Parasternal View Saddle Embolus Echocardiogram

Fig. 2. A higher magnification of the parasternal short axis view at the aortic valve level of the patient with the pulmonary saddle embolus (arrow) described in Fig. 1. (Please see companion DVD for corresponding video.)

and indirect evidence of the diagnosis in patients with pulmonary embolus (Table 1).

Thrombi can be visualized within the venous system from the inferior vena cava, through the right atrium, the RV, the right ventricular outflow tract, and the pulmonary arteries until just distal to the pulmonary bifurcation. The direct visualization of thrombus in the pulmonary artery confirms the presence of a PE, but this finding is not usually seen on TTE. If a thrombus is visualized by TTE, it is usually limited to the right heart, the main pulmonary artery, or the bifurcation of the right and left pulmonary arteries (Figs. 1 and 2; please see companion DVD for corresponding video). Using TTE in the International Cooperative Pulmonary Embolism Registry (ICOPER) registry, intracardiac thrombi was visualized in approx 4% of patients with acute PE. In patients with a massive pulmonary embo-lus, the frequency of intracardiac thrombus may be increased. When intracardiac thrombus is visualized, it is most commonly visualized in the right atrium and often appears worm-like, although a small percentage is described as spherical in appearance. The differential

Table 1

Echocardiography Signs of Pulmonary Embolism

Two-dimensional echo

Direct visualization of thrombus in the right heart or pulmonary artery

Right ventricular hypokinesis

Right ventricular enlargement

Reduced left ventricular size

McConnell's sign

Flattening of the intraventricular septum or paradoxical septal motion

Dilated pulmonary artery

Dilated right atrium

Distension of the inferior vena cava with loss of normal respiratory variation

Doppler

Increased peak velocity of tricuspid valve insufficiency

Shortened pulmonary ejection acceleration time (<80 ms)

Parasternal Long Axis

Fig. 3. Parasternal long axis view of a patient with acute pulmonary embolism demonstrates an enlarged, hypokinetic right ventricle (RV) with leftward displacement of the intraventricular septum (arrows). Left ventricular (LV) systolic function appears small, underfilled, and hyperdynamic. These are findings of severe RV dysfunction in the setting of acute pulmonary embolism.

Hyperdynamic Left Ventricular Function

Parasternal short axis

Fig. 4. Parasternal short-axis view of the left ventricle from patient in Fig. 3 demonstrates a severely enlarged right ventricle with intraventricular septal flattening (arrows) in systole and diastole, suggestive of both volume and pressure overload of the right ventricle (RV). The left ventricle (LV) appears small and hyperdynamic.

diagnosis for thrombus in the right heart includes congenital structures, such as a Chiari network or eustachian valve, or acquired structures, such as cardiac tumors or vegetations (see Chapter 19).

As direct visualization of the thrombus is unusual, one must rely on visualization of indirect manifestations of an acute PE on the heart. The RV normally faces little resistance as it empties into the low-pressure

Chiari Network Eustachian Valve

Apical 4-Chamber

Fig. 5. Apical four-chamber view from patient in Figs. 3 and 4 demonstrates an enlarged and severely hypokinetic right ventricle (RV) with moderate tricuspid regurgitation (arrow). (Please see companion DVD for corresponding video.)

Chiari Network Echo Images
Fig. 6. Continuous-wave Doppler from the same patient in Figs. 3-5 demonstrates mild elevation of peak tricuspid velocity regurgitant velocity (3.0 m/s), which corresponds to a pulmonary artery systolic pressure of 37 mmHg plus right atrial pressure.

system of the normal pulmonary vasculature. When faced with acute obstruction to outflow, as occurs in acute PE, right ventricular function may not be able to compensate and the RV begins to fail as evidenced by enlargement and hypokinesis (Figs. 3-6; please see companion DVD for corresponding video for Fig. 5). The degree of dysfunction relates to the size and severity of the PE. The RV is often dilated with a right ventricular end-diastolic diameter in the parasternal long-axis view of more than 27 mm. The apical four-chamber view may also demonstrate right ventricular enlargement as evidenced by a right ventricular to left ventricular end-diastolic diameter ratio greater than the normal ratio of 0.6. In addition to right ventricular hypokinesis and enlargement, the intraventricular septum

Fig. 7. Apical four-chamber demonstrates a characteristic regional right ventricular dysfunction (McConnell's sign) characterized by a severely hypokinetic free wall of the right ventricle, but a "spared" right ventricular apex. Note the markedly dilated right ventricular cavity. (Please see companion DVD for corresponding video.)

Hypokinetic Right Ventricle

Fig. 7. Apical four-chamber demonstrates a characteristic regional right ventricular dysfunction (McConnell's sign) characterized by a severely hypokinetic free wall of the right ventricle, but a "spared" right ventricular apex. Note the markedly dilated right ventricular cavity. (Please see companion DVD for corresponding video.)

may be flattened or show leftward displacement as a result of the volume and/or pressure overload of the RV. Additionally, paradoxical septal motion may be visualized. Because of septal displacement, the left ventricular cavity size is often diminished and there may be Doppler evidence of impairment of diastolic left ventricular filling.

