Mechanical left ventricular unloading prior to reperfusion reduces infarct size in a canine infarction model.

We tested the hypothesis that unloading the left ventricle just prior to reperfusion provides infarct size reduction compared with left ventricular (LV) unloading postreperfusion and reperfusion alone. Twenty-four mongrel dogs were subjected to 2 hr of left anterior descending artery occlusion and 4 hr of reperfusion. A transvalvular (TV) left ventricular assist device (LVAD) was inserted just prior to reperfusion and maintained during the rest of the experiment (LV Assist Pre group). In the LV Assist Post group, the TV LVAD was inserted and activated just after reperfusion. A control group was subjected to reperfusion alone with a sham-TV LVAD. At baseline, the hemodynamic data were similar in the three groups. Myocardial infarct size expressed as percentage of area at risk was significantly reduced in the LV Assist Pre group compared to the control group (P = 0.011) and to the LV Assist Post group (P < 0.05). At 4 hr of reperfusion, transmural myocardial blood flow in the ischemic zone was slightly higher in the animals unloaded prior to reperfusion compared to controls and significantly higher than in the LV Assist Post group (P = 0.04). Postreperfusion end-diastolic wall thickness returned to baseline level in the TV LV Assist Pre group compared to both controls and TV LV Assist Post group. In these latter two groups, a significant increase in postreperfusion end-diastolic wall thickness and contraction band necrosis in the central ischemic zone correlated well with the degree of reperfusion injury. LV unloading prior to, but not after, reperfusion reduces the extent of myocardial necrosis in canine hearts subjected to 2 hr of left anterior descending artery occlusion and 4 hr of reperfusion compared to either reperfusion alone or LV unloading after reperfusion.