Heart failure (HF) is a medical syndrome where the heart cannot pump enough blood to meet the body’s needs, often resulting in fatigue, shortness of breath, and fluid retention. HF is classified into categories based on the specific mechanical problem within the heart, which is a distinction that directly influences the course of treatment. Understanding the difference between systolic and diastolic heart failure is fundamental to effective management and better patient outcomes.
Defining the Mechanical Difference
The core difference between the two types of heart failure lies in whether the problem affects the heart’s squeezing function or its filling function. Systolic heart failure, also known as Heart failure with reduced Ejection Fraction (HFrEF), is fundamentally a problem with the heart’s ability to pump blood out to the body. The main pumping chamber, the left ventricle, becomes weakened and enlarged, unable to contract with sufficient force to eject an adequate volume of blood. This functional failure can be likened to a weak, over-stretched pump that cannot generate enough pressure to move fluid effectively.
Diastolic heart failure, or Heart failure with preserved Ejection Fraction (HFpEF), presents a problem during the relaxation and filling phase between heartbeats. In this condition, the heart muscle becomes stiff and often thickened, which prevents the left ventricle from fully relaxing and expanding to fill with blood. While the muscle may still squeeze with adequate strength, the reduced space and inability to relax means the ventricle holds less blood overall.
Distinct Causes and Contributing Factors
Systolic heart failure is primarily the result of direct damage to the heart muscle, leading to its weakening and dilation. The most common causes include a past heart attack (myocardial infarction), which results in scar tissue that cannot contract, and long-standing coronary artery disease that restricts blood flow to the heart muscle. Other factors, such as viral infections leading to inflammation of the heart muscle (myocarditis) or genetic predispositions, can also result in a significantly reduced pumping function.
Diastolic heart failure is most frequently caused by chronic conditions that increase the heart’s workload and lead to structural changes over time. Uncontrolled, long-term high blood pressure (hypertension) is a major contributor, as the heart must pump against consistently high resistance, causing the muscle to thicken and stiffen. Lifestyle diseases like obesity and diabetes are also increasingly recognized as contributing factors to HFpEF, often through mechanisms involving systemic inflammation and changes in the heart muscle’s cellular environment. Advancing age is another factor, as the heart naturally becomes less elastic over time, increasing the risk of impaired relaxation.
How Doctors Distinguish the Two Types
Distinguishing between systolic and diastolic heart failure involves measuring the heart’s pumping efficiency using the Ejection Fraction (EF). Ejection Fraction is the percentage of blood in the left ventricle that is pumped out with each contraction. A transthoracic echocardiogram, or “echo,” is the primary non-invasive imaging tool used to obtain this measurement, providing a direct visualization of the heart’s structure and function.
In systolic heart failure (HFrEF), the Ejection Fraction is significantly reduced, typically measured at 40% or lower, confirming the heart’s inability to squeeze effectively. Conversely, a diagnosis of diastolic heart failure (HFpEF) requires the Ejection Fraction to be preserved, generally 50% or higher, indicating the squeezing power is relatively intact. The diagnosis of HFpEF is then confirmed by additional echocardiographic evidence of impaired relaxation or stiffness of the ventricle. Symptoms like shortness of breath and fatigue are often similar in both conditions, making the Ejection Fraction measurement a necessary clinical step to determine the specific mechanical issue.
Specific Treatment Strategies
Effective treatment for heart failure must be tailored to address the mechanical failure identified by the Ejection Fraction. For systolic heart failure (HFrEF), the goal of treatment is to reduce the heart’s workload and improve its pumping ability. This is achieved through medication classes that target the body’s neurohormonal systems, including:
- Angiotensin-Converting Enzyme (ACE) inhibitors
- Beta-blockers
- Mineralocorticoid Receptor Antagonists (MRAs)
Newer medications, such as Angiotensin Receptor-Neprilysin Inhibitors (ARNIs) and Sodium-Glucose Cotransporter-2 (SGLT2) inhibitors, have also demonstrated substantial benefits in reducing hospitalizations and improving outcomes for patients with HFrEF.
Treatment for diastolic heart failure (HFpEF) focuses heavily on managing the underlying conditions that caused the heart to stiffen, such as aggressively controlling high blood pressure and diabetes. Diuretics are commonly used to manage fluid retention and congestion, which helps to alleviate symptoms like swelling and shortness of breath. The SGLT2 inhibitor class is the first group of medications to demonstrate a clear reduction in heart failure hospitalizations across the full spectrum of Ejection Fraction, including HFpEF. Pharmacological options for HFpEF have historically been less specific than those for HFrEF, making the management of co-existing conditions, along with fluid control, particularly important.