What Is Preserved LV Systolic Function?

Preserved left ventricular (LV) systolic function means the heart’s main pumping chamber is still contracting well enough to push a normal proportion of blood out with each beat. Doctors gauge this primarily through a measurement called ejection fraction, and in healthy adults the average sits around 63%, with anything above roughly 50% considered preserved. The term matters most in the context of heart failure, because about half of all new heart failure cases now involve people whose hearts appear to squeeze just fine on an ultrasound, yet who still experience debilitating symptoms like breathlessness and fatigue.

How Doctors Measure Systolic Function

The standard yardstick is left ventricular ejection fraction, or LVEF. It represents the percentage of blood the left ventricle ejects during each contraction. An echocardiogram, the ultrasound scan of the heart, is the most common way to obtain this number. A large meta-analysis of population-based studies found the average LVEF in healthy adults to be about 63%, with women averaging slightly higher than men. Fewer than about one percent of healthy women and roughly one percent of healthy men fall below 50%.¹

That 50% threshold is important because it is the conventional cutoff below which systolic function is labeled “reduced.” Clinicians group heart failure into three broad categories based on ejection fraction. People with an LVEF at or above 50% are said to have preserved ejection fraction. A middle band, roughly 40–49%, is sometimes called mildly reduced. Below 40% is clearly reduced systolic function. Heart failure with preserved ejection fraction (HFpEF) carries lower cardiovascular event risk than the reduced type, but the medications that work well for reduced ejection fraction often do not help as much when systolic function is preserved.²

Ejection fraction, however, has well-known technical limitations. Because echocardiography estimates a three-dimensional volume from a two-dimensional image, it relies on geometric assumptions about the shape of the ventricle. When the ventricle is distorted, as it can be after a heart attack, those estimates become less reliable.³ This means a single snapshot of ejection fraction can sometimes be falsely reassuring.

Why People Can Have Heart Failure With Normal Pumping

This is the part that surprises many people. Heart failure does not always mean the heart is too weak to squeeze. In HFpEF the problem is usually with filling rather than emptying. During the relaxation phase of each heartbeat, the left ventricle needs to loosen up and expand so blood can flow in from the left atrium. When the muscle becomes stiff, filling pressures rise, fluid backs up into the lungs and body, and the classic symptoms of heart failure appear: shortness of breath, swelling in the legs, and exercise intolerance. The recognition that a normal ejection fraction does not rule out heart failure has been one of the most important shifts in cardiology over the past two decades.⁴

HFpEF now accounts for roughly half of all new heart failure diagnoses, and it is especially common in older women and people with obesity, high blood pressure, or diabetes.⁵ These comorbidities are thought to drive adverse changes in the heart muscle itself, with close to half of all HFpEF patients showing thickened heart walls or concentric remodeling, a pattern where the muscle grows inward and the chamber gets smaller.⁶ Scar tissue, or fibrosis, accumulates in the heart muscle and increases stiffness, raising filling pressures and worsening exercise tolerance.

Hidden Systolic Problems Beneath a Normal Ejection Fraction

One of the key insights of the past decade is that “preserved systolic function” is sometimes an overstatement. Ejection fraction is a blunt tool. It tells you how much the chamber volume changes, but it can miss subtle problems with how the heart muscle actually deforms during contraction. A technique called global longitudinal strain (GLS) measures how much the muscle fibers shorten in their long axis, and it picks up dysfunction that ejection fraction misses.

In patients hospitalized with HFpEF, a high proportion have abnormal GLS values, indicating unrecognized systolic dysfunction hiding behind a normal-looking ejection fraction. Worse GLS in these patients has been linked to worse short-term outcomes.⁷ A systematic review pooling data from dozens of studies reported a wide range of GLS values in HFpEF patients, consistently worse than in healthy people.⁸ So when someone tells you their ejection fraction is normal, the heart may still not be squeezing as well as that number implies.

