Echocardiography Report Interpretation

1. The Anatomy of an Echocardiography Report

A standard echocardiography report is dense with abbreviations and measurements. To begin, let's get a systematic overview of its typical components.

A typical report integrates findings from different echo modalities:

• 2D (Two-Dimensional) Imaging: Provides structural information—like a series of cross-sectional pictures. This is where we measure chamber sizes and wall thickness.
• Doppler Imaging (Pulsed-Wave, Continuous-Wave, and Color): Measures the velocity and direction of blood flow. This is essential for assessing valve function and estimating pressures within the heart.

Here are some of the most common parameters and their normal ranges. Many of these were mentioned in the video.

2. Assessing Systolic Function: The Ejection Fraction

The single most scrutinized value in many echo reports is the Left Ventricular Ejection Fraction (LVEF). It is the cornerstone of assessing the heart's pumping ability, or systolic function.

LVEF represents the percentage of blood that is ejected from the left ventricle with each contraction.

$\text{LVEF}(\%)=\frac{\text{End-Diastolic Volume (EDV)}-\text{End-Systolic Volume (ESV)}}{\text{End-Diastolic Volume (EDV)}}\times 100$

Let's watch a short segment that explains how LVEF is presented in a report.

As the video explains, LVEF is categorized to grade LV systolic function:

• Normal LVEF: 55-70%
• Mildly Reduced LVEF: 41-50%
• Moderately Reduced LVEF: 31-40%
• Severely Reduced LVEF: ≤ 30%

A patient with heart failure and an LVEF of 35% has Heart Failure with reduced Ejection Fraction (HFrEF).

Beyond Ejection Fraction: Global Longitudinal Strain (GLS)

While LVEF is crucial, it's a somewhat crude measure of function. A more sensitive technique, Global Longitudinal Strain (GLS), measures the deformation (shortening) of the LV muscle itself. It can detect subtle systolic dysfunction even when the LVEF is still in the "normal" range. A normal GLS is typically more negative than -18% (e.g., -20%). This is an advanced parameter but important for a complete understanding.

3. Assessing Valvular Function: Stenosis and Gradients

Echocardiography is the primary tool for diagnosing and quantifying valvular heart disease. The two main types of valve problems are:

• Stenosis: The valve doesn't open fully, obstructing forward blood flow.
• Regurgitation (or Insufficiency): The valve doesn't close properly, allowing blood to leak backward.

Doppler echo allows us to measure the velocity of blood flowing across a valve. Using the simplified Bernoulli equation ($\Delta P=4v^2$), we can convert this velocity ($v$) into a pressure gradient ($\Delta P$). This pressure gradient tells us how severe the stenosis is.

Key takeaways on valvular assessment:

• Stenosis: Quantified using mean pressure gradients (MPG) and valve area. Higher gradients mean more severe stenosis. For example, a high MPG across the aortic valve indicates significant aortic stenosis.
• Regurgitation: Typically graded visually using color Doppler as trivial, mild, moderate, or severe. Severe regurgitation means a large volume of blood is leaking backward, increasing volume load on the heart chambers.

4. A Deep Dive into Diastolic Function

This is arguably the most complex part of echo interpretation, but it's critically important. Many patients with symptoms of heart failure have a normal LVEF. Their problem isn't pumping (systole) but rather filling (diastole). This is Heart Failure with preserved Ejection Fraction (HFpEF).

Diastolic dysfunction means the left ventricle is stiff and cannot relax properly to accommodate blood during the filling phase. This causes a backup of pressure into the left atrium and, subsequently, the lungs, leading to dyspnea.

To understand diastolic function, we must first understand the phases of normal diastolic filling.

The Four Key Parameters for Assessing Diastolic Function

The 2016 guidelines from the American Society of Echocardiography (ASE) recommend an algorithmic approach using four key variables.

1. Annular e' velocity: Measured with Tissue Doppler, the e' (e-prime) velocity reflects the speed at which the mitral annulus (the base of the heart) moves during early diastole. A slow e' indicates poor LV relaxation.

   • Abnormal: Septal e' < 7 cm/s or Lateral e' < 10 cm/s.

