P1799Importance of the parietal band in normal subjects and in patients with repaired tetralogy of Fallot: the unknown muscle of the forgotten ventricle

Abstract

Abstract Introduction The parietal band (PB) is little acknowledged. The PB traverses the basal part of the right ventricle (RV) with myocardial fibres circumscribing the inlet portion of the RV, anatomical studies suggest the PB may be of significant importance for RV contraction. RV dysfunction is of particular concern in patients with repaired Tetralogy of Fallot (ToF pts.). Purpose To study the importance of the PB for RV function in a retrospective cohort study by comparison of normal subjects with ToF pts. with and without resected PB. Methods The PB function was compared to RV volume and function by echocardiography and magnetic resonance imaging (CMR) in 89 normal subjects (echo and CMR) and 106 ToF pts. (CMR). Results A PB was identified in all normal subjects. In these, the PB shortened by 41±5% (mean±SD) during systole, and correspondingly, the septum-to-free wall distance was shortened by 47±17%. In ToF pts., the PB had been resected in 57.5% of cases. Resection of the PB was not of any consequence for RV dilatation or pulmonary and tricuspid valve regurgitation fraction (all ns), but resection was associated with a lowered RV free-wall to inter-ventricular septum approximation (21±13% vs. 39±9%) and consequently a lowered RV ejection fraction (RVEF; 45±8% vs. 54±8%) (both p<0.001). 84% vs. 48% (p<0.0001) had reduced RVEF if the PB had been resected. Conclusions The two groups of ToF pts. may differ in other aspects than presence of the parietal band, but taken together our findings in normal subjects and ToF pts. do suggest that the parietal band is significant importance for right ventricle contraction.