Systolic and diastolic heart failure describe two distinct ways the heart can fail to pump enough blood. In systolic heart failure, the heart muscle weakens and can’t squeeze forcefully enough. In diastolic heart failure, the heart squeezes normally but has become too stiff to fill with blood between beats. The distinction matters because the two types affect different people, show different changes on imaging, and respond to different treatments.
How Each Type Affects the Heart
Your heart works in two phases every time it beats. During systole, it contracts and pushes blood out to the body. During diastole, it relaxes and fills back up with blood. Heart failure can involve a problem in either phase.
In systolic heart failure, now formally called heart failure with reduced ejection fraction (HFrEF), the left ventricle enlarges and weakens over time. The muscle stretches out, the walls thin, and each contraction pushes out less blood than it should. A healthy heart ejects about 55% to 70% of the blood in the left ventricle with each beat. In systolic heart failure, that number (the ejection fraction) drops below 40%.
In diastolic heart failure, now called heart failure with preserved ejection fraction (HFpEF), the ejection fraction stays at 50% or above. The squeezing power looks normal on imaging. The problem is that the heart muscle has become thick and stiff, so it can’t relax properly between beats. Less blood fills the chamber, and pressure builds up behind it, backing into the lungs. The result is the same: not enough blood gets where it needs to go. There’s also a middle category, heart failure with mildly reduced ejection fraction, for people whose ejection fraction falls between 41% and 49%.
Structural Changes in the Heart
The two types reshape the heart in opposite ways. Systolic heart failure involves what cardiologists call eccentric remodeling. The heart muscle cells grow longer, stretching the chamber walls. The left ventricle dilates into a larger, thinner, balloon-like shape. On a chest X-ray, this often shows up as obvious enlargement of the heart.
Diastolic heart failure follows a concentric pattern. The muscle cells thicken rather than lengthen, and the walls of the ventricle grow inward. The chamber itself may stay normal-sized or even shrink slightly, but the walls become rigid. This is why standard chest X-rays can look deceptively normal in someone with diastolic heart failure, even though the heart is struggling.
Who Gets Each Type
The two types split the heart failure population roughly in half. Among over 2.6 million heart failure hospitalizations analyzed in a large national study, about 1.2 million were diastolic (HFpEF) and about 1.4 million were systolic (HFrEF). But the demographics look quite different.
Diastolic heart failure skews older and more female. The average age at hospitalization is around 75, and about 63% of patients are women. Systolic heart failure trends younger (average age around 70) and predominantly affects men, who make up about 61% of cases. High blood pressure and obesity are the most common drivers of diastolic heart failure, while prior heart attacks, valve disease, and conditions that directly damage heart muscle are more typical causes of the systolic type.
Symptoms Are Nearly Identical
This is what makes the two types so hard to tell apart without testing. Both cause shortness of breath (especially with exertion or lying flat), fatigue, swelling in the legs and ankles, and fluid buildup in the lungs. You can’t reliably distinguish one from the other based on symptoms alone.
One subtle clinical clue: systolic heart failure tends to present with a noticeably enlarged heart on physical exam and imaging, while diastolic heart failure more often shows signs of lung congestion (crackling sounds, difficulty breathing) with a normal or only slightly enlarged heart. But this pattern isn’t reliable enough on its own to make a diagnosis.
How Each Type Is Diagnosed
An echocardiogram, an ultrasound of the heart, is the primary tool for separating the two. It measures the ejection fraction directly. If it’s below 40%, that confirms systolic heart failure. If it’s 50% or above but the person has clear heart failure symptoms, the diagnosis shifts to diastolic heart failure.
Diagnosing diastolic heart failure requires an extra step because the ejection fraction looks normal. Doctors look for signs that the heart isn’t relaxing properly. One key measurement is the E/e’ ratio, which compares how fast blood flows into the ventricle with how fast the heart wall moves during filling. A ratio above 10 to 15 suggests the ventricle is abnormally stiff and filling pressures are elevated.
Blood tests also help. A protein called NT-proBNP rises when the heart is under strain. Levels below 50 pg/mL generally rule out heart failure, while levels above 125 pg/mL raise concern. These thresholds apply to both types and help confirm whether symptoms like shortness of breath are truly coming from the heart.
Treatment Differs Significantly
This is where the distinction between the two types matters most. Systolic heart failure has a well-established treatment playbook. Current guidelines recommend starting four classes of medication together, sometimes called “quadruple therapy”: a drug that blocks harmful stress hormones (beta-blockers), a drug that reduces fluid retention and scarring in the heart (mineralocorticoid receptor antagonists), a combined drug that helps blood vessels relax and protects the heart from damaging proteins (ARNi), and a newer class originally developed for diabetes that reduces heart failure hospitalizations (SGLT2 inhibitors). This combination has strong evidence for reducing death and hospitalization. For more advanced cases, implantable defibrillators and cardiac resynchronization devices may also be recommended.
Diastolic heart failure has historically been much harder to treat. For decades, no medication convincingly improved outcomes. Most treatments focused on managing symptoms: controlling blood pressure, reducing fluid with diuretics, and treating underlying conditions like obesity and diabetes. That changed with the EMPEROR-Preserved trial, published in the New England Journal of Medicine, which showed that the SGLT2 inhibitor empagliflozin reduced the combined risk of cardiovascular death or hospitalization in patients with diastolic heart failure regardless of whether they had diabetes. This made SGLT2 inhibitors the first drug class with solid evidence for this type of heart failure. Other medications that work well in systolic heart failure, like beta-blockers and ARNi, have shown only modest or inconsistent benefits in diastolic heart failure.
Why the Type of Heart Failure Matters
Knowing which type you have shapes nearly every treatment decision. A person with systolic heart failure who isn’t on all four recommended drug classes may be undertreated. A person with diastolic heart failure prescribed the same full regimen may not benefit from most of it. The distinction also affects prognosis, monitoring, and whether devices like defibrillators are worth considering.
If you’ve been told you have heart failure, the single most important number to know is your ejection fraction. It determines your category, guides your treatment, and serves as the baseline for tracking whether your heart is improving, stable, or getting worse over time.