Alterations in left ventricular dimensions and mural force following coronary occlusion

Abstract

In open-chest dogs, left ventricular mural force was recorded with a strain-gage arch was placed essentially in series with the myocardial fibers and measured the force necessary to hold the 2 edges of a myocardial incision in approximation. Abrupt occlusion of the anterior descending coronary artery in each of 8 experiments was followed by a marked increase in force recorded from the ischemic region (mean + 115% [plus or minus] SE 5.8%). Simultaneous recordings with an isotonic arch demonstrated a bulging of the ischemic region during systole and provided an estimate of the changes in internal radius (Ri) of the bulging of the ischemic region during systole and provided an estimate of the changes in internal radius (Ri) of the bulging segment. An index of the distending forces (PRi2) was calculated from recordings of left ventricular pressure (LVP) and relative values of Ri. Close correlations between force recorded by the gage (F) and PRi2 were shown for the period of isovolumic systole. Com parison of maximum LVP and Ri indicated that LVP was not significantly altered by occlusion, while Ri was significantly increased. These findings support the view that the systolic changes of the bulging ischemic region of the left ventricle are predominantly responses to the forces defined (F = [pi]PR2).