[On the mechanism of valve plane (author's transl)]

A detailed description of the functional sequence and mechanism of the valve plane movements is given as an extension of the studies on the functional morphology of cardiac movements. The valve plane mechanism is driven in the small, rapidly beating heart by the contraction of the external and internal spiral fibres of the myocardium which decreases the width of the chamber. The atrium is enlarged during systole by the descent of the valvular ring towards the apex. The auricular apendices must act as a compensation reservoir giving the atrial wall the necessary freedom of movement within the pericardial dome. Under these working conditions (hypovolaemia, decreased venous return pathophysiological consequences are discernible as subendocardial bleeding secondary to increased sliding movement of the inner layer of the myocardium against the middle layer. Chamber dilation as a consequence of endocardial fibrosis is explained as a result of progressive rigidity of endo-epicardial fixation. These structural changes progressively impair the systolic-diastolic changes in wall thickness.