Anatomy of the right ventricle
The right ventricle is the most anterior cardiac chamber and is delimited by the annulus of the tricuspid valve and by the pulmonary valve. Its primary function is to receive systemic venous return and to pump it into the pulmonary arteries with the same stroke volume as the left ventricle. Because of its complex geometry and its anterior position, the right ventricle remains difficult to investigate by echocardiography.
The right ventricle is the most anterior cardiac chamber, immediately located behind the sternum. It delineates the inferior border of the cardiac silhouette.
- The shape of the right ventricle is complex. In contrast to the ellipsoidal shape of the left ventricle, the right ventricle is triangular when viewed longitudinally and is crescent shaped when viewed transversally.
- Its complex shape is difficult to model geometrically as opposed to the left ventricle, which explains the difficulty to assess right ventricular volumes and function by echocardiography.
- Traditionally, the right ventricle is divided into 2 parts: an inflow portion named “the sinus” and an outflow portion named “the conus” separated by the crista supraventricularis.
- As opposed to this traditional description, Goor and Lillehei  described three anatomic and functional subunits: the inlet (from the tricuspid valve annulus to the proximal infundibulum), the apical trabecular (the right ventricular body to the apex), and the outlet (also called infundibulum or conus, from the right ventricular outflow tract to the pulmonary valve).
For anatomy of the valve, see Anatomy of tricuspid valve.
Nomenclature of the right ventricular walls
- The current international guidelines  recommend the following segmentation of the right ventricular walls: anterior, inferior and lateral walls.
- The right ventricle also shares the septal wall with the left ventricle.
- Each wall can be divided into 3 segments: basal, mid and apical.
- The lateral wall is also commonly named "right ventricular free wall”.
Right ventricular mass
The right ventricle muscle mass is approximately one-sixth that of the left ventricle because of different loading conditions. Indeed, the right ventricle pumps against approximately one-sixth the resistance of the left ventricle.
Trabeculations and muscular bands
As opposed to the normal left ventricle, the right ventricle is highly trabeculated and present several muscle bands including 3 prominent muscular bands.
- The parietal band: the parietal band and the infundibular septum formed toghether the crista supraventricularis.
- The septomarginal band: extends inferiorly and becomes continuous with the moderator band, which attaches to the anterior papillary muscle.
- The moderator band.
The musculature of the right ventricle extends from the atrioventricular to the ventriculo-arterial junctions.
- The inflow portion of the right ventricle is mainly composed of circumferential fibres in the subepicardium and longitudinal fibers in the subendocardium.
- The outflow portion of the right ventricle is composed of both subendocardial and subepicardial fibres running longitudinally, overlaid by fibres running at right angle to the outlet long axis in a circumferentially, which can be traced to the crista supraventricularis and to the anterior ventricular sulcus, serving to bind the two ventricles together.
- Because of the orientation of the right ventricular fibers, global assessment of the right ventricle is difficult, with the two main sections contracting perpendicular to each other: the inflow portion longitudinally and the outflow portion circumferentially.
How to recognize the right ventricle from the left ventricle
Although the right ventricle is usually located on the right side of the heart and connects with the pulmonary circulation, the anatomic right ventricle is defined by its structure rather than by its position or connections. The main morphological differences between the right ventricle from the left ventricle are the following:
- the more apical position of the septal leaflet of the tricuspid valve as compared to the anterior leaflet of the mitral valve;
- the presence of a moderator band;
- the presence of more than 3 papillary muscles;
- the three leaflets of the atrio-ventricular (tricuspid) valve with septal papillary attachments;
- the absence of fibrous continuity between the ventriculo-arterial (tricuspid) valve and the atrio-ventricular (pulmonary) valve;
- the presence of trabeculations (trabeculations can also be seen in the left ventricle in case of pathological non-compaction of the left ventricle).
- The primary function of the right ventricle is to receive systemic venous return and to pump it into the pulmonary arteries.
- Under normal circumstances, the right ventricle is connected in series with the left ventricle and is, therefore, obligated to pump on average the same effective stroke volume.
- Because of lower pulmonary resistance as compared to systemic resistance, right ventricular wall is thinner that left ventricular wall. The thin-walled and compliant right ventricle facilitates quick adaptation to changes in preload.
- Normal right ventricular contraction proceeds in a sequential manner, as a peristaltic wave directed from inflow tract to infundibulum. Longitudinal shortening is the major contributor to the right ventricular performance with an equal contribution of the right ventricular longitudinal wall and the interventricular septum.
Assessment of the right ventricle by bidimensional echocardiography
As recommended by the current international guidelines, multiple echocardiographic views are required in order to explore the right ventricle. The different views potentially useful to assess the right ventricle are the following:
Parasternal long axis view
This view is highly variable view and therefore, not sufficient. It might be helpful for the measurement of the right ventricular wall thickness and the right ventricular outflow dimension.
