Transmural changes in fibre helix angle in normal and failing canine ventricles

Fibre orientation relative to the base-apex axis (the helix angle) varies across the ventricular wall. The aim of this study was to examine the consistency of transmural helix angle in 6 normal canine hearts, and 3 canines with heart failure from the Johns Hopkins DT-MRI dataset. In the normal hearts, the helix angle across the LV free wall and septum changed smoothly from between 50° and 60° in the epicardial layer (RV endocardium in the septum) to between -50° and -60° in the LV endocardial layer. However, we observed abrupt changes in helix angle abrupt and within an endocardial layer around 3 mm thick. Close to the insertion of the RVand the septum, fibre orientation was much more variable. In failing hearts, changes in helix angle across the LV and RV free walls as well as the septum was much less well defined. Our findings indicate that the helix angle is more variable close to the ventricular endocardium, at the insertion of the RV, and in failing hearts.