the heart pumping enough blood. You can lower the pressure without sacrificing output.
A practical way to think about it
Here is how I would put it if you were sitting across from me.
Your ejection fraction tells you something about the shape of your heart's problem. It does not tell you how your body is coping with it right now.
For that you need to know two things: is enough blood getting where it needs to go, and is fluid backing up where it should not? Those two questions are what this paper is built around.
If your ejection fraction is the only heart number you know, it is worth asking your cardiologist what your last scan said about filling pressures and output. Many standard echo reports already include estimates. They just rarely get explained to the patient.
In Part 3 we turn to the blood test side: the peptide your heart releases when it is stretched.
This series discusses a peer-reviewed clinical review. Nothing here is medical advice. Heart failure treatment should always be guided by your own cardiology team.
