Heart Failure with Mildly Reduced Ejection Fraction

Heart failure with mildly reduced ejection fraction is a type of heart failure with a left ventricular ejection fraction of 41 to 49%. Ejection fraction is the percentage of blood in the left ventricle that is pumped out each time the heart beats; in a healthy heart, it is usually 50% or higher. A value of 41 to 49% lies between heart failure with reduced ejection fraction (40% or lower) and heart failure with preserved ejection fraction (50% or higher). The heart's pumping strength is already reduced, but not as low as in the reduced type.

This type used to be called mid-range, meaning in the middle range. Since the 2021 ESC guidelines and the universal definition of heart failure, it has been called mildly reduced. This name change reflects findings that this type is more similar to reduced ejection fraction, including in its response to some medicines.

Features and Causes

As with the reduced type, coronary artery disease is a common cause, and this type is found more often in men. Other causes include long-standing hypertension, valve disease, atrial fibrillation, and cardiomyopathy. The symptoms are the same as in other types of heart failure: shortness of breath, tiring easily, and swelling in the legs. The diagnosis becomes stronger when there is evidence of structural heart changes, such as an enlarged left atrium or a thickened ventricular wall.

An Ejection Fraction That Can Change

The ejection fraction in this type often changes over time. Some people previously had an ejection fraction of 40% or lower that then improved with treatment, a state called improved ejection fraction. Others instead drop into the reduced group, for example after a new heart attack. For this reason, your doctor repeats echocardiography regularly, and the history of your ejection fraction values also helps determine the choice of medicines.

Treatment Approach

The 2023 ESC guideline update recommends SGLT2 inhibitors for this type, based on the DELIVER and EMPEROR-Preserved trials, because they reduce the combined outcome of hospitalization for heart failure and cardiovascular death. Diuretics are used to relieve fluid congestion. Medicines used in reduced ejection fraction, such as beta blockers, ACE inhibitors, ARBs, ARNIs, and MRAs, may be considered by your doctor depending on your situation. The underlying cause and coexisting conditions are also treated, because both affect how the disease progresses.

The first steps are the same as for other types of heart failure: questions about your symptoms, a physical examination, an ECG, and an NT-proBNP or BNP test. Echocardiography determines the ejection fraction. If the value is 41 to 49%, your doctor also looks for signs of structural heart changes, such as an enlarged left atrium or a thickened wall, and reviews previous echocardiography results to see which way the ejection fraction is moving: improving or declining.

Because coronary artery disease is often the cause, your doctor may recommend CT coronary angiography, a stress test, or coronary angiography. Cardiac MRI helps assess scar tissue and other causes. Echocardiography is repeated after treatment has been underway for a few months or if your symptoms change.

See a cardiologist if you start tiring quickly, become short of breath during activities that used to be light, or have swelling in your legs, especially if you have coronary artery disease or hypertension. If you have already been diagnosed, contact your doctor early if any of the following occur.

• Your weight goes up by 2 kg or more in 3 days.
• Shortness of breath or swelling gets worse, or you need higher pillows to sleep.
• Your heart pounds or your pulse feels irregular.
• You feel dizzy or weak after a change in medicines.
• Go to the emergency room right away if you have severe shortness of breath at rest, chest pain, or fainting.