Heart failure with mildly reduced ejection fraction (HFmrEF)

Ejection fraction is the proportion of blood in the left ventricle that is pumped out with each heartbeat, usually measured by echocardiogram. A normal figure is around the mid-fifties or above. The BHF divides heart failure into three groups by that number: 50 per cent or above (preserved), 40 to 49 per cent (mildly reduced) and 40 per cent or below (reduced). The number is only one part of the picture, because symptoms and signs of fluid build-up, blood tests such as BNP, and structural changes on echo are also needed to diagnose heart failure.

Measurement has a margin of error, and different scan methods can give slightly different numbers. Someone sitting near 40 or 50 may move between categories on repeat tests, which is why clinicians look at trends and clinical status together.

HFmrEF contains several kinds of patient. Some have recovered from a lower ejection fraction after treatment and are described as having improved function; stopping treatment in these people can allow relapse. Others have a heart that is starting to deteriorate, typically from coronary artery disease or high blood pressure. Some have features resembling preserved ejection fraction, with stiff heart muscle and multiple other illnesses such as diabetes, kidney disease or obesity.

Because of this mix, investigation for cause matters. Tests may include a coronary assessment, cardiac MRI, rhythm monitoring and screening for thyroid problems, anaemia and kidney function, since the BHF lists arrhythmias, thyroid disorders and some cancer treatments among causes of heart failure.

The NHS lists breathlessness during everyday activities, fatigue, light-headedness, swelling in ankles and legs, sudden weight gain and night-time cough as common symptoms. Diagnosis involves blood tests, an ECG, chest X-ray and an echocardiogram, with MRI in some cases. A raised BNP or NT-proBNP supports the diagnosis and helps decide who needs a scan urgently.

• Breathlessness on walking, climbing stairs or lying flat.

• Ankle or leg swelling and rapid weight gain over days.

• Persistent tiredness and reduced exercise tolerance.

• Waking at night short of breath.

There is less trial evidence for HFmrEF than for HFrEF, so treatment is built around symptoms and the cause. The NHS describes medicines that reduce fluid build-up, widen blood vessels and slow heart rate, and these are tailored to the individual. Diuretics relieve congestion. Many cardiologists extend drugs proven in reduced ejection fraction, such as ACE inhibitors or related medicines, beta-blockers and mineralocorticoid antagonists, where they suit the person, and SGLT2 inhibitors are increasingly used across the spectrum. Treating high blood pressure, diabetes, coronary disease, atrial fibrillation and sleep apnoea is an equal priority.

Devices such as pacemakers or defibrillators are considered mainly when ejection fraction falls to the lower range or when there are rhythm problems. Cardiac rehabilitation, which the NHS recommends staying active through, improves fitness and confidence.

Weigh yourself regularly if advised and report a rapid gain. Take medicines as prescribed, follow guidance on salt and fluid, and ask about flu and pneumococcal vaccines, which the NHS includes in self-management advice. Stopping smoking and limiting alcohol are important. Repeat echocardiograms track whether the ejection fraction is improving, stable or falling, and your plan may change as a result.

The NHS advises urgent help (NHS 111 or same-day GP) for breathlessness when lying down, a pink frothy cough or rapid weight gain, and 999 for severe breathing difficulty, pale or blue lips or skin, or loss of consciousness.