In addition to global dysfunction, a characteristic two-dimensional echocardiography finding of regional right ventricular dysfunction has been described in patients with acute PE. This abnormality is characterized by the presence of normal or hyperdynamic wall motion of the right ventricular apex despite moderate or severe right ventricular free-wall hypokinesis (McConnell sign) (Fig. 7; please see companion DVD for corresponding video). This sign appears quite specific for the diagnosis of acute PE (specificity 94%), and, thus, may be useful to distinguish between right ventricular dysfunction owing to other cause such as pulmonary hypertension (Fig. 8).

In addition to echocardiographic abnormalities of the RV, other indirect echocardiographic manifestations are visualized. The right atria and the inferior vena cava may be dilated, with diminished normal respiratory variation of the inferior vena cava suggesting elevated right-sided pressures. The peak TR velocity may be mildly increased (>2.7 m/s) as a result of increased PASP, although the peak TR velocity often does not increase acutely to a significant degree, as the normal RV is unable to generate significantly elevated pressures. The pulmonary ejection acceleration time, measured in the right ventricular outflow tract, may be shortened (<80 m/s).

In general, the sensitivity of TTE for the diagnosis of an acute pulmonary embolus has been estimated to be between 50 and 60% with a specificity of 80-90%. Overall, approx 40-50% of patients with acute PE have echocardiography evidence of right ventricular hypo-kinesis. In those with massive PE, echocardiography evidence of PE may be seen in up to 80% of patients. Because of this finding, TTE is often helpful in the differential diagnosis of the hemodynamically compromised individual, but the diminished overall sensitivity of TTE for the diagnosis of PE limits the utility of echocardiography as a screening tool for all patients with this suspected disorder.

Several studies have suggested that transesophageal echocardiography (TEE) may have increased sensitivity over TTE in the detection of a pulmonary embolus (Fig. 9; please see companion DVD for corresponding video). Using TEE, the main pulmonary artery and the right pulmonary artery are better visualized, but visualization of the left pulmonary artery, as a result of the interposition of the left main pulmonary bronchus, and visualization of the distal pulmonary vasculature is limited. In patients with a clinical suspicion of PE and right

Atrium Deformity Worm

Fig. 8. Effects of pulmonary embolus on the right ventricle. The normal right ventricle (RV; A) is accustomed to low pulmonary resistance. Normal right ventricular pressures are low and compliance is high, with small changes in pressure resulting in large changes in volume. Unlike the left ventricle (LV), the normal RV does a poor job at acutely responding to sudden increases in after-load. Pulmonary embolism (PE) results in an increase in pulmonary vascular resistance. A previously normal RV is unable to acutely accommodate this additional load. The RV dilates (B) but cannot acutely increase pressure. Depending on the size of the PE, this can result in mild right ventricular strain or frank right ventricular failure.

Fig. 8. Effects of pulmonary embolus on the right ventricle. The normal right ventricle (RV; A) is accustomed to low pulmonary resistance. Normal right ventricular pressures are low and compliance is high, with small changes in pressure resulting in large changes in volume. Unlike the left ventricle (LV), the normal RV does a poor job at acutely responding to sudden increases in after-load. Pulmonary embolism (PE) results in an increase in pulmonary vascular resistance. A previously normal RV is unable to acutely accommodate this additional load. The RV dilates (B) but cannot acutely increase pressure. Depending on the size of the PE, this can result in mild right ventricular strain or frank right ventricular failure.

Plax Echocardiogram
Fig. 9. Images of the right atrium on the midesophageal transesophageal echocardiography views demonstrate a mobile, worm-like thrombus (arrows). (Please see companion DVD for corresponding video.)
Parasternal Long Axis Volume Overload
Fig. 10. Parasternal long-axis (PLAX) views of the same patient (Figs. 3-6) 1 d following thrombolysis shows improvement— although still impaired—of right ventricular function.

ventricular overload by TTE, the sensitivity of TEE was 80% with a specificity of 97%. Because of the inability of TEE to visualize the distal vasculature, the diagnostic accuracy in patients without evidence of right ventricular overload remains unclear. Despite its limitations, transesophageal allows for the investigation of patients who may be hemodynamically unstable and cannot have other tests such as computed tomography scan, nuclear perfusion studies, or pulmonary angiography, although it may be of limited value in acutely ill patients.

Adult Echo Short Axis View
Fig. 11. Parasternal short-axis (PSAX) views of the same patient as in Fig. 9.

With chronic PE many of the previously described echocardiography findings may be seen. Additionally, right ventricular hypertrophy and more significantly increased PASPs may also be seen as the RV adapts to chronic PE.

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