Four words that sort a whole disease
Heart failure sounds like one thing. A heart that has failed. In reality it covers people who walk their dog every morning and people in intensive care, and treating them as a single group has always been one of cardiology's quiet problems.
In 1976, a team including James Forrester and George Diamond published a way to sort patients that is still in use half a century later. It needs only four words. Warm or cold. Wet or dry.
Warm means blood is getting to your organs and tissues properly. Cold means it is not: the heart's output is too low to keep everything well supplied.
Dry means fluid is not backing up into the lungs. Wet means it is: pressure inside the heart is high enough that fluid gets pushed into lung tissue.
Put those together and you get four profiles:
- Warm and dry: good flow, no congestion
- Warm and wet: good flow, but fluid backing up
- Cold and dry: poor flow, no congestion
- Cold and wet: poor flow and fluid backing up
Why the order of those profiles matters
When this was first measured, survival got progressively worse as you moved through that list. Warm and dry did best. Cold and wet did worst. Congestion alone raised the risk of death. Congestion plus poor flow raised it further still.
The original version was built for patients in intensive care after a heart attack. The measurements came from right heart catheterisation, where a tube is threaded through a vein into the heart and lungs to measure pressures directly. The cut-offs were a cardiac index below 2.0 litres per minute per square metre for "cold", and a pulmonary capillary wedge pressure of 18 mmHg or higher for "wet".
Those are hospital numbers from an invasive test. Nobody is going to thread a catheter into a stable outpatient every few months to check.
The argument this paper is making
The 2024 paper by Frank Dini and colleagues, writing for the Heart Failure Study Group of the Italian Society of Cardiology, makes a straightforward but ambitious case. Take this 1970s ICU sorting system, measure it without a catheter, and use it for ordinary outpatients.
The two tools they propose for doing that are:
- Echocardiography, the ultrasound scan of the heart most heart failure patients already have.
- Natriuretic peptides, a family of hormones the heart releases when it is under strain, measured with a blood test.
Combine the two, the authors argue, and a cardiologist can work out which of the four profiles a patient sits in during a normal clinic visit. Then treatment can be matched to the profile, instead of every patient getting the same drugs at the same doses.
The surprising statistic
Here is a number that caught my attention. Among ambulatory patients with heart failure with reduced ejection fraction, meaning people well enough to live at home, somewhere between 23% and 45% have low cardiac output. At the lower end that is people attending regular clinics. At the higher end, people waiting for heart transplants.
Even at the lower figure, that is nearly a quarter of patients whose organs are not getting enough blood flow, many of them walking around, looking stable, and getting treated with drugs mostly tested on people who were not in that situation.
That is the problem this whole series is about.
Why this matters to you
If you or someone you care about has heart failure, you have probably heard a lot about ejection fraction, the percentage of blood the heart pumps out with each beat. It is the number most heart failure is organised around.
This paper is essentially saying ejection fraction is not enough. Two people with the same ejection fraction can be in completely different situations: one warm and dry, one cold and wet. And they may need quite different treatment.
Over the next seven parts we will go through how that sorting works in practice. We will look at why ejection fraction falls short, what natriuretic peptides are and why your personal "dry" level matters, how echo reads pressures without a catheter, and why feeling stable is not the same as being stable. One part will lay out the serious weaknesses in this approach, because there are several. The last part is about the patients for whom standard doses may actually do harm, and what to ask about it.
Four words. A lot of consequences.
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.
