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

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 degrees 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 end-systolic 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 less than 0.001). The mean systolic IVS thickness increased symmetrically from 7.43 +/- 0.55 mm to 12.49 +/- 0.39 mm (p less than 0.001). In brief, the IVS thickens on its transverse axis and shortens on its longitudinal axis, contributing equally to RV and LV function.