Myocardial protection during coronary angioplasty with autoperfusion and forced perfusion: an in vitro comparison

During coronary angioplasty, perfusion distal to the inflated angioplasty balloon can be maintained with autoperfusion balloon catheters and coronary perfusion pumps. The blood flow rates through the autoperfusion balloon catheters and the flow rates achieved with a perfusion pump were compared in vitro with fresh human blood at 37 degrees C. In a specially designed system, blood flow rates through StackTM autoperfusion balloon catheters were measured at 40, 60 and 80 mmHg continuous pressure. In another system, driving pressures were measured during perfusion with the pump, through a specially designed forced perfusion catheter at 20, 40 and 60 ml/min flow. The pressure applied in the autoperfusion experiments was converted into atmospheres (atm) to facilitate comparison with the driving pressures measured during pumping (1 mmHg = 1.316 x 10(-3) atm). Mean flow rates through the autoperfusion balloon catheters were: 46 ml/min at 0.05 atm, 66 ml/min at 0.09 atm and 75 ml/min at 0.1 atm. Mean pressures during pumping were: 1.8 atm at 20 ml/min, 3.5 atm at 40 ml/min, 5 afm at 60 ml/min. Due to the phasic nature of coronary blood flow, the flow through autoperfusion balloons is generally lower than the minimum required for adequate myocardial protection (= 60 ml/min). Thus, autoperfusion balloon catheters are simpler and cheaper devices than perfusion pumps, but generally they are not able to provide adequate myocardial protection.