Myocardial contractile function in porcine hearts perfused with media containing erythrocytes or perfluoro-octylbromide
Haas N., Stewart LC., Clarke K., Tian GH., Scott J., Biro GP., Deslauriers R.
The many similarities between porcine and human hearts have led us to develop the Langendorff-perfused pig heart as a model for studying cardiac function and metabolism. The purpose of the present work was to evaluate the potential of a perfluorooctylbromide-based emulsion (PFOB) as an oxygen carrier. Isolated pig hearts were perfused with either washed porcine erythrocytes (10% hct) (RBC), modified Krebs-Henseleit (KH) solution or PFOB (4:1 v/v KH:PFOB) (Alliance Pharmaceuticals). Contractile function was assessed by the rate-pressure product (heart rate × developed pressure, RPP) measured using a fluid-filled latex balloon fixed in the left ventricle and pacing the heart at 96 beats/min. Hearts perfused with PFOB had 30% higher RPP values than those perfused with RBC or KH at 100 mmHg pressure. Thus, at 100 mmHg perfusion pressure, PFOB sustains cardiac function better than do crystalloid solutions, largely owing to the contribution to O 2 delivery of PFOB. The effect on the RPP of varying the coronary perfusion pressure from 100 to 30 mmHg in steps of 10 mmHg was evaluated using the three test perfusates. Studies of KH-perfused hearts, using 31 P nuclear magnetic resonance (NMR) to continuously evaluate high energy phosphate levels, have shown that at a perfusion head pressure ≥ 60 mmHg (2.5 mL/min/g), the levels of phosphate metabolites were constant, whereas decreases in phosphocreatine and increases in Pi became apparent at lower pressure heads. In PFOB hearts reducing pressure head to below 60 mmHg (coronary flow < 1.0 ml/min/g) led to accumulation of the PFOB within the vasculature. In KH and RBC perfused hearts, raising the perfusion pressure head from 30 to 100 mmHg increased coronary flow to that seen initially at the same pressure and RPP recovered to 60% of the initial value. In contrast, the flow in PFOB hearts was similar to the initial value and RPP recovery was ≥ 75%.