Cardiac Surgery in Acute Myocardial Infarction: Crystalloid versus Blood Cardioplegia

Introduction: Because hearts in acute myocardial infarction are probably more prone to ischemia-reperfusion damage during cardiac surgery than stable hearts with intact coronary circulation, we investigated the influence of crystalloid cardioplegia solution (CCP) and blood cardioplegia solution (BCP) on cardiac function, metabolism, and infarct size in an in vitro rat heart model of myocardial infarction.

Material and methods: Following euthanasia, the hearts of 32 male Wistar rats (Janvier, St. Berthevin, France) were quickly excised, cannulated, and inserted into a blood-perfused isolated heart apparatus. A regional myocardial infarction was created in the infarction group (16 hearts) for 120 minutes the control group (16 hearts) did not undergo ligation. In each group, either Buckberg BCP or Bretschneider CCP was administered in 8 hearts for an aortic clamping time of 90 minutes. During reperfusion, functional parameters were recorded: coronary blood flow, left ventricular developed pressure (LVDP), and contractility (dp/dt max), oxygen consumption and lactate production. Infarct size was determined by planimetry using the Leica Application Suite LAS.

Results: Cardiac function after acute myocardial infarction and 90 min of cardioplegic arrest was better preserved with Buckberg BCP than with Bretschneider CCP (LVDP 60 ± 10% of baseline vs. 9 ± 4% of baseline, dp/dt max. 65 ± 8% of baseline vs. 24 ± 3% of baseline), while coronary flow was similarly impaired (BCP 66 ± 18% BL, CCP 57 ± 20% BL). The infarct pattern was different between BCP and CCP: While in BCP, the infarct size was small (25% of myocardium) and limited to the area of LAD ligation, in CCP, the infarct size was bigger (48% of myocardium) and myocardial necrosis was unevenly distributed to the left ventricular wall: 51% of the hearts expressed an inner layer ischemia, in 49% of the hearts, other areas than the LAD ligation area were ischemic.

Conclusions: In acute rat myocardial infarction followed by cardioplegic arrest, BCP leads to better myocardial recovery than CCP.

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