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Approach to a Dilated Right Ventricle
Approach to a Dilated Right Ventricle ( For the beginners )
Dr (Col) S K Parashar.
The right ventricle ( RV ) is no longer considered as a neglected chamber, because numerous studies have shown its prognostic significance in various cardiovascular diseases like congenital lesions, pulmonary hypertension, myocardial infarction, left ventricular (LV) dysfunction etc.. The RV is anatomically placed beneath the sternum and anteriorly positioned to the left ventricle ( LV ). The muscle mass of RV is approximately one-sixth that of LV, as it pumps blood against approximately one-sixth the resistance of LV. As compared to LV, the RV is thin walled ( approx. 3-4 mm ). The normal RV is accustomed to a low pulmonary resistance and hence a low after load. As such normal RV pressure is low and has a high compliance. The RV is therefore sensitive to changes in after load. As such RV enlargement occurs in response to chronic pressure and / or volume overload and also any cause leading to RV failure like RV infarction or dysphasia. Echocardiography assessment of RV is limited by (a) complex geometry of the chamber (b) pronounced trabeculations that compromise accurate endocrinal delineation (a) anterior position that often limits echo image quality. Owing to incomplete visualization of the RV in a single 2-D echo view, all possible scan planes need to be projected for a comprehensive evaluation of RV. This paper is mainly focused for level 1/2 echo cardiographers.
What constitutes an RV enlargement: This can be (a) quantitative (b) qualitative Various workers have proposed quantitative parameters to assess RV enlargement. However the problem is that there is a lack of fixed reference points to ensure optimization of RV. Depending upon the cut planes there can be significant variation in measured dimensions and is mostly underestimated. As such it has been proposed to obtain a focused RV view to concentrate on the lateral wall of RV. In this view (Fig. 1), the 4-chamber view is readjusted to focus on the RV rather than LV. It should be ensured that RV is not foreshortened. If one is able to get the desired view then two important measurements of RV are (a) the maximal short axis dimension in basal 1/3 of the ventricular cavity (b) longitudinal dimension from tricuspid annulus to RV apex. Diameter more than 42 mm at base and > 86 mm longitudinal dimension indicate RV enlargement. However the RV dimensions can be distorted and falsely enlarged in patients with chest and thoracic spine deformities. Qualitative: Based on the above limitations and from a day to day practical point of view, a qualitative assessment is usually performed. Qualitatively the RV is smaller, and no more than 2/3 of LV in 4 chamber view. If RV appears larger than LV in this view then it is significantly enlarged (Fig. 2). Furthermore as RV enlarges it may displace the LV and form the apex – ‘apex forming ventricle’. This may indicate moderate RV enlargement but this finding has not been validated quantitatively. Visually the RV / LV end diastolic diameter ratio is ≥ 1.0 in cases of RV enlargement.
Consultant Cardiologist & Director,
Non Invasive Cardiac Laboratory. Metro Hospitals & Heart Institute, Delhi.
E-mail: drparashar@yahoo.com
Mobile : 09810146231