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Assessment of Right Ventricular Function


The right ventricle (RV) is often overlooked because most cardiologists focus their attention on the left ventricle (LV). Early work characterizing ventricular anatomy and physiology was performed on the LV and then assumed to be similar in the RV. Methods for measuring ventricular volume and function from the various imaging modalities were similarly developed for the LV and then applied to the RV. However, more recent studies have gradually revealed the differences between the two ventricles, and interest in the RV has risen because of recognition of the impact of RV dysfunction on patient prognosis, the increasing survival of patients with congenital heart disease to adulthood, and the rising incidence of pulmonary hypertension. Although the complex shape of the RV has long been recognized, it could previously only be glimpsed from two-dimensional (2D) images; the recent advent of three-dimensional (3D) surface reconstruction techniques for the RV has enabled new appreciation for the variety of phenotypes in which the RV can present in various conditions ( Figure 13-1 ).

Figure 13-1
Three-dimensional reconstructions of the right ventricle showing the variety of phenotypes. Top, right to left, The diagnoses are normal, double-outlet right ventricle after Rastelli repair, idiopathic dilated cardiomyopathy, Ebstein's anomaly, and repaired truncus arteriosus with conduit from the right ventricle to the pulmonary artery. Bottom, left to right, The diagnoses are pulmonary hypertension from connective tissue disease, criss-crossed heart, repaired tetralogy of Fallot, repaired tetralogy of Fallot, and pulmonary atresia with ventricular septal defect after Rastelli repair. The view is from the septum with the pulmonary valve to the left and tricuspid valve to the right, except for an inferior view of the ventricle with the tricuspid valve in the foreground in the patient with cardiomyopathy.

Visualization of the Right Ventricle

The sector width in current ultrasound equipment is too narrow to contain both the LV and RV. Therefore, when acquiring the ultrasound study, it is necessary to ensure that the RV is completely visualized. This is easily accomplished by centering the view on the RV in both parasternal ( Figure 13-2 ) and apical views ( Figure 13-3 ). Additional nonstandard views may be needed in patients with RV dilation. The four-chamber view can visualize the cardiac apex in normal hearts. However, centering of the RV is needed to visualize the apical bulging that may occur in hemodynamic overload states (see Figure 13-3 ).

Figure 13-2, Visualization of the right ventricle (RV) in parasternal views. All views are shown in original form ( left ) with annotation ( center ), and as a three-dimensional reconstruction ( right ) of the RV illustrating the anatomic position of the view plane and the RV contour (in yellow ). The patient has tetralogy of Fallot with wide-open pulmonary regurgitation after repair; the RV end-diastolic volume index is 132 mL/m 2 . A1-3, RV-centered short-axis (SAX) view at mid-level angulated to visualize the free wall ( arrow ) within the sector. B1-3, Basal SAX view angulated to visualize RV inflow. C1-3, Basal SAX view angulated to visualize RV outflow. D1-3, Modified SAX view to visualize RV outflow. E1-3, RV centered long-axis (LAX) view. F1-3, LAX view rotated to visualize RV inflow. G1-3, LAX view rotated to visualize RV outflow. Ao , aorta; LV , left ventricle; PA , pulmonary artery; PB , parietal band; PV, pulmonary valve; TV, tricuspid valve; RA , right atrium.

Figure 13-3, Visualization of the right ventricle (RV) in apical views shown in original form ( left ) with annotation ( center ), and as a three-dimensional reconstruction ( right ) of the RV illustrating the anatomic position of the view plane and the RV contour (in yellow ) A1-3, RV-centered four-chamber (4C) view. B1-3, Sweeping anteriorly from the 4C view reveals the RV free wall between the valves. C1-3, Acquisition of the 4C view from a medial position may improve visualization of the apical free wall ( arrow ). D1-3, The anterior sweep from the 4C view, taken from a medial transducer position, may improve visualization of the free wall between the valves. E1-3, View of both inflow and outflow regions. The apex ( not seen ) is at the upper right. LV, left ventricle; PA, pulmonary artery; PB, parietal band; RA, right atrium.

Volume Measurement

Two-Dimensional Approaches

The RV is notorious for its complex shape, which defies comparison with a geometric reference figure. In contrast, LV volume can be accurately measured from single or biplane views by comparison with an ellipsoid of revolution using the area-length method. Early attempts to measure RV volume from angiograms used the formula V = k A 1 A 2 /L, where A 1 and A 2 are the areas of the RV in the two views, L is the length of the RV long axis, and k is a constant. Depending on the value of k and how L is defined, the RV was compared with a parallelepiped, ellipsoid of revolution (area-length method), triangular prism, or pyramid. When these methods were compared with in vitro hearts or models, the disk summation method proved to be the most accurate. The area-length method also performed well from the projection views of angiograms but proved inaccurate on 2D echocardiograms.

Models that take advantage of ultrasound's tomographic, rather than projection, imaging were also developed. Levine and colleagues wrote: “A geometric structure can be constructed resembling the right ventricle with respect to its overall form and body segment, and such a structure can have a volume equal to 2AL/3 without unreasonable restriction of its dimensions,” where A is the area in one view and L spans the RV in the other, roughly orthogonal view ( Figure 13-4 ). However, these models require subcostal views that may be obtainable in only 52% of patients older than 5 years.

Figure 13-4, Geometric models with volume = 2AL/3. PV, pulmonary valve; TV, tricuspid valve.

Because of the inaccuracy in volume measurement, assessment of right ventricular ejection fraction (RVEF) based on 2D echocardiography (2DE) is not recommended. Instead, visual assessment is performed to gauge RV size relative to that of the LV ( Figure 13-5 ; Video 13-1 ). Normally, the RV is only two thirds the size of the LV in the apical four-chamber view; the LV forms the apex of the heart and is round in short-axis views throughout the cardiac cycle. Deviations from this pattern may indicate RV dilation, but careful examination of multiple views is recommended for confirmation of the diagnosis because the size of the RV varies with the angle of the plane ( Figure 13-6 ).

Figure 13-5, Video image of a normal echocardiogram from the apical four-chamber view. The area of the right ventricle is smaller than that of the left ventricle on visual inspection, in accordance with their end-diastolic volume indexes (86.3 mL/m 2 and 99.5 mL/m 2 , respectively). The right ventricular ejection fraction is 51% (see Video 13-1).

Figure 13-6, The recommended apical four-chamber (A4C) view with focus on the right ventricle ( RV, 1* ) and the sensitivity of RV size with angular change ( 2, 3 ) despite similar size and appearance of the left ventricle ( LV ). The lines of intersection of the A4C planes ( 1*, 2, 3 ) with a mid–LV short axis are shown above with corresponding A4C views below.

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