Diastolic dysfunction (DD) is a condition where the heart’s main pumping chamber, the left ventricle, has difficulty relaxing fully between beats (diastole). During this relaxation phase, the ventricle is supposed to fill with blood returning from the lungs. The issue is not the heart’s ability to contract (systole), but rather its inability to properly loosen and expand to accommodate the incoming blood volume. This impaired relaxation prevents the left ventricle from filling efficiently or completely. Consequently, less blood is available to be pumped out to the body during the next beat. Over time, this mechanical failure can progress and lead to heart failure with preserved ejection fraction (HFpEF).
Understanding Diastole and the Failure to Fill
The cardiac cycle includes systole (contraction and pumping) and diastole (relaxation and filling). During normal diastole, the left ventricle actively relaxes, creating a suction effect that draws blood from the left atrium. This allows the heart muscle fibers to lengthen and the chamber to fully expand, ensuring maximum blood intake.
Diastolic dysfunction disrupts this process because the left ventricular walls become abnormally stiff and less compliant. The ventricle resists expansion, similar to a stiff balloon, which impairs its ability to fill with blood.
Since the ventricle cannot expand easily, a higher pressure is required to force blood inside. This increased pressure is transmitted backward, first into the left atrium and then into the veins and capillaries of the lungs. The resulting pressure elevation in the pulmonary circulation forces fluid out of the blood vessels and into the lung tissue.
This fluid backup is the core mechanism leading to symptoms. Although the heart’s pumping ability (ejection fraction) may be preserved, the fundamental issue is the failure to receive the necessary volume of blood. This stiffening results from structural changes in the heart muscle, such as the accumulation of fibrous tissue and myocyte hypertrophy, which reduces elasticity.
Common Causes and Contributing Factors
The underlying causes of diastolic dysfunction are chronic medical conditions that place persistent stress on the heart muscle. Chronic, uncontrolled high blood pressure (hypertension) is the most common factor. The heart must constantly pump against elevated arterial pressure, causing the left ventricle muscle to thicken (hypertrophy) to generate more force.
This long-term thickening and overwork cause the muscle to become rigid and less able to relax. Other chronic conditions, such as diabetes mellitus, also contribute to stiffening through mechanisms like the glycosylation of muscle proteins, reducing elasticity.
Coronary artery disease, which reduces blood flow, can cause localized stiffness due to scarring. Advancing age is another factor, as the heart and blood vessels naturally lose elasticity, increasing the risk of DD. Obesity further contributes by promoting systemic inflammation and metabolic changes that negatively impact heart structure.
Recognizing the Symptoms
The symptoms of diastolic dysfunction result from backward pressure and fluid accumulation caused by the heart’s inability to fill completely. Shortness of breath (dyspnea) is a main complaint, occurring initially during physical exertion and progressing to minimal activity or rest as the condition worsens.
Many individuals also experience orthopnea, which is difficulty breathing when lying flat. This occurs because reclining shifts fluid from the lower extremities into the central circulation, overwhelming the heart’s impaired capacity. Fluid congestion in the lungs often leads to a persistent cough or wheezing.
Excessive fatigue is common, resulting from the body’s tissues not receiving an adequate supply of oxygenated blood due to inefficient filling. Swelling, or peripheral edema, typically in the legs, ankles, and feet, is also observed as elevated pressures back up into the systemic circulation.
Diagnosis and Severity Grading
Diagnosis of diastolic dysfunction is confirmed using an echocardiogram, a non-invasive ultrasound of the heart. This test allows physicians to visualize the heart’s structure and measure the speed and pattern of blood flow entering the left ventricle. These flow measurements, obtained using Doppler technology, are essential for determining the presence and severity of relaxation impairment.
A central component of this assessment is the measurement of the E/A ratio, which compares the velocity of early (E wave) and late (A wave) filling of the ventricle.
Grade I (Mild)
In the mildest form, Grade I diastolic dysfunction, the E/A ratio is less than one. This indicates impaired relaxation but often with normal filling pressures. This early stage is frequently asymptomatic.
Grade II (Moderate)
Grade II dysfunction is referred to as a “pseudonormalized” filling pattern. The E/A ratio may appear normal, but this occurs because the left atrial pressure has increased to compensate for the stiff ventricle.
Grade III (Severe)
The most severe form, Grade III, is known as a restrictive filling pattern. It shows a significantly elevated E/A ratio and a very short deceleration time. This stage is associated with severely elevated filling pressures and pronounced symptoms of heart failure.
Management Strategies
Management of diastolic dysfunction focuses on two main objectives: treating the underlying medical conditions that caused the heart to stiffen and controlling fluid volume to alleviate symptoms. Addressing the root cause, such as aggressive control of chronic hypertension or managing blood sugar in diabetes, is the most effective long-term strategy.
Medications like angiotensin-converting enzyme (ACE) inhibitors or angiotensin receptor blockers (ARBs) are prescribed to manage blood pressure and prevent further cardiac remodeling. Diuretics are used to manage fluid buildup, reducing congestion in the lungs and swelling. These medications help the body excrete excess water and salt, lowering circulatory pressure and easing dyspnea.
Beta-blockers or calcium channel blockers may also be used to slow the heart rate. This allows more time for the stiffened ventricle to fill during diastole. Lifestyle modifications are also crucial, including a low-sodium diet to control fluid retention and regular, moderate exercise to improve cardiovascular health.