Exercise Intolerance and What Causes It

The hallmark complaint in HFpEF is not chest pain or fainting; it is exercise intolerance. Patients feel exhausted and breathless with activity levels that used to be easy. For years, this was attributed almost entirely to stiff ventricles and poor filling. The current understanding is far broader. Impaired exercise capacity in HFpEF results from problems at multiple points along the chain of oxygen delivery: the left ventricle’s systolic reserve, the left atrium, the right side of the heart, heart rate responses, and even the ability of skeletal muscles to extract oxygen.⁹

A study that carefully mapped each step of the oxygen pathway found that peak oxygen consumption was reduced by about a third in HFpEF patients compared to matched controls. Almost all patients, 97%, had defects at more than one step. Two particular bottlenecks stood out: cardiac output (the total blood the heart pumps per minute) was about 27% lower, and the muscles’ ability to extract oxygen was about 36% lower. Interestingly, fixing the cardiac output defect alone was predicted to improve exercise capacity by only about 7%, while correcting the muscle diffusion defect predicted a 27% improvement.¹⁰ The implication is provocative: even in a heart disease, the muscles may matter more than the heart itself for daily exercise tolerance.

The Left Atrium and the Right Side of the Heart

When people think about heart failure they usually picture the left ventricle, but two neighboring structures play an outsized role in HFpEF. The left atrium, the chamber that feeds blood into the left ventricle, tends to enlarge when filling pressures chronically rise. Enlargement of the left atrium is present in the majority of HFpEF patients and is itself a marker of risk.¹¹ Once the atrium stretches beyond a certain point, atrial fibrillation becomes more likely, which further impairs heart function.

The right ventricle, which pumps blood through the lungs, is the other casualty. In a community-based study, right ventricular dysfunction was common among HFpEF patients and was linked to higher death rates and more frequent hospitalizations. After accounting for age, sex, lung artery pressure, and other conditions, the presence of right ventricular dysfunction was associated with roughly a 35% higher risk of death from any cause and an 85% higher risk of cardiovascular death.¹² The right ventricle struggles because high pressures in the left side of the heart back up into the lungs, forcing the right ventricle to pump against greater resistance. Eventually it fails to keep up.¹³

Inflammation and the Smallest Blood Vessels

A newer line of research points to the tiniest blood vessels in the heart as a driver of HFpEF. Coronary microvascular dysfunction, where the small arteries that nourish the heart muscle fail to dilate properly, has been proposed as a key mechanism linking comorbidities such as obesity and diabetes to heart muscle damage.⁵ The current theory is that systemic inflammation caused by these conditions affects the lining of the coronary microvessels, which in turn promotes stiffness and fibrosis in the surrounding heart muscle.¹⁴ If this model holds up, it would explain why HFpEF is so tightly tied to metabolic diseases and why it has been so hard to treat with drugs designed for other forms of heart failure.

How HFpEF Is Diagnosed

Diagnosing heart failure when the ejection fraction is normal is notoriously tricky. You cannot simply glance at an echocardiogram and know. The European Society of Cardiology developed a stepwise algorithm called HFA-PEFF that starts with clinical suspicion based on symptoms and risk factors, then layers in detailed echocardiographic measurements, blood tests for natriuretic peptides (hormones released when the heart is stressed), and sometimes exercise stress tests or invasive pressure measurements. A scoring system assigns points for abnormalities like elevated filling pressures, enlarged left atrium, thickened walls, and abnormal strain values. A score of five or above points toward definite HFpEF; a score of one or less makes it unlikely.¹⁵

A competing scoring system, H2FPEF, was developed from a different angle and uses a simpler set of clinical and echo variables. While both scoring systems perform reasonably well at the extremes, they disagree on a substantial number of patients. A meta-analysis found that when both algorithms are applied to the same group of patients, about 41% are classified differently by one score versus the other. The HFA-PEFF algorithm has higher specificity (roughly 90%), meaning it is better at ruling out HFpEF when it gives a low score, while the H2FPEF has slightly higher sensitivity (roughly 76%).¹⁶ This level of disagreement means that which scoring tool your cardiologist uses can genuinely change whether you receive a diagnosis. The imprecision is frustrating, but it reflects how hard it is to define a condition whose hallmark is that the most visible measurement looks normal.

