The heart is a muscular pump that continuously circulates blood throughout the body, delivering oxygen and nutrients to every cell. This intricate process involves two main phases: systole, when the heart contracts to push blood out, and diastole, when it relaxes to fill with blood. Maintaining proper heart function during both phases is fundamental for cardiovascular health, as disruption impacts blood flow. Diastolic dysfunction is a condition that specifically affects the heart’s relaxation and filling abilities, a significant concern in cardiovascular medicine.
What is Diastolic Dysfunction?
The heart’s ability to relax and fill with blood is known as diastole, the relaxation phase. During this period, the lower chambers of the heart, called the ventricles, should relax and expand to receive blood from the atria. When diastolic dysfunction occurs, the ventricles become stiff or less flexible, hindering their ability to relax properly. This stiffness prevents complete filling, reducing the blood available for the next pump.
Incomplete filling increases pressure within the heart’s chambers, particularly the left atrium. This elevated pressure can cause blood to back up into the lungs and other organs, impacting their function. Think of it like a rigid balloon that is difficult to inflate; it cannot hold as much air, and the pressure inside builds up quickly, affecting the flow of air into it. Over time, this sustained pressure can progress, potentially leading to heart failure where the heart pumps normally but struggles to fill.
How Echocardiography Helps Diagnose Diastolic Dysfunction
Echocardiography is a non-invasive imaging technique that uses sound waves to create live images of your heart. It allows visualization of the heart’s structure, including chamber size, wall thickness, and valve movement. This real-time visualization assesses the heart’s pumping and relaxation functions.
Echocardiography diagnoses diastolic dysfunction by analyzing blood flow patterns and pressures within the heart. By observing blood movement into the ventricles during relaxation, doctors identify filling abnormalities. It assesses how well the heart muscle relaxes and stretches, directly related to adequate filling. It provides a comprehensive view of the heart’s mechanics, making it the primary tool for evaluating diastolic function.
Interpreting Echocardiogram Findings
Interpreting echocardiogram findings for diastolic dysfunction involves assessing parameters that provide insights into the heart’s filling pressures and relaxation. One parameter is the E/A ratio, comparing the velocity of early diastolic filling (E wave) to late diastolic filling caused by atrial contraction (A wave). In normal hearts, the E wave is larger than the A wave, indicating efficient early filling. In mild diastolic dysfunction, the E wave may decrease, and the A wave may increase, resulting in an E/A ratio less than 0.8.
Another measurement is the E/e’ ratio, relating the early mitral inflow velocity (E) to the early diastolic mitral annular tissue velocity (e’). The e’ velocity, measured by tissue Doppler imaging, reflects the heart muscle’s ability to relax. A reduced e’ velocity (less than 7 cm/s for the septal wall or 10 cm/s for the lateral wall) suggests impaired relaxation. An elevated E/e’ ratio (greater than 14) indicates increased left ventricular filling pressures, a hallmark of more advanced diastolic dysfunction.
The left atrial volume index (LAVI) is also considered; an enlarged left atrium (LAVI greater than 34 mL/m²) suggests chronically elevated left atrial pressures due to impaired ventricular filling. Additionally, the peak tricuspid regurgitation (TR) velocity, if present, can help estimate pulmonary artery systolic pressure; a velocity greater than 2.8 m/s suggests elevated pressures associated with diastolic dysfunction. These parameters collectively help classify the severity of diastolic dysfunction into grades.
Diastolic dysfunction is commonly graded based on these findings:
Grade I: Impaired Relaxation
This grade is characterized by an E/A ratio less than 0.8 and a reduced e’ velocity, signifying a stiff ventricle that takes longer to relax.
Grade II: Pseudonormal Filling
This occurs when left atrial pressure increases, normalizing the E/A ratio to between 0.8 and 2, but the e’ velocity remains low (less than 8 cm/s). This “pseudonormal” appearance means the heart is compensating for its stiffness.
Grade III: Restrictive Filling
This is the most severe stage, marked by a significantly elevated E/A ratio (greater than 2) and a very short deceleration time of the E wave, along with a significantly reduced e’ velocity. This indicates severely elevated left atrial pressures and a very stiff ventricle, leading to rapid, but often incomplete, early filling.
Understanding the Implications of Diastolic Dysfunction
Diastolic dysfunction has implications for health, often stemming from underlying conditions. Aging is a common factor; over half of adults aged 70 and older are estimated to have some degree of diastolic dysfunction. Other common causes and risk factors include high blood pressure (hypertension), diabetes, obesity, coronary artery disease, and heart attacks. These conditions contribute to heart muscle stiffening over time.
Individuals with diastolic dysfunction may experience symptoms such as shortness of breath (particularly with physical activity) and increased fatigue. These symptoms arise because the heart’s inability to fill properly causes blood to back up, leading to fluid accumulation in the lungs and shortness of breath. Fluid retention can also occur in the lower extremities or abdomen, leading to swelling (edema).
While mild diastolic dysfunction might not cause noticeable symptoms initially, it tends to progress. If left unmanaged, the condition can advance to diastolic heart failure, also known as heart failure with preserved ejection fraction (HFpEF), where the heart pumps normally but cannot fill adequately. Early diagnosis is important for managing underlying conditions, which can help prevent further progression and complications.