A weak heart pump can go unnoticed
The left ventricle is the heart's main pumping chamber. When it squeezes poorly, doctors call it left ventricular dysfunction, often measured as a low ejection fraction. For a long time it may cause no symptoms at all: no shortness of breath, no obvious fatigue. According to the authors, this silent form affects 3% to 6% of the general population. It is linked to poorer quality of life and shorter life, but it can be treated when it is found, before it turns into heart failure.
The problem is that spotting it takes an echocardiogram, a heart ultrasound that measures ejection fraction, the share of blood pushed out with each beat. There is no cheap, simple screening test in the doctor's office.
What the researchers did
An electrocardiogram, or ECG (also called EKG), records the heart's electrical activity through stickers placed on the skin. It takes a few minutes and is available almost everywhere. The team wanted to know whether an AI could find hidden signs of a weak heart in this routine test.
The researchers gathered ECGs and echocardiograms from 44,959 patients at the Mayo Clinic. They trained a neural network, a type of AI that learns from examples, to recognize an ejection fraction of 35% or less from the ECG alone. The AI was then tested on a separate group of 52,870 patients it had never seen.
The results: 86% of weak hearts caught
In these 52,870 patients, the AI reached an area under the curve of 0.93, on a scale from 0.5 (a coin flip) to 1 (a perfect test). In practice, it caught 86.3% of patients whose heart pumped poorly (its sensitivity) and correctly cleared 85.7% of those with a normal heart (its specificity). That also means about 14% of people with a normal heart got a false alarm.
The most striking finding is about those false alarms. Among patients whose heart still pumped normally, those flagged by the AI were 4 times more likely to develop a weak heart later than those who were not flagged. The AI seems to pick up very early changes on the ECG.
Key figures
- 3% to 6%of the general population has a weak heart pump without symptoms
- 0.93area under the curve in 52,870 patients, with 86.3% sensitivity and 85.7% specificity
- 4 timesthe risk of later developing a weak heart when the AI flagged a heart that was still normal
Short of breath or tired? Bring it up with Mima
This study shows that an ECG read by AI can flag a weak heart pump, but any alert still has to be confirmed with an echocardiogram. If ECGs are part of your care, it is something to discuss with your doctor, not a diagnosis.
Mima helps you note shortness of breath, tiredness or swollen ankles day by day, so you can share a clear picture at your appointment. You can prepare a question such as: "Could my ECG or a heart ultrasound show how well my heart is pumping?"
What this could mean for patients
The ECG is one of the most common and cheapest tests in medicine. If an AI can use it to flag a weak heart, a primary care doctor could order an echocardiogram for the right people sooner and start treatment before symptoms appear. The authors see the ECG becoming a powerful screening tool for people without symptoms.
The AI does not make a diagnosis. Any alert still needs to be confirmed with an echocardiogram.
The limits of this study
This is a retrospective study: it looked back at tests already done within one health system. Everyone studied had had an echocardiogram, often for a medical reason, so they may not reflect the general population. Trials were still needed to show that the tool truly helps doctors and patients in everyday care.
Also, with about 14% false alarms, very broad screening could send many people for an echocardiogram they did not need. The best way to use this tool is still being worked out.
Frequently asked questions
Can an EKG detect a weak heart or heart failure?
A standard ECG does not measure how well the heart pumps. In this study, an AI learned to spot signs of a weak heart pump on the ECG, but an echocardiogram is still needed to confirm it.
What is a low ejection fraction?
It means the left ventricle pushes out too small a share of its blood with each beat. This study focused on an ejection fraction of 35% or less.
Does an AI ECG replace an echocardiogram?
No. It helps flag who should get an echocardiogram. About 14% of people with a normal heart got a false alarm in this study.
Can you have a weak heart without symptoms?
Yes. According to the study, 3% to 6% of the general population has left ventricular dysfunction without symptoms, and it can be treated once found.
The original study
Attia ZI, Kapa S, Lopez-Jimenez F, et al. “Screening for cardiac contractile dysfunction using an artificial intelligence-enabled electrocardiogram” Nature Medicine, January 7, 2019. DOI : 10.1038/s41591-018-0240-2
Read the full study in Nature MedicineThis article summarizes a scientific study and is not medical advice.