The use of all-blood miniplegia provided superior protection when compared to global ischemia or crystalloid cardioplegia in acutely ischemic hearts. The model employed is very close to the clinical situation due to the use of blood as a perfusate.

Objective: To develop an isolated working heart model with parabiotic circulation in swine and to verify its stability and possibility for allowing effective measurements of hemodynamic and metabolic data.Methods: This model was developed during an association study of cardiolegia agents. Eighteen experiments were performed, each with a support animal and a donor animal. Donor animal heart was perfused as isolated working heart with parabiotic circulation from the support animal. The isolated heart underwent regional ischemia by interventricular artery clamping, followed by global ischemia. During reperfusion in a isolated heart in working state at 30, 60, and 90 minutes, contractility indices such as elastance, preload recruitable stroke work index, and metabolic data were acquired.Results: Support animals were kept stable throughout the procedures without use of blood transfusions or vasoactive drugs. Variables such as pH, oxygen partial pressure and hematocrit were kept stable and within physiologic ranges. The isolated heart was perfused adequately throughout the experiment. All hemodynamic and metabolic data proposed were adequately measured in the isolated heart in working state.Conclusion: This isolated swine "working heart" model was kept stable throughout the experiments with no administration of vasoactive drugs, and it allowed adequate measurements of metabolic and hemodynamic data.Descriptors: Heart/surgery. Models, animal. Swine. Cardioplegic solutions. Cardiac surgical procedures. Myocardial reperfusion/methods. 15SILVEIRA FILHO, LM ET AL -Development of isolated swine "working heart model" with parabiotic circulation Bras Cir Cardiovasc 2008; 23(1): 14-22 Rev

Análise do perfil hidrodinâmico em diferentes modelos de bombas de rolete utilizadas em circulação extracorpóreaAnalysis of the hydrodynamic profile in different roller pumps models used in cardiopulmonary bypass Abstract Objective: Among the equipments used in cardiopulmonary bypass the roller pumps have great importance with various models available from several manufacturers. The calibration is an important factor in hemolysis rates and its potential is different in each. Researchers do not always approach details on the pump bed profiles assuming that the standardized calibration settings ensure equal and comparable values for all models of roller pumps. We have mainly two methods for calibration of pumps which also interferes on the hemolytic potential. In both of them, the characteristics of fluid impulsion defined by the pump bed design are not considered. The aim of this study is to compare the hydrodynamic profile of three models of roller pumps available in the Brazilian market.Method: The rollers occlusion was performed by measures of drop and dynamic calibration. Two different silicone diameter tubes were used (3/8 x 1/16 and 1/2 x 3/32 inches).Results: The profiles showed differences in their variances, P<0.01 for drop rate measures and P<0.0001 for dynamic calibration. Different changes in pressure were found between the pumps analyzed (P<0.002).

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In the present study we standardized an experimental model of parabiotic circulation of isolated pig heart. The isolated heart was perfused with arterial blood from a second animal as support and submitted to regional ischemia for 30 min, followed by total ischemia for 90 min and reperfusion for 90 min. Parameters for measurement of ventricular performance using different indices measured directly or indirectly from intraventricular pressure were defined as: maximum peak pressure, final diastolic pressure, pressure developed, first derivative of maximum pressure (dP/dt max ), first derivative of minimum pressure (dP/dt min ), systolic stress of the left ventricle (s s ), and maximum elastance of the left ventricle. Isolated hearts subjected to regional and global ischemia presented significant worsening of all measured parameters. Less discriminative parameters were dP/dt max and dP/ dt min . Elastance was the most sensitive parameter during the reperfusion period, demonstrating an early loss of ventricular function during reperfusion. The model proved to be stable and reproducible and permitted the study of several variables in the isolated heart, such as ischemia and reperfusion phenomena, the effects of different drugs, surgical interventions, etc. The model introduces an advantage over the classical models which use crystalloid solutions as perfusate, because parabiotic circulation mimics heart surgery with extracorporeal circulation.