• 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).

Box 10-1 Etiologies of Pulmonary Hypertension

• Diseases that cause elevated pulmonary venous pressure

• Acute and chronic pulmonary embolism

• Intrinsic lung disease

• Disorders that cause intracardiac shunting

• Primary pulmonary hypertension

Step-by-Step Approach

Step 1: Assess RV Size and Function

Key Points

• The RV initially enlarges and hypertrophies as a compensatory response to pressure overload.

• RV function is often preserved or hyperdynamic during this phase of disease and can be assessed using TAPSE and qualitative estimation.

• With progressive increase in RV afterload, the RV initially hypertrophies and then dilates and the normal tricuspid valve geometry is disrupted, resulting in tricuspid regurgitation and systolic dysfunction leading to RV failure (Figure 10-4).

Figure 10-4 2D echocardiogram from the apical 4-chamber view showing severe RV dilatation that is apex-forming and marked dysfunction typical of end-stage RV failure (left panel in diastole, right panel in systole).

Step 2: Look for Associated Right Heart Findings of Pulmonary Hypertension

Key Points

• Tricuspid regurgitation due to annular dilatation is common.

• Right atrial (RA) enlargement is often present.

• M-mode of the pulmonic valve reveals a diminished or absent a wave.

• M-mode of the pulmonic valve reveals midsystolic closure—the “flying W” sign (Figure 10-5).

• 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”).

• Left heart filling abnormalities including reduced mitral valve E/A ratio can be seen.

• 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.

• Compression of the LV with impaired filling is a poor prognostic sign (Figure 10-7).

Figure 10-5 M-mode of the pulmonic valve from the parasternal short-axis view. Note the midsystolic closure of the valve (arrow) that can be seen with significant pulmonary hypertension.

Courtesy of Amresh Raina, MD.

Figure 10-6 Pulsed wave Doppler of the RVOT in a patient with pulmonary hypertension resulting in pulmonary vascular disease. Note the midsystolic “notch” that can be observed with significant pulmonary vascular disease (arrow).

Figure 10-7 2D transthoracic echocardiogram from the parasternal long-axis view showing a compressed, underfilled LV in a patient with severe RV dilatation and dysfunction.

Step 3: Calculate PASP, PADP, and PVR

• See “Measurement of Prognostic Echocardiographic Parameters” below.

Acute Pulmonary Embolism

• Acute pulmonary embolism can cause right heart failure due to sudden increase in PVR.

• The degree of pulmonary hypertension that occurs acutely is often less severe than that which can occur over time with chronic causes of pulmonary hypertension.

• In acute pulmonary embolism, there is no time for compensatory changes. Moderate to severe elevations in PASP can be seen in association with clinically relevant right heart failure.

• Although echocardiography can be helpful in the diagnosis and treatment of acute pulmonary embolism, the standard clinical methods of diagnosis are computed tomography of the chest with intravenous contrast or radionuclide lung ventilation-perfusion scan. Only rarely is pulmonary angiography needed for diagnosis.

Step-by-Step Approach

Step 1: Assess RV Size, Shape, and Function

Key Points

• The RV is often dilated with acute systolic dysfunction.

• Septal motion reveals signs of pressure and/or volume overload.

• A classic finding is McConnell’s sign: a dilated, apex-forming RV with preserved systolic function of only the apical segment (Figure 10-8).

Figure 10-8 2D transthoracic echocardiogram from the apical 4-chamber view of the RV in the setting of acute pulmonary embolism. Note that the RV forms the apex of the heart (left panel). In this example of McConnell’s sign, there is preserved systolic function of only the apical segment of the RV (right panel).

Step 2: Look for Associated Findings That Can Accompany Acute Pulmonary Embolism

Key Points

• The RA may be normal in size due to the acute nature of the insult.

• There may be associated tricuspid regurgitation.

• Rarely, a pulmonary embolus can be visualized in the pulmonary artery from the 2D parasternal short-axis view. Color Doppler may reveal turbulent flow in the PA.

• An attempt should be made to look for thrombus in the RA and inferior vena cava (IVC).

• The LV usually functions normally or is underfilled with hyperdynamic function.

Step 3: Calculate PA Systolic Pressure

• See “Measurement of Prognostic Echocardiographic Parameters” below.

Intracardiac Shunt

• Abnormal intracardiac communications can cause right heart dysfunction and should be looked for carefully in the evaluation of right heart enlargement and pulmonary hypertension.

• If transthoracic images do not adequately exclude intracardiac shunting, transesophageal echocardiography (TEE) should be performed.

• The volume and direction of blood flow are determined by the size of the communication, the pressure gradient between the two chambers, and the resistance to flow in the distal vascular beds.

• Atrial septal defects (ASDs) and partial anomalous pulmonary venous return can cause left-to-right shunting and chronic volume overload of the RA and RV.

• VSDs can cause left-to-right shunting. RV size may remain normal, because blood flows from the LV to the RV and almost immediately into the PA during systole.

• Rarely, a coronary artery fistula to the RV can lead to RV dilatation. Turbulent flow in the RV can be visualized with color Doppler and, if 2D imaging is optimal, a dilated coronary artery is seen.

• Over time, especially if the pulmonary-to-systemic shunt ratio exceeds 2 : 1, pulmonary pressures and PVR increase. Irreversible pulmonary hypertension and right heart failure can occur.