Natriuretic peptide levels, the standard blood test for heart failure, add another wrinkle. They are often lower in HFpEF than in heart failure with reduced ejection fraction, and in some patients they are entirely normal. Research into alternative biomarkers, including molecules tied to inflammation and fibrosis, is ongoing but has not yet produced a widely used clinical test.¹⁷ Recent work has identified potential molecular markers that could help identify HFpEF patients whose standard blood tests come back normal, though these are still in the research phase.¹⁸

The Treatment Landscape

For decades, HFpEF was a therapeutic wasteland. Drug after drug that helped patients with reduced ejection fraction, including ACE inhibitors and beta-blockers, failed to show clear benefit in HFpEF trials. The breakthrough came with a class of drugs originally developed for diabetes called SGLT2 inhibitors. In a large randomized trial, empagliflozin reduced the combined risk of cardiovascular death or hospitalization for heart failure by about 21% compared with placebo, driven mainly by fewer hospitalizations.¹⁹ In a separate trial, dapagliflozin improved symptom scores, physical limitations, and walking distance in HFpEF patients.²⁰

Beyond SGLT2 inhibitors, treatment still leans heavily on managing the conditions that fuel HFpEF: controlling blood pressure, managing blood sugar, losing weight, and treating sleep apnea when it is present. Diuretics remain a mainstay for relieving fluid overload. The hope is that as researchers better understand the subtypes of HFpEF, more targeted therapies will follow.

Prognosis and What Drives Outcomes

People with HFpEF live longer on average than those with reduced ejection fraction, but this comparison can be misleading. After adjusting for age, sex, and clinical risk factors, one international study found that HFpEF patients had about a 38% lower risk of death than those with reduced ejection fraction.²¹ That sounds encouraging until you look at absolute numbers. In a long-term follow-up study, roughly two thirds of HFpEF patients died over a median of about five years, with cardiovascular and non-cardiovascular causes splitting almost evenly.²² The high rate of non-cardiovascular deaths reflects the heavy burden of other diseases like kidney failure, cancer, and infections in this population. HFpEF is not a benign condition just because the ejection fraction looks reassuring.

Not One Disease but Many

One reason HFpEF has been so hard to study and treat is that it is almost certainly not a single disease. Researchers have increasingly turned to machine learning to sort HFpEF patients into distinct subgroups based on dozens of clinical variables at once. One such analysis identified three clusters: one dominated by heavy comorbidity and abnormal heart structure, another by diastolic dysfunction with fewer comorbidities, and a third with relatively low levels of natriuretic peptides and the most favorable heart function. Each group had different long-term outcomes.²³

A similar approach in Japanese patients carved out three different groups: one defined by atherosclerosis and kidney disease, a second by atrial fibrillation in older women, and a third by younger men with thickened hearts and higher body weight.²⁴ The fact that the clusters look different across populations underscores how heterogeneous HFpEF truly is. The practical hope is that if doctors can reliably identify which subtype a patient has, they can tailor treatment accordingly rather than applying a one-size-fits-all approach to a condition that may encompass several distinct diseases sharing a single ejection-fraction cutoff.

When Preserved Systolic Function Appears in Women Versus Men

HFpEF disproportionately affects women. This is partly because women normally have slightly higher ejection fractions, so the 50% cutoff captures a wider band of disease in men. But the sex difference runs deeper than measurement artifacts. Older age, obesity, diabetes, and high blood pressure are all risk factors for HFpEF, and their clustering patterns differ between the sexes.²⁵ Women with HFpEF tend to have more concentric remodeling and stiffer ventricles, while men more often develop eccentric remodeling and right heart dysfunction. These patterns may call for different treatment strategies, though clinical trials have rarely been designed with sex-specific subgroups as a primary focus.

The diagnostic scoring systems described above also perform differently depending on the patient population. In patients with atrial fibrillation, for instance, both the HFA-PEFF and H2FPEF scores show only moderate accuracy against the gold standard of invasive pressure measurement.²⁶ Atrial fibrillation changes many of the echo and lab measurements that the scores rely on, which muddies their interpretation. For a cardiologist, this means the standard shortcuts work less well in precisely the patients who are most likely to have HFpEF, since atrial fibrillation and HFpEF frequently coexist.

Invasive Testing as the Final Arbiter

When non-invasive tests leave the diagnosis uncertain, invasive hemodynamic testing during exercise can settle the question. A thin catheter threaded into the heart measures pressures directly while the patient pedals a bicycle or walks on a treadmill. If filling pressures rise abnormally during exertion, HFpEF is confirmed even when resting measurements look normal. This approach has become the gold standard for diagnosing exertional breathlessness when other tests are inconclusive.²⁷ Many patients with HFpEF have completely normal pressures at rest; the dysfunction only unmasks itself when the heart is asked to work harder. That is why resting echocardiograms can miss the condition entirely and why exercise-provoked testing has become so valuable in ambiguous cases.