Interventricular septal motion: Biventricular angiographic assessment of its relative contribution to left and right ventricular contraction

Abstract

The interventricular septum (IVS) has conventionally been regarded as a functional part of the left ventricle (LV). To determine its normal range of motion, simultaneous biventricular cineangiograms (60 frames/sec) were performed (60° left anterior oblique) in nine subjects without coronary or other heart disease. Arrhythmias were avoided by using a specially designed right ventricular (RV) angiographic catheter. IVS motion was studied qualitatively by three observers and quantitatively by superimposing end-systolic and diastolic frames using intra- and extracardiac reference points. Two transverse chords that trisected the endsystolic length of the IVS were drawn to quantitate IVS, LV and RV free wall motion. Qualitatively, the IVS thickened toward both RV and LV cavities as a result of shortening on its longitudinal axis. LV motion was 39.9±7.2% on the transverse axis, of which 31.2±5.2% was contributed by the LV free wall and 8.5±2.1% by IVS. RV transverse axis motion was 36.9±3.7%, of which 28.6±2.1% was contributed by the RV free wall and 8.3±2.3% by IVS motion. There was no difference between IVS motion toward the LV and that toward the RV. The IVS longitudinal axis shortened by 17.4±2.8% (p<0.001). The mean systolic IVS thickness increased symmetrically from 7.43±0.55 mm to 12.49±0.39 mm (p<0.001). In brief, the IVS thickens on its transverse axis and shortens on its longitudinal axis, contributing equally to RV and LV function.