2. Average E/e' ratio: This is the ratio of the mitral inflow E-wave velocity (reflecting the pressure gradient from the LA to the LV) to the annular e' velocity (reflecting LV relaxation). It is a powerful, non-invasive estimate of LV filling pressure (Left Atrial Pressure - LAP).

   • Abnormal (suggests high filling pressure): Average E/e' > 14.

3. Left Atrial Volume Index (LAVI): The left atrium dilates in response to chronically elevated filling pressures. A large LA is therefore a marker of chronic diastolic dysfunction.

   • Abnormal: LAVI > 34 mL/m².

4. Peak Tricuspid Regurgitation (TR) velocity: A high velocity of the TR jet reflects high pressure in the right ventricle, which is often a consequence of high pressure on the left side of the heart (pulmonary hypertension secondary to elevated LAP).

   • Abnormal: Peak TR velocity > 2.8 m/s.

The Algorithm for Grading Diastolic Dysfunction

Now, let's put it all together. The following algorithm is used for patients with known myocardial disease or those with normal LVEF who are being evaluated for diastolic dysfunction.

Here is how to use the algorithm:

1. Examine the Mitral Inflow Pattern (E/A ratio):

   • If E/A ≤ 0.8 AND the peak E wave velocity is ≤ 50 cm/s, this indicates impaired relaxation. This is Grade 1 Diastolic Dysfunction (normal filling pressures).
   • If E/A ratio is > 2, this is a restrictive filling pattern. This is Grade 3 Diastolic Dysfunction (high filling pressures).

2. Apply the Four Parameters:

   • For cases that don't fit the above patterns (e.g., E/A is between 0.8 and 2), you must check the four key parameters (annular e', E/e' ratio, LAVI, TR velocity).
   • If more than half of the available parameters are abnormal, you can conclude that LA pressure is elevated.
   • If less than half are abnormal, LA pressure is normal.
   • If exactly half are abnormal, the status is indeterminate.

This leads to the following grades:

• Normal Function: Normal relaxation and normal filling pressures.
• Grade 1 (Impaired Relaxation): The LV relaxes slowly, but filling pressures are normal at rest. The A-wave becomes dominant (E/A < 0.8).
• Grade 2 (Pseudonormal): LV relaxation is still poor, but now filling pressures are elevated to compensate. This makes the E/A ratio look normal (0.8-2.0), which is why we need the other four parameters to unmask the problem.
• Grade 3 (Restrictive Filling): The LV is very stiff, and filling pressures are high. Early filling is rapid and abrupt due to high LA pressure, leading to a very tall E wave (E/A > 2). This pattern is associated with a poor prognosis.

Conclusion

Excellent work. We've navigated the essentials of an echocardiography report, moving from basic structural measurements to the nuanced assessment of systolic and diastolic performance. This is a dense topic, but one that is fundamental to clinical cardiology.

Key Takeaways:

• Systematic Review: An echo report combines 2D structural data (chamber sizes, wall thickness) with Doppler flow data (velocities, gradients).
• Systolic Function: LVEF is the primary measure, with values <55% indicating some degree of systolic dysfunction (HFrEF).
• Valvular Function: Stenosis severity is quantified by pressure gradients derived from Doppler velocities ($\Delta P=4v^2$). Regurgitation is graded by the amount of backward leakage.
• Diastolic Function: Essential for diagnosing HFpEF. Its assessment involves a multi-parameter algorithm including the E/A ratio, E/e' ratio, LAVI, and TR velocity to grade dysfunction and estimate filling pressures.

You can now appreciate how an echo report confirms the suspicions raised by an ECG or CXR. The LVH on an ECG and cardiomegaly on a CXR are visualized and measured on echo. The signs of pulmonary venous hypertension on a CXR are explained by the finding of elevated filling pressures (high E/e' ratio) on echo.

In our next lesson, we will synthesize what you've learned about ECGs, CXRs, and now echocardiography. We will begin to apply diagnostic algorithms for the evaluation of common cardiac presentations like chest pain, dyspnea, and palpitations, using these tools to arrive at a diagnosis.