IN-VITRO EVALUATION OF BLOOD-FLOW THROUGH AUTOPERFUSION BALLOON CATHETERS

The effective flow rates with human blood through an autoperfusion cat heter cannot be monitored in vivo and have not been experimentally det ermined in vitro. The manufacturers (Advanced Cardiovascular Systems [ ACS], Temecula, CA) have suggested that ''the flow rate'' through the Stack(TM) over the wire and the RX-60(TM) monorail catheter is 60 ml/m in with a pressure gradient of 80 mmHg. We measured human blood flow r ates in vitro through these catheters under different continuous press ure regimens (between 40 and 120 mmHg), with varying hematocrit levels (between 25% and 62%). Measured blood flows at a gradient of 80 mmHg were found to vary from 32 to 65 cc/min, with hematocrit levels of 62- 25%. Minor variations in the circuitry, besides the viscosity of the m edium, cause significant changes in observed flow rates (such as kinki ng of the catheter and blood sedimentation). In vitro determinations o f blood flows cannot automatically be transferred to the in vivo condi tion, primarily because in vitro determinations do not account for the systolic intramural pressure increase (which may overcome the aortic pressure). If such a phenomenon is also considered, then the in vitro flow rates reported here should be multiplied by a factor of 0.40-0.60 to determine effective in vivo flow rates. Such information is releva nt for the clinical operator of angioplasty, especially in the treatme nt of patients at high risk for undergoing percutaneous transluminal c oronary angioplasty. (C) 1993 Wiley-Liss, Inc.