Abstract 16478: Total Left Ventricular Unloading Strikingly Reduces the Infarct Size in Ischemia Reperfusion
Background: Imbalance of oxygen supply and demand is one of the essential mechanisms of ischemia. Left ventricular (LV) assist device (VAD) unloads LV and reduces myocardial oxygen consumption (MVO2). However, how the degree of LV unloading impacts on the infarct size in acute ischemia remains unknown.
Theoretical consideration: We define the partial-unloading where both LV and VAD eject, while the total-unloading where only VAD ejects. The partial-unloading reduces preload, whereas increases cardiac output and mean arterial pressure (MAP), thereby increases afterload. This is to say that the partial-unloading may not decrease much the LV pressure-volume area (PVA), an index of MVO2. In contrast, the total-unloading markedly decreases preload and afterload, and thus MVO2. We hypothesized the total-unloading would markedly decrease the infarct size compared with the partial-unloading.
Method: We allocated 13 anesthetized dogs into 3 groups, CONT (no support, n=5), PARTIAL (LV output equals LVAD flow, n=4) and TOTAL support (no LV output, n=4). Each group was exposed to ischemia by occluding major branches of the left anterior descending coronary artery for 90 minutes and reperfused for the following 5 hours. We assessed the infarct size (normalized by the risk area) at the end of the perfusion.
Results: MAP did not differ among 3 groups (CONT: 91±6.1, PARTIAL: 92±8,5 and TOTAL: 102±7.1 mmHg). In TOTAL, LV peak-systolic pressure (32±8.4 mmHg) was much lower than MAP, indicating LV no longer ejected. VAD significantly reduced the infarct size (CONT: 43±2.4, PARTIAL: 25±3.3, and TOTAL: 5.0±1.6%). However, TOTAL reduced the infarct size relative to control by 88%, which was by far larger than PARTIAL. Changes in CK-MB paralleled those in the infarct size.
Conclusion: TOTAL unloading is vital to maximize the impact of VAD in reducing the infarct size.
- © 2013 by American Heart Association, Inc.