Page 21 - Rotation of the base
This diagram is a suggestion that the ventricular mass may be subject to rotation by the fact that there is a bias to the right atrial side in the attachments of the great vessels to the base of the heart. Given that the pulmonary arteries are immobile and the main pulmonary artery is inelastic, right ventricular myocytes in the line of the right ventricular outflow tract (long green arrow) could well produce a clockwise movement in the atrioventricular ring.
Flow across the aortic valve is a consideration. It could be that its inertial effect is to drive the aortic valve upward, and this would also give a slight clockwise rotation.
When the heart is exposed at surgery it does appear to rotate clockwise (as viewed from the apex), click here to see a video of it. However it may well be the case that this motion is exaggerated by the pericardium being open. In the intact normal the heart does not move in so obvious a manner, click here to see a cine CT sequence. (You can also click here for a short document which links to more videos.)