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16.4 Right ventricular volume overload

Several conditions may lead to right ventricular volume overload. The most common cause is tricuspid regurgitation, followed by atrial septal defects and pulmonary regurgitation. Coronary fistulas (into the right heart) are another rare cause of this condition. Its pathology and echocardiographic appearance will be discussed in the respective chapters. This section will deal with the effects of volume overload on the right ventricle.

16.4.1 Echocardiographic features of right ventricular volume overload

Right ventricular volume overload is characterized by dilatation of the right ventricle and hyperdynamic right ventricular function.

Severe tricuspid regurgitation causing right ventricular volume overload
Dilated right ventricle in severe tricuspid regurgitation after tricuspid valve endocarditis

Right ventricular volume overload can be tolerated for extended periods of time. However, like the left ventricle the right ventricle will also eventually fail. Right ventricular dilatation results in tricuspid annular dilatation and tricuspid regurgitation. This triggers a vicious circle by way of even greater volume overload. Right ventricular volume overload may be suspected when moderate/severe tricuspid regurgitation is present or when atrial septal defects are large. Right ventricular dilatation can be established by several quantification techniques as well as by comparing the size of the right ventricle with that of the left one. Besides, the apex will be formed by the right ventricle.
An important additional finding is abnormal motion of the interventricular septum. In volume overload the septum will move towards the left during diastole and "flatten". As a result, the left ventricle is "D-shaped". As mentioned in the previous section, the time of septal flattening (systole or diastole) determines whether pressure or volume overload (or both) is/are present.

Abnormal septal motion and D-shaped ventricle in right ventricular volume overload (TR)

Aside from establishing the presence and cause of volume overload, echocardiography helps to determine the functional status of the right ventricle. This is probably one of the most difficult problems in echocardiography. Yet it is very important as regards the timing of surgery (i.e. tricuspid and pulmonary regurgitation); the latter should be performed before right ventricular function is irreversibly impaired. Echocardiography has its limitations when it comes to quantifying right ventricular function (see Chapter 3, Chambers and Walls). In case of uncertainty one may have to perform cardiac MRI in order to quantify right ventricular function.

Right ventricular function is almost always impaired when patients with RV volume overload have symptoms of right heart failure (e.g. pleural effusion or peripheral edema).