The heart operates in a two-phase cycle: systole (contraction) and diastole (relaxation). During systole, the heart muscle actively squeezes to pump blood out to the body. During diastole, the heart muscle relaxes, allowing the chambers to fill with blood for the next beat.
Diastolic dysfunction is a functional abnormality that affects the heart’s ability to relax. Heart failure (HF), conversely, is a clinical syndrome defined by the resulting symptoms. This distinction means that a mechanical issue like diastolic dysfunction can exist without the patient experiencing the full symptoms of heart failure.
Understanding Diastolic Dysfunction
Diastolic dysfunction describes a mechanical failure during the relaxation phase of the heart cycle. This condition primarily involves the ventricles, the heart’s main pumping chambers, losing their normal flexibility. The heart muscle becomes stiff, and its ability to relax fully is impaired, similar to trying to inflate a stiff balloon.
Because the ventricles cannot relax properly, they resist the incoming flow of blood from the atria. This resistance causes an abnormal increase in pressure inside the heart chambers. This elevated pressure then backs up into the atria and the veins returning blood to the heart, which is a significant factor leading to congestion symptoms. The impairment means the ventricle struggles to accept its normal volume of blood without a large pressure increase, forcing the heart to rely on higher pressures to fill the chamber.
Defining Heart Failure and Its Categories
Heart failure (HF) is a complex clinical syndrome where the heart is unable to pump enough blood to meet the body’s metabolic demands. This inability leads to a range of symptoms, including shortness of breath, fatigue, and fluid retention, which are signs of congestion in the lungs or other tissues. HF is a symptomatic condition that develops when the structural or functional impairment of the heart becomes severe enough to affect daily life.
The condition is functionally classified based on the heart’s pumping efficiency, which is measured by the Left Ventricular Ejection Fraction (LVEF). Ejection fraction is the percentage of blood in the left ventricle that is pumped out with each contraction, with a normal range typically being 50% to 70%. The two primary categories of heart failure are defined by this measurement.
Heart Failure with Reduced Ejection Fraction (HFrEF) is characterized by a weakened heart muscle resulting in an LVEF of 40% or lower. This form is often referred to as systolic heart failure. Conversely, Heart Failure with Preserved Ejection Fraction (HFpEF) is diagnosed when the LVEF remains 50% or greater. A third category, Heart Failure with Mid-Range or Mildly Reduced Ejection Fraction (HFmrEF), is used for LVEF values between 41% and 49%.
Diastolic Dysfunction as the Mechanism of Heart Failure with Preserved Ejection Fraction
The mechanical issue of diastolic dysfunction is the fundamental mechanism driving the clinical syndrome known as Heart Failure with Preserved Ejection Fraction (HFpEF). Diastolic dysfunction becomes HFpEF when ventricular stiffening progresses to a point where it causes symptoms of heart failure. In essence, diastolic dysfunction is the underlying cause, and HFpEF is the resulting disease state defined by symptoms and clinical signs.
While a patient can have diastolic dysfunction without experiencing any symptoms, the onset of fatigue, shortness of breath, or fluid retention indicates that the dysfunction has led to HFpEF. The elevated pressure caused by the stiff ventricle leads to congestion in the lungs and body, which is the physical manifestation of HFpEF. The key difference is that HFpEF requires both evidence of diastolic dysfunction and the presence of heart failure symptoms.
Approximately half of all heart failure cases are classified as HFpEF, highlighting the significance of this diastolic failure mechanism. The heart is still able to pump an adequate percentage of blood out with each beat, which explains the preserved ejection fraction. However, the impaired relaxation prevents the chambers from filling efficiently, particularly during periods of stress or exertion, leading to the characteristic symptoms.
Identifying and Managing the Condition
The identification of diastolic dysfunction and the diagnosis of HFpEF rely heavily on non-invasive imaging techniques. Echocardiography, a form of heart ultrasound, is the preferred method for assessing both the heart’s structure and its function. This test measures the LVEF to determine the heart failure category, but more importantly, it provides detailed information about ventricular filling.
Echocardiography evaluates specific parameters, such as the velocity of blood flow into the ventricle and the movement of the heart muscle tissue, to estimate left ventricular filling pressures. Key measurements like the E/e’ ratio help clinicians confirm the presence and severity of diastolic dysfunction. In some cases, a diagnosis may require invasive testing, such as a right heart catheterization, to directly measure filling pressures.
Management of diastolic dysfunction and HFpEF focuses primarily on treating the underlying conditions that contribute to the heart muscle stiffness. High blood pressure (hypertension) and diabetes are common risk factors that must be aggressively managed with medication and lifestyle changes. Lifestyle modifications, including regular exercise and weight loss, can also improve diastolic function and alleviate symptoms. Diuretics are often used to manage the fluid buildup and congestion symptoms that define the clinical syndrome of HFpEF.