Burn-Induced Impairment of Cardiac Contractile Function Is Due to Gut-Derived Factors Transported in Mesenteric Lymph

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Abstract
Neither the source nor the cause of burn-induced myocardial dysfunction is known. Because scald burns have been shown to cause cardiac contractile dysfunction, the purpose of this study was to test the hypothesis that gut-derived myocardial depressant factors were responsible for burn-induced cardiac contractile dysfunction. Male rats were subjected to laparotomy with or without mesenteric lymph duct ligation (LDL). After LDL or sham-LDL, the rats were randomized to receive sham or scald burn (43% TBSA full thickness) after which they were resuscitated for 24 h with 4 mL/kg/%burn of Ringer's lactate solution, and then killed, and the hearts removed. Cardiac function was assessed by measuring the left ventricular pressure (LVP) and maximal rate of LVP rise and fall (±dP/dt) in response to increases either in 1) preload, 2) coronary flow rate, or 3) perfusate calcium. At 24 h after burn or sham burn and before killing, the mean arterial pressure of the burn group was less than the burn + LDL or the sham burn groups (P < 0.05). Pre-burn LDL significantly prevented burn-induced depression in LVP and ±dP/dt (P < 0.05). In addition, the hearts harvested from the burn group showed a significant impairment in contraction and relaxation when preload, coronary flow, or perfusate calcium was increased compared with the burn + LDL and sham groups (P < 0.05). Burn-induced cardiac dysfunction, manifested by impaired contraction and relaxation, is prevented by pre-burn lymph duct ligation. These results indicate that gut-derived myocardial depressant factors transported in mesenteric lymph contribute to burn-induced impairment of cardiac contractile function, because burn-induced cardiac dysfunction can be totally abrogated by pre-burn mesenteric lymph duct ligation.