Dynamics of the interventricular septum and ventricular free walls during regional ischaemia in open-chest dogs.

The significance of ischaemia of the left ventricular (LV) and right ventricular (RV) free walls for the dynamics of the interventricular septum (IVS) and the right ventricle was examined in open-chest dogs. Left ventricular and RV ischaemia reduced stroke volume similarly, by 11.2 +/- 1.4% and 11.2 +/- 2.4%, respectively. The dynamics of myocardial segment lengths (SL), recorded in the LV and RV free walls and the IVS, differed. During LV ischaemia, end-diastolic SL (EDSL) and systolic shortening (SS) increased in the IVS, whereas SL remained unchanged in the RV free wall. During RV ischaemia, LV EDSL, and SS decreased. Interventricular septum EDSL also decreased, but this reduction was not statistically significant. During blood volume expansion, LV and RV function curves were shifted right, and/or downwards by LV ischaemia, whereas only the RV function curve was shifted downwards and to the right by RV ischaemia. Thus, ischaemia of the LV free wall induces activation of the Frank-Starling mechanism in the interventricular septum and a deterioration of right ventricular performance.