Step-by-Step Approach

Step 1: Assess RA and RV Size

Key Points

• With significant left-to-right shunting through an ASD or anomalous pulmonary venous return, the RA and RV should be enlarged. Right heart size is best evaluated from the apical and subcostal views.

• Normal RV size can be seen with VSD.

Step 2: Assess RV Function (described above)

Step 3: Look for Intracardiac Shunting

Key Points

• ASDs include ostium primum, ostium secundum, sinus venosus, and coronary sinus defects.

• Evaluate the interatrial septum with 2D and color Doppler in the parasternal short-axis, apical 4-chamber, and subcostal 4-chamber views to look for an ASD. Flow across the atrial septum, if present, will be of low velocity because of the small pressure gradient between the left atrium (LA) and RA.

• Identification of pulmonary vein flow into the LA can be evaluated from the apical 4-chamber view. However, in adults, it is usually not possible to visualize all four pulmonary veins. TEE should be performed to visualize pulmonary vein flow if suspicion for partial anomalous pulmonary venous return is high.

• It is often difficult to visualize a sinus venosus ASD using TTE. The suprasternal, apical, and subcostal views should be used, with the subcostal view most likely to visualize a defect. In addition, sinus venosus ASDs are usually associated with partial anomalous pulmonary venous return. TEE should be performed for adequate visualization.

• Most commonly, the right upper or middle pulmonary veins drain directly into the right atrium or into the superior vena cava.

• Evaluate the interventricular septum with 2D and color Doppler in the parasternal long-axis, parasternal short-axis, apical 4-chamber, and subcostal views to look for a VSD. Because of the large pressure gradient between the LV and RV, interventricular flow is typically high velocity. A notable exception is a large non-restrictive VSD, where pressure has equalized between the LV and RV (Eisenmenger syndrome).

• An estimate of the pressure gradient between the two chambers can be calculated using the peak velocity of the blood flow across the VSD, where ΔP = 4v². Doppler analysis should be undertaken in multiple views to optimize intercept angle.

• Shunt flow can be quantified noninvasively using the Qp/Qs ratio (see Chapter 6):

where Qp is blood flow in the pulmonary circulation, Qs is blood flow in the system circulation, VTI is the velocity-time integral, PA is the pulmonary artery, and LVOT is the left ventricular outflow tract.

• Perform agitated saline contrast injection to look for evidence of right-to-left flow across an ASD or PFO.

• The apical 4-chamber or subcostal view generally works best, keeping in mind that recording should continue for several seconds to ascertain timing of flow.

• Often, multiple injections of agitated saline are needed, during normal respiration, cough, and/or Valsalva maneuver.

• If late passage of contrast (after 5 beats) is observed, this suggests the presence of pulmonary arteriovenous malformations rather than an ASD or PFO.

Step 4: Calculate PASP, PADP, and PVR

• See “Measurement of Prognostic Echocardiographic Parameters” below.

Right-Sided Valvular Disease

• Primary tricuspid and pulmonary valve disease can cause secondary right heart abnormalities. These entities should be included in the differential diagnosis of right heart failure.

Cardiomyopathy Affecting the RV

• When evaluating potential primary causes of right heart dysfunction, nonischemic dilated cardiomyopathy, arrhythmogenic RV cardiomyopathy (ARVC), infiltrative disease, and restrictive cardiomyopathy should be in the differential diagnosis.

• Classic findings of ARVC on echocardiography include an enlarged and dysfunctional RV with focal wall motion abnormalities and free wall aneurysms (Figure 10-9). Adipose and fibrous tissue infiltration of the RV free wall is seen on pathology. In a minority of ARVC cases, the LV is also affected. If echocardiography is not conclusive, cardiac MRI can be helpful in establishing the diagnosis noninvasively.

• Infiltrative disease, including hemochromatosis and amyloid, can affect both ventricles.

Figure 10-9 2D transthoracic echocardiogram from the apical view of the RV in ARVC. Note that the RV is severely enlarged and deformed with focal aneurysm (asterisk). Fibro-fatty infiltration of the free wall can be seen with MRI. Patients often present with abnormal ECG and ventricular arrhythmias.

Measurement of Prognostic Echocardiographic Parameters

PA Systolic Pressure

• PASP can be calculated noninvasively using echocardiography.

• Two components are needed to calculate PASP.

• The first is the pressure gradient between the RV and RA, which is ascertained by measuring the peak velocity of the tricuspid regurgitation jet (V_TR).

• The second is an estimate of RA pressure (RAP), described below.

Step-by-Step Approach

Step 1: Record Maximum V_TR

Key Points

• Using 2D and color-guided continuous wave Doppler in multiple views, find the maximum V_TR (Figure 10-10).

• Care should be taken to obtain a parallel intercept angle between the regurgitation jet and the ultrasound beam.

Figure 10-10 Continuous wave Doppler of the tricuspid regurgitation jet. Maximum V_TR should be measured (arrow) in multiple views to calculate PASP.

Step 2: Estimate RAP Noninvasively

Key Points

• RA pressure can be estimated from the degree of collapse of the IVC during inspiration.

• Using 2D from the subcostal window, measure the diameter of the IVC (Figure 10-11).

• Using 2D and M-mode, estimate the degree of IVC collapse during inspiration (Figure 10-12).

• Estimate the RAP from IVC collapse (Table 10-1). The simplest method of estimating RAP is to look at the degree of inspiratory IVC collapse alone. More sophisticated estimates include IVC size, RA size, and degree of tricuspid regurgitation.