The ventricular septum: the lion of right ventricular function, and its impact on right ventricular restoration.

OBJECTIVE To evaluate the structure-function relationships of the right ventricle (RV) and septum and determine if the helical ventricular band model would define fiber orientation for maximal force response. Implications were made for right ventricular function. METHODS The right ventricular free wall and biventricular septum were studied by inserting sonomicrometer crystals at different angulations to determine the maximum response of fiber shortening. These reactions were compared to the lateral left ventricular (LV) wall and further tested by use of positive and negative inotropic drug infusions. RESULTS The maximum contraction of the free wall was achieved by placing crystals in the transverse orientation angulations, whereas oblique orientation allowed the maximal septal response. Fiber orientation angulation was the same for the LV free wall and septum. These angulations correlate with the MRI-related twisting actions of septal motion needed for ejection and suction for rapid filling. These findings have important impact, because they imply that the septum is 'lion of right ventricular function,' since septal twisting is essential when pulmonary vascular resistance is increased. The incidence of postoperative right heart failure due to septal dyssyncrony, with loss of septal twisting action from inadequate myocardial protection, is explored relative to RV free wall and septum function. Furthermore, early studies of right ventricular restoration in patients with RV dysplasia and RV failure after chronic pulmonary insufficiency following repair of Tetralogy of Fallot are described, with predominant attention directed toward rebuilding normal septal architecture and function. CONCLUSIONS This experimental and clinical overview indicates that the septum is 'the lion of right ventricular function,' and implies that the use of this knowledge can become an important guideline for planning novel surgical geometric interventions after RV failure.