Parasternal long axis view of right ventricular outflow and pulmonary artery
- Assessment of the anterior right ventricular outflow tract in its long-axis view with infundibular segment, the pulmonary valve, and main pulmonary artery.
- Measurement of pulmonary annular dimension.
Parasternal long-axis view of right ventricular inflow
Assessment of anterior and inferior right ventricular walls, anterior and posterior tricuspid valve leaflets, anterior and posterior papillary muscles, chordal attachment, ostium of inferior vena cava including the Eustachian valve.
Parasternal short axis of right ventricle at the basal level
- Assessment of basal anterior right ventricular wall, right ventricular outflow tract, tricuspid and pulmonary valves and right atrium.
- Measurement of right ventricular outflow tract dimension in diastole.
- Assessment of the interatrial septum for shunt.
Parasternal short axis of basal right ventricle of bifurcation of the pulmonary artery
- Assessment of the pulmonary valve, pulmonary artery and its branches, proximal and distal right ventricular outflow tract segments.
- Measurement of the pulmonary annulus dimension, pulmonary artery size.
Parasternal short axis at mitral valve level
- Assessment of basal level of anterior, inferior and lateral walls.
- Septal flattening / eccentric index of the left ventricle (right ventricular volume or pressure overload).
Parasternal short axis at papillary muscle level
- Assessment of mid level of anterior, inferior and lateral walls.
- Septal flattening / eccentric index of the left ventricle (right ventricular volume or pressure overload).
Apical 4-chamber view
- Size, shape and function of the right ventricle.
- Measurements of maximal long-axis distance and minor distances of the right ventricle at base and mid-level.
- Measurements of systolic function parameters.
Right ventricular focused apical 4-chamber view
- Alternative to the classic apical 4-chamber view.
- Enhance visualization of the lateral wall.
Right ventricular modified apical 4-chamber view
- Provide information about a portion of the lateral wall.
- Assessment of atrial shunt.
Right ventricular apical 5-chamber view
- Assessment of anterolateral wall and moderator band.
Apical coronary sinus view
- Assessment of posterolateral wall and coronary sinus.
- Measurement of right ventricular wall thickness.
- Right ventricular inversion/collapse (cardiac tamponade).
- Assessment of atrial shunts (Atrial septal defect and Permeable Foramen Ovale).
- No quantification of the right ventricular size.
Subcostal short-axis of basal right ventricle
- Base of the right ventricular wall, right ventricular inflow, outflow, pulmonary valve, pulmonary artery and its branches.
- Right ventricular outflow tract dimension can also be measured in this view.
Tridimensional echocardiography assessment of the right ventricle is promising but routine clinical use is limited by the need for excellent quality transthoracic data sets for accurate analysis with software packages.
Assessment of right ventricular dimensions
Right ventricular wall thickness
The right ventricular wall thickness can be measured at end-diastole by M-mode or 2D echocardiography preferably from the subcostal window, at the level of the tip of the anterior tricuspid leaflet or possibly from the left parasternal windows. Abnormal right ventricular wall thickness should be reported using the normal cutoff of 5 mm from either parasternal long-axis or subcostal windows, specially in patients suspected of having right ventricular and/or left ventricular dysfunction.
Right ventricular dimensions
Measurements of right ventricular basal, mid cavity, and longitudinal dimensions should be performed on a 4-chamber view. The upper reference limit for the right ventricular basal dimension is 42 mm, mid dimension is 35 mm, and longitudinal dimension 86 mm. The most common and easy measurement is to compare the relative size of the right ventricle with that of the left ventricle. The right ventricle may be described as dilated despite measuring within the normal range, on the basis of a right ventricle significantly larger than the left ventricle.
Right ventricular outflow tract dimensions
In studies on select patients with congenital heart disease or arrhythmia potentially involving the right ventricular outflow tract, proximal and distal diameters of the right ventricular outflow tract measurement from the parasternal short axis and long axis views are recommended.  The parasternal short axis distal right ventricular outflow tract diameter, just proximal to the pulmonary annulus, is the most reproducible. For select cases such as suspected arrhythmogenic right ventricular cardiomyopathy, the parasternal long axis measure may be added. The upper reference limit for the parasternal short axis distal right ventricular outflow tract diameter is 27 mm and for parasternal long axis is 33 mm.
Assessment of right ventricular area, volumes and global systolic function
- ↑ Goor, D. & Lillehei, C. Congenital malformations of the heart. Congenital Malformations of the Heart: Embryology, Anatomy, and Operative Considerations 1–37 (1975)