DECREASE IN FORCES RESPONSIBLE FOR DIASTOLIC SUCTION DURING ACUTE CORONARY-OCCLUSION

Background The production of left ventricular (LV) restoring forces ge nerated during contraction, which are responsible for diastolic suctio n, is dependent on end-systolic volume (ESV) and systolic transmural a nd 3D deformation. We tested the hypothesis that acute coronary occlus ion would result in loss of forces that cause suction. Methods and Res ults Ten open-chest dogs were subjected to a 10-minute acute coronary occlusion (proximal left anterior descending coronary artery). A servo motor connected to the left atrium (LA) was used to rapidly clamp LA p ressure during systole below the level of the succeeding LV diastolic pressure, resulting in nonfilling diastoles during which the LV fully relaxed at its ESV. LA clamps at multiple ESVs (conductance catheter) allowed delineation of positive and negative portions of the fully rel axed LV pressure-volume relation (FRPVR). A negative fully relaxed pre ssure (FRP) indicates the presence of restoring forces. After 10 minut es of acute coronary occlusion, there was an upward shift of the FRPVR . Thus, for example, at matched ESVs before and during coronary occlus ion, FRP was -1.1+/-1.1 (+/-SD) mm Hg before versus 0.2+/-1.2 mm Hg af ter 10 minutes of coronary occlusion (P<.05). Conclusions Acute corona ry occlusion results in a rapid decrease in forces responsible for suc tion. This phenomenon is independent of the level of ESV and may contr ibute to ischemic diastolic dysfunction.