10 Echocardiography in the Patient with Right Heart Failure
Basic Principles of Right Ventricular Imaging
Step-by-Step Approach
Step 1: Analysis of Right Ventricular Size
Key Points
• Obtain two-dimensional (2D) images utilizing parasternal, right ventricular (RV) inflow, apical 4-chamber, and subcostal views.
• The RV has a crescent shape, with no accurate geometric representation.
Figure 10-1 Schematic from the apical view of a normal heart showing measurement of RV basal, midcavity, and longitudinal dimensions (arrows).
(Courtesy of Ted Plappert.)
Step 2: Analysis of RV Volume and Systolic Function
Key Points
• For volume measurements using area-length and Simpson’s rule, assumptions of geometric shape are necessary and may not be accurate.
• Estimate RV systolic function qualitatively: normal, mildly reduced, moderately reduced, or severely reduced
• Estimate RV systolic function quantitatively using a combination of the following methods.
• Right ventricular fractional area change (RVFAC) can be calculated using the following formula:
Using the apical 4-chamber view with focus on the RV, trace the RV volume from the tricuspid annulus down the free wall to the apex and back along the septum; tricuspid leaflets, trabeculations, and chords are regarded as cavity. RVFAC = 35% is the lower limit of normal in reference studies.
• On RV tissue Doppler, normal pulsed wave Doppler peak velocity at the tricuspid annulus is greater than 10 cm/s.
• Tricuspid annular plane systolic excursion (TAPSE) can be calculated from the apical 4-chamber view using M-mode and 2D techniques (see “Measurement of Prognostic Echocardiographic Parameters” below).
• Radionuclide ventriculography has been utilized historically for comparison with newer methods. However, due to the unique shape of the RV, three-dimensional (3D) echocardiography and cardiac magnetic resonance imaging (MRI) are best suited for accurate assessments of volume and systolic function (RV ejection fraction [RVEF]). These methods can be time consuming and are not widely available.
Step 3: Evaluation of RV Wall Motion
Key Points
• Septal and free wall motion should be assessed in multiple 2D views, including parasternal short-axis, apical 4-chamber, and subcostal views.
• RV volume and/or pressure overload can cause septal wall motion abnormality.
• Pressure overload of the RV causes flattening of the interventricular septum as a result of an abnormal pressure gradient between the RV and the LV, in essence pushing the septum toward the LV during both in systole and in diastole (Figure 10-3). Normally, when viewed in the parasternal short axis, the LV has the appearance of a symmetrical O or “doughnut.” With RV pressure or volume overload, the septum is D-shaped.
• Volume overload of the RV results in flattening of the interventricular septum during diastole only.
• Free wall motion should be assessed for regional wall motion abnormalities suggestive of RV infarction versus global wall motion abnormality.
Figure 10-3 2D echocardiogram from the parasternal short-axis view of the interventricular septum in a normal heart (top panels) and the heart from a patient with RV volume and pressure overload (bottom panels) during diastole (left panels) and systole (right panels). Note the D-shaped LV in the bottom panels, illustrating shift of the septum toward the LV.
Identify the Cause of Right Heart Failure
RV Infarction
• RV infarction is relatively rare. The vast majority of RV infarctions occur in the setting of acute inferior myocardial infarction.
• Obtaining right-sided electrocardiographic (ECG) leads in acute inferior myocardial infarction often helps in making the diagnosis.
• The characteristic hemodynamic sensitivity to alterations in preload is a hallmark of RV infarction and impacts upon treatment strategies.
Step-by-Step Approach
Step 1: Assess LV Wall Motion and Systolic Function, and Look for Mechanical Complications of Myocardial Infarction
Pulmonary Arterial Hypertension
• There are many etiologies of secondary pulmonary hypertension (Box 10-1). When pulmonary hypertension is suspected, a detailed search for an underlying cause should be performed. This section refers specifically to the evaluation of pulmonary arterial hypertension.
• Chronic pressure overload of the RV resulting from high pulmonary vascular resistance (PVR) results in pulmonary hypertension.
• There are echocardiographic signs of pulmonary hypertension that can be helpful in making the diagnosis and assessing disease progression and response to treatment.
• Echocardiography can be used to estimate PASP, pulmonary artery diastolic pressure (PADP), and PVR noninvasively (see “Measurement of Prognostic Echocardiographic Parameters” below).
Step-by-Step Approach
Step 1: Assess RV Size and Function
Key Points
• RV function is often preserved or hyperdynamic during this phase of disease and can be assessed using TAPSE and qualitative estimation.
Step 2: Look for Associated Right Heart Findings of Pulmonary Hypertension
Key Points
• Doppler velocity curve of the RV outflow tract (RVOT)/PA has mid-systolic “notching” (Figure 10-6).
• The main PA may be enlarged (>2.5 cm) and should be measured from the left parasternal acoustic window if 2D image quality permits.
• There are septal wall motion abnormalities suggestive of RV pressure overload (described earlier in “Basic Principles of Right Ventricular Imaging”).
• In cases of severe pulmonary hypertension and RA enlargement, stretching of the foramen ovale may result in a right-to-left shunt.
• In advanced cases of PA hypertension, a pericardial effusion can be seen. Because of elevated RV pressure and hypertrophy, frank tamponade rarely occurs.
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